U.S. patent application number 13/213172 was filed with the patent office on 2011-12-15 for security system for generating keys from access rules in a decentralized manner and methods therefor.
This patent application is currently assigned to Guardian Data Storage, LLC. Invention is credited to Denis Jacques Paul Garcia, Hal S. Hildebrand.
Application Number | 20110307937 13/213172 |
Document ID | / |
Family ID | 44455544 |
Filed Date | 2011-12-15 |
United States Patent
Application |
20110307937 |
Kind Code |
A1 |
Hildebrand; Hal S. ; et
al. |
December 15, 2011 |
SECURITY SYSTEM FOR GENERATING KEYS FROM ACCESS RULES IN A
DECENTRALIZED MANNER AND METHODS THEREFOR
Abstract
Improved system and approaches for decentralized key generation
are disclosed. The keys that can be generated include both public
keys and private keys. The public keys are arbitrary strings that
embed or encode access restrictions. The access restrictions are
used to enforce access control policies. The public keys are used
to encrypt some or all portions of files. The private keys can be
generated to decrypt the portions of the files that have been
encrypted with the public keys. By generating keys in a
decentralized manner, not only are key distribution burdens
substantially eliminated but also off-line access to encrypted
files is facilitated.
Inventors: |
Hildebrand; Hal S.; (Moss
Beach, CA) ; Garcia; Denis Jacques Paul; (Palo Alto,
CA) |
Assignee: |
Guardian Data Storage, LLC
Wilmington
DE
|
Family ID: |
44455544 |
Appl. No.: |
13/213172 |
Filed: |
August 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10246079 |
Sep 17, 2002 |
8006280 |
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13213172 |
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10075194 |
Feb 12, 2002 |
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10246079 |
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60339634 |
Dec 12, 2001 |
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Current U.S.
Class: |
726/1 |
Current CPC
Class: |
G06F 21/6218 20130101;
H04L 9/0825 20130101; H04L 9/3226 20130101 |
Class at
Publication: |
726/1 |
International
Class: |
G06F 17/00 20060101
G06F017/00 |
Claims
1. A method for encrypting a file, said method comprising:
obtaining access rules to be imposed; producing a rules string in
accordance with the access rules; generating a public key based on
the rules string; and encrypting at least a portion of the file
using the public key.
2-27. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-In-Part (CIP) of U.S.
patent application Ser. No. 10/075,194, filed Feb. 12, 2002, and
entitled "SYSTEM AND METHOD FOR PROVIDING MULTI-LOCATION ACCESS
MANAGEMENT TO SECURED ITEMS," which is hereby incorporated by
reference for all purposes, and which claims priority of U.S.
Provisional Application No. 60/339,634, filed Dec. 12, 2001, and
entitled "PERVASIVE SECURITY SYSTEMS," which is hereby incorporated
by reference for all purposes.
[0002] This application is also related to: (i) U.S. application
Ser. No. 10/186,203, filed Jun. 26, 2002, and entitled "METHOD AND
SYSTEM FOR IMPLEMENTING CHANGES TO SECURITY POLICIES IN A
DISTRIBUTED SECURITY SYSTEM," which is hereby incorporated by
reference for all purposes; (ii) U.S. patent application Ser. No.
10/206,737, filed Jul. 26, 2002, and entitled "METHOD AND SYSTEM
FOR UPDATING KEYS IN A DISTRIBUTED SECURITY SYSTEM," which is
hereby incorporated by reference for all purposes; (iii) U.S.
patent application Ser. No. 10/159,537, filed May 31, 2002, and
entitled "METHOD AND APPARATUS FOR SECURING DIGITAL ASSETS," which
is hereby incorporated by reference for all purposes; and (iv) U.S.
patent application Ser. No. 10/074,825, filed Feb. 12, 2002, and
entitled "METHOD AND APPARATUS FOR ACCESSING SECURED ELECTRONIC
DATA OFF-LINE," which is hereby incorporated by reference for all
purposes.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to security systems for data
and, more particularly, to security systems that protect data in an
inter/intra enterprise environment.
[0005] 2. Description of Related Art
[0006] The Internet is the fastest growing telecommunications
medium in history. This growth and the easy access it affords have
significantly enhanced the opportunity to use advanced information
technology for both the public and private sectors. It provides
unprecedented opportunities for interaction and data sharing among
businesses and individuals. However, the advantages provided by the
Internet come with a significantly greater element of risk to the
confidentiality and integrity of information. The Internet is an
open, public and international network of interconnected computers
and electronic devices. Without proper security means, an
unauthorized person or machine may intercept any information
traveling across the Internet and even get access to proprietary
information stored in computers that interconnect to the Internet,
but are otherwise generally inaccessible by the public.
[0007] There are many efforts in progress aimed at protecting
proprietary information traveling across the Internet and
controlling access to computers carrying the proprietary
information. Cryptography allows people to carry over the
confidence found in the physical world to the electronic world,
thus allowing people to do business electronically without worries
of deceit and deception. Every day hundreds of thousands of people
interact electronically, whether it is through e-mail, e-commerce
(business conducted over the Internet), ATM machines, or cellular
phones. The perpetual increase of information transmitted
electronically has lead to an increased reliance on
cryptography.
[0008] One of the ongoing efforts in protecting the proprietary
information traveling across the Internet is to use one or more
cryptographic techniques to secure a private communication session
between two communicating computers on the Internet. The
cryptographic techniques provide a way to transmit information
across an unsecure communication channel without disclosing the
contents of the information to anyone eavesdropping on the
communication channel. Using an encryption process is a
cryptographic technique whereby one party can protect the contents
of the data in transit from access by an unauthorized third party,
yet the intended party can read the data using a corresponding
decryption process.
[0009] A firewall is another security measure that protects the
resources of a private network from users of other networks.
However, it has been reported that many unauthorized accesses to
proprietary information occur from the inside, as opposed to from
the outside. An example of someone gaining unauthorized access from
the inside is when restricted or proprietary information is
accessed by someone within an organization who is not supposed to
do so. Due to the open nature of the Internet, contractual
information, customer data, executive communications, product
specifications, and a host of other confidential and proprietary
intellectual property remain available and vulnerable to improper
access and usage by unauthorized users within or outside a
supposedly protected perimeter.
[0010] Many businesses and organizations have been looking for
effective ways to protect their proprietary information. Typically,
businesses and organizations have deployed firewalls, Virtual
Private Networks (VPNs), and Intrusion Detection Systems (IDS) to
provide protection. Unfortunately, these various security means
have been proven insufficient to reliably protect proprietary
information residing on private networks. For example, depending on
passwords to access sensitive documents from within often causes
security breaches when the password of a few characters long is
leaked or detected. Consequently, various cryptographic means are
deployed to provide restricted access to electronic data in
security systems.
[0011] Various security criteria, such as encryption or decryption
keys, are often used to facilitate the restricted access in the
security systems. However, prolonged use of the security criteria,
if not updated, can impose threats to the security of the protected
data. While periodic updates to keys can help preserve security,
the generation and distribution of key (such as in a network-based
system) is a significant burden to system resources. When the
system maintains a large number of keys for numerous file and
users, the demand of system resources is even more taxing.
Therefore, there is a need to provide more effective ways to
utilize the security criteria (e.g. the keys) for security systems
to secure and protect resources.
SUMMARY OF THE INVENTION
[0012] The invention relates to improved approaches for
decentralized key generation. The keys that can be generated
include both public keys and private keys. The public keys are
arbitrary strings that embed or encode access restrictions. The
access restrictions are used to enforce access control policies.
The public keys are used to encrypt some or all portions of files.
The private keys can be generated to decrypt the portions of the
files that have been encrypted with the public keys. By generating
keys in a decentralized manner, not only are key distribution
burdens substantially eliminated but also off-line access to
encrypted files is facilitated.
[0013] The invention can be implemented in numerous ways, including
as a method, system, device, and computer readable medium. Several
embodiments of the invention are discussed below.
[0014] As a method for encrypting a file, one embodiment of the
invention includes at least the acts of: obtaining access rules to
be imposed; producing a rules string in accordance with the access
rules; generating a public key based on the rules string; and
encrypting at least a portion of the file using the public key.
[0015] As another method for encrypting a file, one embodiment of
the invention includes at least the acts of: identifying access
rules to be imposed; producing a rules string in accordance with
the access rules; obtaining a key block of the file to be
encrypted, the file including at least the key block and a data
block; generating a public key for the key block based on the rules
string; and encrypting the key block portion of the file using the
public key.
[0016] As a method for decrypting a secured file that has been
previously encrypted, one embodiment of the invention includes at
least the acts of: obtaining a key string associated with the
secured file to be decrypted; identifying access rules associated
with the key string; evaluating the access rules to determine
whether a user requesting access to the secured file is permitted
access to the secured file; denying access to the secured file when
said evaluating determines that the access rules do not permit the
user to access the secured file; generating a private key based on
the access rules and a master key when said evaluating determines
that the access rules permit the user to access the secured file;
and decrypting, following said generating, at least a portion of
the secured file for access thereto by the user through use of the
private key.
[0017] As another method for decrypting a secured file that has
been previously encrypted, one embodiment of the invention includes
at least the acts of: obtaining a key string associated with the
secured file to be decrypted; identifying access rules associated
with the key string; obtaining an encrypted key block of the
secured file; evaluating the access rules to determine whether a
user requesting access to the secured file is permitted access to
the secured file; denying access to the secured file when said
evaluating determines that the access rules do not permit the user
to access the secured file; generating a private key based on the
access rules and a master key when said evaluating determines that
the access rules permit the user to access the secured file;
decrypting, following said generating, the encrypted key block to
obtain a file key; and thereafter decrypting at least a portion of
the secured file for access thereto by the user through use of the
file key.
[0018] As a computer readable medium including at least computer
program code for encrypting a file, one embodiment of the invention
includes at least: computer program code for obtaining access rules
to be imposed; computer program code for producing a rules string
in accordance with the access rules; computer program code for
generating a public key based on the rules string; and computer
program code for encrypting at least a portion of the file using
the public key.
[0019] As a computer readable medium including at least computer
program code for decrypting a secured file that has been previously
encrypted, one embodiment of the invention includes at least:
computer program code for obtaining a key string associated with
the secured file to be decrypted; computer program code for
identifying access rules associated with the key string; computer
program code for evaluating the access rules to determine whether a
user requesting access to the secured file is permitted access to
the secured file; computer program code for denying access to the
secured file when said evaluating determines that the access rules
do not permit the user to access the secured file; computer program
code for generating a private key based on the access rules and a
master key when said evaluating determines that the access rules
permit the user to access the secured file; and computer program
code for decrypting at least a portion of the secured file for
access thereto by the user through use of the private key.
[0020] Other objects, features, and advantages of the present
invention will become apparent upon examining the following
detailed description of an embodiment thereof, taken in conjunction
with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
wherein:
[0022] FIG. 1A shows a basic system configuration in which the
invention may be practiced in accordance with an embodiment
thereof.
[0023] FIG. 1B shows another system configuration in which the
invention may be practiced in accordance with an embodiment
thereof.
[0024] FIG. 1C shows still another system configuration in which
the invention may be practiced in accordance with an embodiment
thereof.
[0025] FIG. 1D shows internal construction blocks of a computing
device in which the invention may be implemented and executed.
[0026] FIG. 2A is a block diagram of securing a created document
according to one embodiment of the invention.
[0027] FIG. 2B illustrates an exemplary structure of a secured
document including a header and an encrypted portion.
[0028] FIG. 3A illustrates a representative data structure of a
secured file including a header and an encrypted data portion
according to one embodiment of the invention.
[0029] FIG. 3B is a functional block diagram of a server device in
accordance with one embodiment of the invention.
[0030] FIG. 3C is a functional block diagram of a local server
device according to one embodiment of the invention.
[0031] FIG. 3D is a functional block diagram of a client machine
according to one embodiment of the invention.
[0032] FIG. 4 is a block diagram of a file security system
according to one embodiment of the invention.
[0033] FIG. 5 is a block diagram of a distributed file security
system according to one embodiment of the invention.
[0034] FIG. 6 is a flow diagram of access rules based encryption
processing according to one embodiment of the invention.
[0035] FIG. 7 is a flow diagram of access rules based decryption
processing according to one embodiment of the invention.
[0036] FIG. 8 is a flow diagram of access rules based encryption
processing according to another embodiment of the invention.
[0037] FIG. 9 is a flow diagram of access rules based decryption
according to another embodiment of the invention.
[0038] FIG. 10 illustrates flow diagrams of an authorization
process according to one embodiment of the invention.
[0039] FIG. 11 shows a flowchart of a user authentication process
that may be implemented in a server, such as an access server, a
central server or a local server.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The invention relates to improved approaches for
decentralized key generation. The keys that can be generated
include both public keys and private keys. The public keys are
arbitrary strings that embed or encode access restrictions. The
access restrictions are used to enforce access control policies.
The public keys are used to encrypt some or all portions of files.
The private keys can be generated to decrypt the portions of the
files that have been encrypted with the public keys. By generating
keys in a decentralized manner, not only are key distribution
burdens substantially eliminated but also off-line access to
encrypted files is facilitated. The present invention is
particularly suitable in an enterprise environment.
[0041] As used herein, a user may mean a human user, a software
agent, a group of users, a member of the group, a device and/or
application. Besides a human user who needs to access a secured
document, a software application or agent sometimes needs to access
secured files in order to proceed. Accordingly, unless specifically
stated, the "user" as used herein does not necessarily pertain to a
human being.
[0042] Secured files are files that require one or more keys,
passwords, access privileges, etc. to gain access to their content.
According to one aspect of the present invention, the security is
provided through encryption and access rules. The files, for
example, can pertain to documents, multimedia files, data,
executable code, images and text. In general, a secured file can
only be accessed by authenticated users with appropriate access
rights or privileges. Each secured file is provided with a header
portion and a data portion, where the header portion contains, or
points to, security information. The security information is used
to determine whether access to associated data portions of secured
files is permitted.
[0043] In the following description, numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. However, it will become obvious to those skilled
in the art that the present invention may be practiced without
these specific details. The description and representation herein
are the common meanings used by those experienced or skilled in the
art to most effectively convey the substance of their work to
others skilled in the art. In other instances, well-known methods,
procedures, components, and circuitry have not been described in
detail to avoid unnecessarily obscuring aspects of the present
invention.
[0044] Reference herein to "one embodiment" or "an embodiment"
means that a particular feature, structure, or characteristic
described in connection with the embodiment can be included in at
least one embodiment of the invention. The appearances of the
phrase "in one embodiment" in various places in the specification
are not necessarily all referring to the same embodiment, nor are
separate or alternative embodiments mutually exclusive of other
embodiments. Further, the order of blocks in process flowcharts or
diagrams representing one or more embodiments of the invention do
not inherently indicate any particular order nor imply any
limitations in the invention.
[0045] Embodiments of the present invention are discussed herein
with reference to FIGS. 1A-11. However, those skilled in the art
will readily appreciate that the detailed description given herein
with respect to these figures is for explanatory purposes as the
invention extends beyond these limited embodiments.
[0046] FIG. 1A shows a basic system configuration in which the
present invention may be practiced in accordance with one
embodiment thereof. Documents or files may be created using an
authoring tool executed on a client computer 100, which may be a
desktop computing device, a laptop computer, or a mobile computing
device. Exemplary authoring tools may include application programs
such as Microsoft Office (e.g., Microsoft Word, Microsoft
PowerPoint, and Microsoft Excel), Adobe FrameMaker and Adobe
Photoshop.
[0047] According to one embodiment, the client computer 100 is
loaded with a client module that is capable of communicating with a
server 104 or 106 over a data network (e.g., the Internet or a
local area network). According to another embodiment, the client
computer 100 is coupled to the server 104 through a private link.
As will be further explained below, a document or file created by
an authoring tool can be secured by the client module. The client
module, when executed, is configured to ensure that a secured
document is secured at all times in a store (e.g., a hard disk or
other data repository). The secured documents can only be accessed
by users with proper access privileges. In general, an access
privilege or access privileges for a user may include, but not be
limited to, privileges pertaining to viewing, copying, printing,
editing, transferring, uploading/downloading, and location.
[0048] According to one embodiment, a created document is caused to
go through an encryption process that is preferably transparent to
a user. In other words, the created document is encrypted or
decrypted under the authoring application so that the user is not
aware of the process. A key (referred to herein as a user key) can
be used to retrieve a file key to decrypt an encrypted document.
Typically, the user key is associated with an access privilege for
the user or a group of users. For a given secured document, only a
user with a proper access privilege can access the secured
document.
[0049] In one setting, a secured document may be uploaded via the
network 110 from the computer 100 to a computing or storage device
102 that may serve as a central repository. Although not necessary,
the network 110 can provide a private link between the computer 100
and the computing or storage device 102. Such link may be provided
by an internal network in an enterprise or a secured communication
protocol (e.g., VPN and HTTPS) over a public network (e.g., the
Internet). Alternatively, such link may simply be provided by a
TCP/IP link. As such, secured documents on the computer 100 may be
remotely accessed.
[0050] In another setting, the computer 100 and the computing or
storage device 102 are inseparable, in which case the computing or
storage device 102 may be a local store to retain secured documents
or receive secured network resources (e.g., dynamic Web contents,
results of a database query, or a live multimedia feed). Regardless
of where the secured documents or secured resources are actually
located, a user, with proper access privilege, can access the
secured documents or resources from the computer 100 or the
computing or storage device 102 using an application (e.g.,
Internet Explorer, Microsoft Word or Acrobat Reader).
[0051] The server 104, also referred to as a local server, is a
computing device coupled between a network 108 and the network 110.
According to one embodiment, the server 104 executes a local
version of a server module. The local version is a localized server
module configured to service a group of designated users or client
computers, or a location. Another server 106, also referred to as a
central server, is a computing device coupled to the network 108.
The server 106 executes the server module and provides centralized
access control management for an entire organization or business.
Accordingly, respective local modules in local servers, in
coordination with the central server, form a distributed mechanism
to provide distributed access control management. Such distributed
access control management ensures the dependability, reliability
and scalability of centralized access control management undertaken
by the central server for an entire enterprise or a business
location.
[0052] FIG. 1B shows another system configuration in which the
invention may be practiced in accordance with an embodiment
thereof. Here, the configuration employs a central server and local
servers. The configuration may correspond to a large enterprise
having multiple geographic locations or offices. A central server
106 maintains a database managing the access privileges and the
access rules in the entire enterprise. One of the features in this
configuration is the underlying capability to provide fault
tolerance and efficient AC (Access Control) management for a large
group of users. Instead of having the central server 106 performing
the AC management for each of the users at one single location, a
number of local servers 104 (e.g., 104-A, 104-B, . . . and 104-N)
are employed in a distributed manner to service the individual
locations or offices. Each of local servers 104 executes a local
module derived or duplicated from the server module being executed
at the central server 106 to manage those users who are local to
respective local servers 104. The central server 106 can centralize
the AC management in addition to managing the users if
necessary.
[0053] According to one embodiment, a local module can be a
customized version of the server module that runs efficiently for
only a few locations or a group of users. For example, a local
server 104-A is only responsible for the users or computers 102-A
in location A, while a local server 104-B is only responsible for
the users or computers 102-B in location B. As a result, even if
the central server 106 has to be taken down for maintenance or is
not operative at the time a user needs to access secured documents,
the access control will not be disrupted. The detailed operation of
the local servers 104 in cooperation with the central server 106
will be further described below.
[0054] According to another embodiment, a local module is a
replicated version of the server module and exchanges any updates
with the server module when connected (e.g., periodically or at
request). Depending on implementation, part or all of the server
module can be duplicated in a local server to ensure that
communications with users or their client machines are efficient
and fault tolerance. As a result, even if the central server 106
has to be taken down for maintenance or is not operative at the
time a user needs to access secured documents, the access control
will not be disruptive. For example, in such a situation, any of
the local servers 104 can step up and take the place of the central
server. When the central server 106 is running or communicating
with the local servers 104, information collected at the respective
local servers about the users or their activities is sent back to
the central server 106. The detailed operation of the local servers
104 in cooperation with the central server 106 in this regard will
also be further provided below.
[0055] FIG. 1C shows still another system configuration in which
the invention may be practiced in accordance with an embodiment
thereof. This configuration is suitable for a small group of users.
In this configuration, no local servers are employed. A server
computer 112 is loaded with the server module and each of the users
or terminal computers 116 (only one is shown therein) is loaded
with a client module. The users or the terminal computers 16 couple
to the server computer 112 through a local area network. The server
computer 112 performs the AC management for each of the users or
the terminal computers 116.
[0056] FIG. 1D shows internal construction blocks of a computing
device 118 in which one embodiment of the present invention may be
implemented and executed. The computing device 118 may correspond
to a client device (e.g., computer 100, computing or storage device
102 in FIG. 1A) or a server device (e.g., server 104, 106 in FIG.
1A). As shown in FIG. 1B, the computing device 118 includes a
central processing unit (CPU) 122 interfaced to a data bus 120. The
CPU 122 executes instructions to process data and perhaps manage
all devices and interfaces coupled to data bus 120 for synchronized
operations. The instructions being executed can, for example,
pertain to drivers, operating system, utilities or applications.
Device interface 124 may be coupled to an external device, such as
the computing device 102 of FIG. 1A; hence, the secured documents
therefrom can be received into memory 132 or storage 136 through
data bus 120. Also interfaced to data bus 120 is a display
interface 126, a network interface 128, a printer interface 130 and
a floppy disk drive interface 138. Generally, a client module, a
local module or a server module of an executable version of one
embodiment of the present invention can be stored to storage 136
through floppy disk drive interface 138, network interface 128,
device interface 124 or other interfaces coupled to data bus 120.
Execution of such module by the CPU 122 can cause the computing
device 118 to perform as desired in the present invention. In one
embodiment, the device interface 124 provides an interface for
communicating with a capturing device 125 (e.g., a fingerprint
sensor, a smart card reader or a voice recorder) to facilitate the
authentication of a user of the computing device 118.
[0057] Main memory 132, such as random access memory (RAM), is also
interfaced to data bus 120 to provide the CPU 122 with instructions
and access to memory storage 136 for data and other instructions.
In particular, when executing stored application program
instructions, such as for document securing or document accessing,
the CPU 122 is caused to manipulate the data to achieve results
contemplated by the program instructions. Read-only memory (ROM)
134 is provided for storing executable instructions, such as a
basic input/output operation system (BIOS) for operation of
keyboard 140, display 126 and pointing device 142 which may be
present.
[0058] In one embodiment, the computing device 118 is capable of
storing secured items (e.g., secured files) in the main memory 132
or the storage 136. The main memory 132 provides non-persistent
(i.e., volatile) storage for the secured items and the storage 136
provides persistent (i.e., non-volatile) storage for the secured
items. Hence, the computing or storage device 102, or more
particularly, the main memory 132 and/or the storage 136, can act
as a storage device for the secured items.
[0059] Referring now to FIG. 2A, a block diagram of securing a
created document 200 is shown according to one embodiment of the
invention. For example, the created document 200 is a created file.
After the document 200 is created, edited or opened with an
application or authoring tool (e.g., Microsoft Word), upon an
activation of a command, such as "Save," "Save As" or "Close", or
automatic saving invoked by an operating system, the application
itself or an approved application, the created document 200 is
caused to undergo a securing process 201. The securing process 201
starts with an encryption process 202, namely the document 200 that
has been created or is being written into a store is encrypted by a
cipher (e.g., an encryption process) with a file key (i.e., a
cipher key), in other words, the encrypted data portion 212 could
not be opened without the file key. For the purpose of controlling
the access to the contents in the document 200 or the resultant
secured file 208, the file key or keys may be the same or different
keys for encryption and decryption and are included as part of
security information contained in or pointed to by a header 206.
The file key or keys, once obtained, can be used to decrypt the
encrypted data portion 212 to reveal the contents therein.
[0060] To ensure that only authorized users or members of an
authorized group can access the secured file 208, a set of access
rules 204 for the document 200 is received or created and
associated with the header 206. In general, the access rules 204
determine or regulate who and/or how the document 200, once
secured, can be accessed. In some cases, the access rules 204 also
determine or regulate when or where the document 200 can be
accessed.
[0061] In addition, security clearance information 207 can be added
to the header 206 if the secured file 208 is classified. In
general, the security clearance information 207 is used to
determine a level of access privilege or security level of a user
that is attempting to access the contents in the secured file 208.
For example, a secured file may be classified as "Top secret",
"Secret", "Confidential", and "Unclassified". According to one
embodiment, the security clearance information 207 includes another
layer of encryption of the file key with another key referred to
herein as a clearance key. An authorized user must have a clearance
key of proper security level in addition to an authenticated user
key and proper access privilege to retrieve the file key. As used
herein, a user key or a group key is a cipher key associated with
an authenticated user and may be used to access a secured file or
secure a file, or create a secured file. Additional detail on
obtaining such a user key upon a user being authenticated is
provided in U.S. patent application Ser. No. 10/074,194, which is
hereby incorporated herein by reference.
[0062] According to another embodiment, the security clearance
information 207 includes a set of special access rules to guard the
file key. The retrieval of the file key requires that the user pass
an access rule measurement. Since access privilege of a user may be
controlled via one or more system parameters (e.g., rules or
policies), the access rule measurement can determine if the user
has sufficient access privilege to retrieve the file key in
conjunction with the corresponding user key.
[0063] In accordance with the security clearance information 207, a
user may be assigned a hierarchical security clearance level based
on, perhaps, a level of trust assigned to the user. A level of
trust implies that one user may be more trusted than another and
hence the more trusted user may access more classified files.
Depending on implementation, a level of trust may be based on job
responsibility of the user or a role of the user in a project or an
organization background checks, psychological profiles, length of
service, etc. In any case, a level of trust assigned to the user
augments additional aspect to the access privilege of the user such
that the user must have proper security clearance to access a
classified secured file even if the user is permitted by the access
rules to access the file.
[0064] In general, a header is a file structure, preferably small
in size, and includes, or perhaps links to, security information
about a resultant secured document. Depending on implementation,
the security information can be entirely included in a header or
pointed to by a pointer that is included in the header. The
security information further includes the file key and/or one or
more clearance keys, in some cases, an off-line access permit
(e.g., in the access rules) should such access be requested by an
authorized user. The security information is then encrypted by a
cipher (i.e., an encryption/decryption scheme) with a user key
associated with an authorized user to produce encrypted security
information 210. The encrypted header 206, if no other information
is added thereto, is attached to or integrated with the encrypted
data portion 212 to generate the resultant secured file 208. In a
preferred embodiment, the header is placed at the beginning of the
encrypted document (data portion) to facilitate an early detection
of the secured nature of a secured file. One of the advantages of
such placement is to enable an access application (i.e., an
authoring or viewing tool) to immediately activate a document
securing module (to be described where it deems appropriate) to
decrypt the header if permitted. Nevertheless, there is no
restriction as to where the encrypted header 206 is integrated with
the encrypted data portion 212.
[0065] It is understood that a cipher may be implemented based on
one of many available encryption/decryption schemes. Encryption and
decryption generally require the use of some secret information,
referred to as a key. For some encryption mechanisms, the same key
is used for both encryption and decryption; for other mechanisms,
the keys used for encryption and decryption are different. In any
case, data can be encrypted with a key according to a predetermined
cipher (i.e., encryption/decryption) scheme. Examples of such
schemes may include, but not be limited to, Data Encryption
Standard algorithm (DES), Blowfish block cipher and Twofish cipher.
Therefore, the operations of the present invention are not limited
to a choice of those commonly-used encryption/decryption schemes.
Any cipher scheme that is effective and reliable may be used.
Hence, the details of a particular scheme are not further discussed
herein so as to avoid obscuring aspects of the present
invention.
[0066] In essence, the secured document 208 includes two parts, the
encrypted data portion 212 (i.e., encrypted version of the document
itself) and the header 210 that may point to or include encrypted
security information for the secured document 208. To access the
contents in the encrypted data portion 212, one needs to obtain the
file key to decrypt the encrypted data portion 212. To obtain the
file key, one needs to be authenticated to get a user or group key
and pass an access test in which at least the access rules in the
security information are measured against the user's access
privilege (i.e., access rights). If the secured file is classified,
it further requires a security level clearance on the user. In
general, the security clearance level of the user must be high
enough before the file key can be retrieved.
[0067] FIG. 2B illustrates an exemplary structure of a secured
document 220 including a header 222 and an encrypted portion 224.
The header 222 includes a security information block 226 having
encrypted security information that essentially controls the access
to the encrypted document 224. In a certain implementation, the
header 222 includes a flag 227 (e.g., a predetermined set of data)
to indicate that the document 220 is secured. The security
information block 226 includes one or more user IDs 228, access
rules 229, at least one file key 280 and other information 231. The
user IDs 228 maintain a list of authorized users who may be
measured against the access rules 229 before the file key 230 can
be retrieved. The access rules 229 determine at least who and how
the encrypted document 224 can be accessed. Depending on an
implementation, the other information 231 may be used to include
other information facilitating a secure access to the encrypted
document 224, the example may include version numbers or author
identifier.
[0068] In general, a document is encrypted with a cipher (e.g., a
symmetric or asymmetric encryption scheme). Encryption is the
transformation of data into a form that is impossible to read
without appropriate knowledge (e.g., a key). Its purpose is to
ensure privacy by keeping information hidden from anyone to whom it
is not intended, even those who have access to other encrypted
data. Decryption is the reverse of encryption. Encryption and
decryption generally require the use of some secret information,
referred to as a key. For some encryption mechanisms, the same key
is used for both encryption and decryption; for other mechanisms,
the keys used for encryption and decryption are different. For the
purpose of controlling the access to the document, the key or keys,
referred collectively to as a file key, may be the same or
different keys for encryption and decryption and are preferably
included in the security information (e.g., security information
block 226) contained in or pointed to by the header (header 222)
and, once obtained, can be used to decrypt the encrypted
document.
[0069] To ensure that the key is not to be retrieved or accessible
by anyone, the key itself is guarded by the access privileges and
rules. If a user requesting the document has the adequate access
privileges given the requirement of the access rules, the key will
be retrieved so as to permit the decryption of the encrypted
document.
[0070] To ensure that the security information or the header (if no
flag is implemented) is not readily revealed, the header itself can
be encrypted with a cipher. Depending on an exact implementation,
the cipher for the header may or may not be identical to the one
used for the document. The key (referred to as a user key) to
decrypt the encrypted header can, for example, be stored in a local
store of a terminal device (e.g., client computer) and activated
only when the user associated with it is authenticated. As a
result, only an authorized user can access the secured
document.
[0071] Optionally, the two encrypted portions (i.e., the encrypted
header and the encrypted document) can be encrypted again and only
decrypted by a user key. In another option, the encrypted portions
(either one or all) can be error checked by error checking portion
225, such as using a cyclical redundancy check to ensure that no
errors have been incurred to the encrypted portion(s) or the
secured document 220.
[0072] In general, each of the users in a security system is
assigned a user key or user keys (e.g., a user public key and a
private key). In some cases, the user key is also referred to as a
group key if a user is a member of group (e.g., Engineering) that
has uniform access privilege. In one application, the user public
key is used to encrypt some or all of the security information in
the header and the user private key is used to get into the
security information or header for the purpose of retrieving the
file or document key so as to decrypt the encrypted data portion or
the encrypted document. Unless specified otherwise, a user key
herein indicates either or both of the user public key and the
private key or a security key that is needed in the system to
retrieve the file key to decrypt the encrypted data portion.
[0073] In a typical enterprise environment, different users may
have different access privileges, some may access all secured files
while others may access some of the secured files with restricted
actions (i.e., printing, reading or editing, but not forwarding).
Whether a user can ultimately achieve the access to the encrypted
data portion in a secured file is controlled by the access rules or
additional key(s) in the security information of the header.
Limited by a user's access privilege, a user key associated with
the user may facilitate access to all secured files.
[0074] FIG. 3A illustrates a representative data structure of a
secured file 300 including a header 302 and an encrypted data
portion 304 according to one embodiment of the invention. The
secured file 300 is secured by access rules and use of encryption.
A user must possess a user key, a protection key, a file key and
sometimes a clearance key in order to access the secured file 300.
Depending on implementation, the header 302 may or may not include
a flag or signature 306. In one case, the signature 306 is used to
facilitate the detection of the security nature of a secured file
among other files. The header 302 includes a file key block 308, a
key block 310 and a rule block 312. The file key block 308 includes
a file key 309 that is encrypted by a cipher with a protection key
320 (i.e., a doc-key key sometimes) and further with a clearance
key 322 associated with a user that attempts to access the secured
file 300. Alternatively, the file key 309 is encrypted with the
clearance key 322 and then the protection key 320. The protection
key 320 is encrypted and stored in the key block 310. In general,
the key block 310 has an encrypted version of the protection key
320 and can be only accessible by designated user(s) or group(s).
There may be more than one key blocks 310 in a header, wherein
three key blocks are shown in FIG. 3A. To recover or retrieve the
protection key 320, a designated user must have proper access
privilege to pass an access rule test with the embedded access
rules in the rule block 312.
[0075] All access rules are encrypted with a user key (e.g., a
public user key) and stored in the rule block 312. A user
attempting to access the secured file uses must have a proper user
key (e.g., a private user key) to decrypt the access rules in the
rule block 312. The access rules are then applied to measure the
access privileges of the user. If the user is permitted to access
the secured file in view of the access rules, the protection key
320 in the key block 310 is retrieved to retrieve the file key 309
so as to access the encrypted data portion 304. However, when it is
detected that the secured file is classified, which means that the
file key can not be retrieved with only the protection key, the
user must posses a clearance key. Only the user that has the
clearance key and the retrieved protection key 320 is able to
retrieve the file key 309 and proceed with the decryption of the
encrypted data portion 304.
[0076] According to one embodiment, the encrypted data portion 304
is produced by encrypting a file that is non-secured. For example,
a non-secured document can be created by an authoring tool (e.g.,
Microsoft Word). The non-secured document is encrypted by a cipher
with the file key. The encryption information and the file key are
then stored in the security information, namely, the file key block
308 of the header 302.
[0077] According to another embodiment, the non-secured document
(data) is encrypted using the following aspects, a strong
encryption using a CBC mode, a fast random access to the encrypted
data, and an integrity check. To this end, the data is encrypted in
blocks. The size of each block may be a predetermined number or
specific to the document. For example, the predetermined number may
be a multiple of an actual encryption block size used in an
encryption scheme. One of the examples is a block cipher (i.e., a
type of symmetric-key encryption algorithm that transforms a
fixed-length block of plaintext (unencrypted text) data into a
block of ciphertext (encrypted text) data of the same length. This
transformation takes place under the action of a cipher key (i.e.,
a file key). Decryption is performed by applying the reverse
transformation to the ciphertext block using another cipher key or
the same cipher key used for encryption. The fixed length is called
the block size, such as 64 bits or 128. Each block is encrypted
using a CBC mode. A unique initiation vector (IV) is generated for
each block.
[0078] Other encryption of the non-secured data can be designed in
view of the description herein. In any case, the encryption
information and the file key are then stored in the security
information. One aspect of the present invention is that the
integration of a header and the encrypted data portion will not
alter the original meaning of the data that is otherwise not
secured. In other words, a designated application may still be
activated when a secured file is selected or "clicked". For
example, a document "xyz.doc", when selected, will activate an
authoring tool, e.g., Microsoft Word, commonly seen in a client
machine. After the document "xyz.doc" is secured in accordance with
the present invention, the resultant secured file is made to appear
the same, "xyz.doc" that still can activate the same authorizing
tool, except now the secured file must go through a process to
verify that a user is authenticated, the user has the proper access
privilege and (if imposed) sufficient security clearance.
[0079] Further, with the protection key, the file key can be
updated without having to modify the key-blocks. For example, with
respect to FIG. 3A, the file key 309 in the file key block 30 can
be updated without having to modify the key-blocks 310. One of the
features in the structure shown in FIG. 3A is that the underlying
mechanism facilitates the updating and management of the file
key.
[0080] In the above-described embodiment in FIG. 3A, the access
rules were encrypted with a user's public key. Those skilled in the
art can appreciate that the access rules can be encrypted in other
ways. For example, the access rules may be also encrypted with a
file encryption key (i.e., the file key) or the protection key. In
this case, the protection key is encrypted with a user's public key
or together with a clearance key associated with the user if a
subject secured file is secured. Alternatively, instead of
retrieving the protection key after the access rules are
successfully measured against access privilege of the user
attempting to access a secured file, the protection key can be
retrieved first with a user's private key. The protection key can
be used to retrieve the access rules that are subsequently used to
measure against the access privilege of the user if the protection
key was used to encrypt the access rules. If the user is permitted
to access the contents in the file, the file key is then retrieved
with the protection key (or together with the clearance key).
Alternatively, right after the protection key is retrieved, the
protection key (or together with the clearance key) is used to
retrieve the file key. The file key is then to retrieve the access
rules that are subsequently used to measure against the access
privilege of the user. In any case, if the user is determined have
sufficient access privilege in view of all access policies, if
there are any, the retrieved file key can be used to continue the
decryption of the encrypted data portion.
[0081] It should be noted that the header in a secured document may
be configured differently than noted above without departing from
the principles of the present invention. For example, a secured
document may include a header with a plurality of encrypted
headers, each can be accessible only by one designated user or a
group users. Alternatively, a header in a secured document may
include more than one set of security information or pointers
thereto, each set being for one designated user or a group of users
while a single file key can be used by all. Some or all of the
access rules may be viewed or updated by users who can access the
secured document.
[0082] In another alternative representative data structure for a
secured file, the header can include at least one pointer which
points to a remote data structure stored in a storage device. The
remote data structure can store some or all of the security
information, thereby shortening the size of the header and
improving manageability of security information. The storage device
is typically a local storage device. In other words, the
alternative data structure and the remote data structure are
typically stored on a common machine (e.g., desktop or portable
computer). The data structure stores security information.
Additional details on the alternative data structure can be found
in U.S. application Ser. No. 10/132,712 (Att. Dkt.:
SSL1P005/SS-14), filed Apr. 26, 2002, and entitled "METHOD AND
SYSTEM FOR PROVIDING MANAGEABILITY TO SECURITY INFORMATION FOR
SECURED ITEMS," which is hereby incorporated herein by
reference.
[0083] According to one embodiment, the access rules are present in
a descriptive language such as text or a markup language (e.g.,
HTML, SGML and XML). In a preferred embodiment, the markup language
is eXtensible Access Control Markup Language (XACML) that is
essentially an XML specification for expressing policies for
information access. In general, XACML can address fine-grained
control of authorized activities, the effect of characteristics of
the access requestor, the protocol over which the request is made,
authorization based on classes of activities, and content
introspection (i.e., authorization based on both the requestor and
attribute values within the target where the values of the
attributes may not be known to the policy writer). In addition,
XACML can suggest a policy authorization model to guide
implementers of the authorization mechanism.
[0084] In general, the data portion of a secured item is a document
or file encrypted with a cipher (e.g., a symmetric or asymmetric
encryption scheme). Encryption is the transformation of data into a
form that is impossible to read without appropriate knowledge
(e.g., a key). Its purpose is to ensure privacy by keeping
information hidden from anyone to whom it is not intended, even
those who have access to other encrypted data. Decryption is the
reverse of encryption. Encryption and decryption generally require
the use of some secret information, referred to as a key. For some
encryption mechanisms, the same key is used for both encryption and
decryption; for other mechanisms, the keys used for encryption and
decryption are different.
[0085] For the purpose of controlling the access to the document,
the key or keys, referred collectively to as a file key, may be the
same or different keys for encryption and decryption and are
preferably included in the security information contained in, or
pointed to by, the header and, once obtained, can be used to
decrypt the encrypted document. To ensure that the key is not to be
retrieved or accessible by anyone, the key itself is guarded by the
access privileges and rules. If a user requesting the document has
the proper access privileges that can be granted by the access
rules and system policies if there are any, the key will be
retrieved to proceed with the decryption of the encrypted
document.
[0086] To ensure that the security information or the header is not
readily revealed, at least a portion of the header itself can be
encrypted with a cipher. Depending on an exact implementation, the
cipher for the header may or may not be identical to the one used
for the document. The key (referred to as a user key) to decrypt
the encrypted header can, for example, be stored in a local store
of a terminal device and activated only when the user associated
with it is authenticated. As a result, only an authorized user can
access the secured document. In one embodiment, the key is
associated with a user's login to a local server or a central
server. Appropriate access privileges associated with the user can
then be validated if the user has been authenticated or previously
registered with the server and properly logged in. Optionally, the
two portions (i.e., the header (possibly encrypted) and the
encrypted document) can be encrypted again and only decrypted by a
user key. In another option, the encrypted portions (either one or
all) can be error-checked by an error-checking portion, such as
using a cyclical redundancy check to ensure that no errors have
been incurred to the encrypted portion(s) of the secured
document.
[0087] The security system according to the invention can, in
general, include or make use of one to many user computers and at
least one central server. The security system can also include or
make use of one or more local servers as desired. In other words,
the security systems operate in a distributed fashion.
[0088] Referring now to FIG. 3B, there is shown a functional block
diagram of a server device 320 in accordance with one embodiment of
the invention. The server device includes a server module 322 that
resides in a memory space 323 and is executable by one or more
processors 321. The server device 320 also includes a network
interface 324 to facilitate the communication between the server
320 and other devices on a network, and a local storage space 325.
The server module 322 is an executable version of one embodiment of
the present invention and delivers, when executed, features/results
contemplated in the present invention. According to one embodiment,
the server module 322 comprises an administration interface 326, an
account manager 328, a system parameter manager 330, a user monitor
332, a local server manager 334, a partner access manager 336, an
access report manager 338, and a rules manager 339.
[0089] Administration Interface 326:
[0090] As the name suggests, the administration interface 326
facilitates a system administrator to register users and grant
respective access privileges to the users and is an entry point to
the server module from which all sub-modules or the results thereof
can be initiated, updated and managed. In one embodiment, the
system administrator sets up hierarchy access levels for various
active folders, storage locations, users or group of users. The
privileges may include, but not be limited to: open, read, write,
print, copy, download and others Examples of the other privileges
are altering access privileges for other users, accessing secured
documents from one or more locations, and setting up a set of
access rules for a folder different from those previously set up
(perhaps by the system administrator). The respective user IDs
assigned to the users facilitate the management of all the users.
Unless specifically stated differently, a user or a corresponding
user ID is interchangeably used herein to identify a human user, a
software agent, or a group of users and/or software agents. Besides
a human user who needs to access a secured document, a software
application or agent sometimes needs to access the secured document
in order to proceed forward. Accordingly, unless specifically
stated, the "user" as used herein does not necessarily pertain to a
human being. In general, a user that will access a secured document
is associated with a user key to allow an encrypted header in a
secured document to be unlocked (decrypted). The expiration or
regeneration of a user key may be initiated by the system
administrator. According to one embodiment, the administration
interface 326 is a user graphic interface showing options for
various tasks that an authenticated system administrator or
operator may need to perform.
[0091] Account Manager 328:
[0092] Essentially, the account manager is a database or an
interface to a database 327 (e.g., an Oracle database) maintaining
all the registered users and their respective access privileges,
and perhaps corresponding user keys (e.g., private and public
keys). In operation, the account manager 328 authenticates a user
when the user logs onto the server 320 and also determines if the
user can access secured documents from the location the user's
current location.
[0093] System Parameters Manager 330:
[0094] This module is configured to manage system parameters within
the server module 322. These system parameters include, for
example, user access privileges, system rules, and one or more
keys. The system parameters manager 330 can be used to add, delete
or modify any of the system parameters. The system parameters
manager 330 can also interact with local modules and client modules
to supply the system parameters to these distributed modules. For
example, a user key can be expired (deleted) for security reasons
when a user leaves the organization or when its time to replace the
user key. As another example, a file key may be rotated on a
periodic or on-demand basis. The system parameters can be supplied
to local modules and client modules by a "push" of system
parameters to the other distributed modules or by a response to a
"pull" request for updated system parameters. Optionally, the
system parameters manager 330 may be further configured to act as a
key manager managing all keys used in the security system.
[0095] User Monitor 332:
[0096] This module is configured to monitor user's requests and
whereabouts. Typically, a user is granted to access secured
documents from one or more designated locations or networked
computers. If a user has a higher access privilege (e.g., to permit
access from other than the locations or networked computers), the
user monitor 332 may be configured to ensure that the user can have
only one access from one of the registered locations or computers
at all times. In addition, the user monitor 332 may be configured
and scheduled to interact with the system parameters manager 330 to
"push" an update of system parameters or respond to a "pull"
request for an update of system parameters.
[0097] Local Server Manager 334:
[0098] This module is designed to be responsible for distributing
an appropriate local module for a local server servicing a
predetermined location or a predetermined group of users. According
to one embodiment, the local server manager 334 replicates some or
all of the server module 322 being executed on the server 320 and
distributes the replicated copy to all the local servers. As a
result, a user can access secured documents anywhere within the
network premises covered by the local servers without being
authenticated at a single central server, namely the server 320.
According to another embodiment, the local server manager 334
replicates some of the server module 322 being executed on the
server 320 and distributes the replicated copy to a corresponding
local server, in this embodiment, each of the local servers will
have its own customized replication from the server module 322.
[0099] Partners Access Manager 336:
[0100] A special module to manage non-employees accounts. The
non-employees may be consultants to a business that requires the
consultants to access certain secured documents. The partners
access manager 336 generally works in accordance with other modules
in the server but puts additional restrictions on such users being
directly managed by the partners access manager 336. In one
application, the partners access manager 336 generates a request to
the user key manager 330 to expire a key or key pair for a
consultant when an engagement with the consultant ends.
[0101] Access Report Manager 338:
[0102] A module is configured to record or track possible access
activities and primarily works with a corresponding sub-module in a
client module being executed in a client machine. The access report
manager 338 is preferably activated by the system administrator and
the contents gathered in the access report manager 338 and is
typically only accessible by the system administrator.
[0103] Rules Manager 339:
[0104] In general, the rules manager 339 is an enforcement
mechanism of various access rules. According to one aspect, the
rules manager 339 is configured to specify rules based on i) data
types (e.g., Microsoft Word), ii) group users or individual, iii)
applicable rights, and iv) duration of access rules. Typically, a
set of rules is a policy (namely, a security policy). A policy can
be enabled, disabled, edited, deployed and undone (e.g., one or two
levels). Policies managed by the rules manager 339 operate
preferably on a global level. The rules (as well as other system
parameters) are typically downloaded to the client machine during
the login process (after the user is authenticated) and can be
updated dynamically. In addition, respective policies may be
associated with active folders (i.e., those designated places to
store secured documents). These polices are also downloaded and
updated on the client machine. Simple policies can also be embedded
in the document and provide document specific policies.
[0105] According to one embodiment, a header is received by a local
server from a client and the access rules from the header are
retrieved. The key manager 330 can be called upon to decrypt the
encrypted security information in the header. The rules manager 339
can then parse the access rules from the security information and
evaluate or measure the access rules against the access privileges
of the user to determine whether the secured document can be
accessed by the user. If the evaluation or measurement succeeds, a
file key is retrieved and sent back to the client.
[0106] It should be pointed out that the server module 322 in FIG.
3B lists some exemplary modules according to one embodiment of the
present invention and not every module in the server module 322 has
to be implemented in order to practice the present invention. Those
skilled in the art can understand that given the description
herein, various combinations of the modules as well as
modifications thereof without departing the spirits of the present
invention, may achieve various desired functions, benefits and
advantages contemplated in the present invention.
[0107] FIG. 3C shows a functional block diagram of a local server
device 340 according to one embodiment of the invention. The local
server device 340 executes a module, referred herein as a local
module 342 which is configured to be a complete or partial
replication of the server module 322 of FIG. 3B. The local server
device 340 is generally similar to that of a server as illustrated
in FIG. 3B. Namely, the local server device 340 includes one or
more processors 341, a memory space 343, a network interface 344,
and a local storage space 345. Given the similarity, many parts
illustrated in FIG. 3C are not to be described again to avoid
obscuring aspects of the present invention. The local module 342
provides the dependability, reliability and scalability of the
centralized access control management being undertaken by the
central server 320 of FIG. 3B. As such, not all authentication
requests need to be handled at one central point without losing
control of the access control management. The users are thus not
affected if the central server is brought down for maintenance and
the connection to the central server is not available. If a number
of local servers are used and each has a replication of the server
module, the reliability of servicing the users is greatly enhanced.
As a result, the local users need only to check with the
corresponding local server and none of the users would be affected
if other local servers are down for whatever reasons or
disconnected from the central server.
[0108] The configuration of a user's access to secured documents is
sometimes referred to as a provisioning process. The dynamic
provisioning that has been deserted above is believed to provide
the necessary security means needed by a large enterprise having
employees in several locations without the loss of the centralized
access control management at a central server. Further, the use of
multiple local servers to support the central server can provide
increased dependability, reliability and sociability.
[0109] Referring now to FIG. 3D, there is shown a functional block
diagram of a client machine 360 according to one embodiment of the
invention. As used herein, the client machine 360 is a computing
device primarily used by a user to access secured documents. The
client machine 360 can, for example, be a desktop computer, a
mobile device or a laptop computer. According to one embodiment,
the client machine 360 includes a processor 361, a client module
362, a memory space 363, a network interface 365 and a local store
367. The client module 362 resides in the memory space 363 and,
when executed by the processor 361, delivers features, advantages
and benefits contemplated in the present invention. Through the
network interface 365, the client machine 360 is capable of
communicating over a data network with other computers, such as a
server. From the client machine 360, a user can access secured
documents located in a repository (store) 366 that may be in the
client machine 360, another networked device, or other storage
means. According to one embodiment, the client module 362 includes
a number of sub-modules including an access report module 364, a
user verifying module 370, a key manager 368, a document securing
module 371 and an off-line access manager 374.
[0110] Access Report Module 364:
[0111] This module is a software agent configured to record access
activity and associated with an authenticated user. It reports to
an access report module in the central server so that a record may
be established as to what secured document has been accessed by
which user during what time. In particular, the access report
module 364 can be activated to capture access activities of the
user when the client machine is not networked. The access
activities will be later synchronized with the counterpart in the
server to facilitate the access control management for the offline
access.
[0112] Key Manager 368:
[0113] One of the purposes for the key manager 368 is to ensure
that a secured document is still usable when the secured document
is being accessed by an application that suddenly crashes.
According to one embodiment, after the encrypted header is
decrypted, the file key is then copied or a copy thereof is stored
(cached) into the key manager 368. The file key is then used to
decrypt the encrypted document. A clear document is now available
to the application. If the application crashes due to power outage
or interfered by another application or OS, the file key in the
header could be damaged. If no copy of the file key is available,
the secured document may not be usable any more because the
encrypted document would not be decrypted without the file key. In
this case, the reserved key maintained in the key manager 368 can
be used to replace the damaged key and decrypt the encrypted
document. After the user saves the file again, the file key is put
back into the header. Another purpose for the key manager 368 is to
cache a user key or keys of an authenticated user.
[0114] User Verifying Module 370:
[0115] This module is responsible for determining if a user
accessing a secured document has been authenticated otherwise it
will initiate a request for authentication with a local server or a
central server. In other words, the user verifying module 370 is
always consulted before a permission is granted to the user seeking
access to a secured document. According to one embodiment, a user
key or keys of an authenticated user are stored (cached) in the key
manager 368 once the user is authenticated by the user verifying
module 370 via the server. When a secured document is accessed, the
user key must be retrieved from the key manager 368 to decrypt the
encrypted security information in the header of the secured
document.
[0116] Document Securing Module 371:
[0117] As described above, the DSM 371 includes a cipher 372 that
is used to generate a file/user key and encrypt/decrypt a
document/header. In addition, other securing means may be
implemented in the DSM 371, for example, a filter to block copying
contents in a secured document into a non-secured document or a
link from a secured document/original source to another document or
recipient source.
[0118] Off-Line Access Manager 374:
[0119] This module becomes effective only when the networked client
machine is off the network, namely, the communication with a local
server or a central server is not currently available. For example,
a user is on the road and still needs to access some secured
documents in a laptop computer. When five consultation is not
available, the off-line access manager 374 is activated to ensure
that the authorized user still can access the secured document but
only for a limited time and perhaps with a limited privilege.
[0120] It should be pointed out that the client module 362 in FIG.
3D lists some exemplary sub-modules according to one embodiment of
the present invention and not every module in the server module 362
has to be implemented in order to practice the present invention.
Those skilled in the art can understand that given the description
herein, various combinations of the sub-modules, may achieve
certain functions, benefits and advantages contemplated in the
present invention.
[0121] According to one aspect of the invention, keys that are used
to secure files can use arbitrary strings. Such keys are preferably
public keys (also known as identity based public keys) that are
used to encrypt files (or documents). Specifically, the public keys
are arbitrary strings that embed or encode access restrictions (or
access rules). The access restrictions are used to enforce access
control policies. Counterpart private keys are used to decrypt the
files that have been previously encrypted with the public keys. The
private keys can be generated to decrypt the portions of the files
that have previously been encrypted with the public keys.
[0122] Because the public keys are based on arbitrary strings, the
public keys and their private key counterparts are able to be
generated in a decentralized manner (as well as in a centralized
manner). The ability to generate keys in a decentralized manner
substantially eliminates key distribution burdens and facilitates
off-line access to encrypted files. In the embodiments discussed
below, the public keys which are based on arbitrary strings are
preferably used as file keys to secure files. Often, the file keys
are symmetric keys. However, in other embodiments, arbitrary
strings can be used with other public keys besides file keys. Such
other public keys might, for example, be associated with user keys
(also known as a group key when the key pertains to a group of
users), clearance keys, or protection keys.
[0123] FIG. 4 is a block diagram of a file security system 400
according to one embodiment of the invention. The file security
system 400 includes an access server 402 and client machines 404
and 406. The access server 402 can pertain to a local server or a
central server as noted above with respect to FIGS. 1A-1C. The
access server 402 couples to a network 408, and the client machines
404 and 406 also couple to the network 408. The network 408, for
example, can pertain to one or more of the Internet, a wide area
network, a local area network, etc.
[0124] The access server 402 includes an access manager 410 and a
key generator 412 with a rules engine. The access manager 410
provides centralized control for management of user access to
secured files. The secured files can be associated with the access
server, such as stored in a file store 414, or associated with
client machines 404 and 406 and stored in file stores such as a
file store 416 or a file store 418. The access manager 410
communicates with the key generator 412 to decide whether a
particular user is granted access to a secure file. In this regard,
the key generator 412 within the rules engine evaluates the rules
(e.g., access rules) that are associated with the secure file to be
accessed. If the rules engine 412 determines that the access
requested is permissible, then the key generator 412 generates a
key that can be utilized in gaining access to the secure file. The
generated key is supplied to the access manager 410. The access
manager 410 can either gain access to the secured file using the
generated key or can supply the generated key to the appropriate
client machine which in turn gains access to the secured file using
the generated key. In one embodiment, the generated key can be
referred to as a file key.
[0125] FIG. 5 is a block diagram of a distributed file security
system 500 according to one embodiment of the invention. The
distributed file security system 500 distributes security
operations to local client machines to distribute processing load
as well as to reduce key transfer and distribution across
networks.
[0126] The distributed file security system 500 includes an access
server 502 and a representative client machine 504 coupled through
a network 506. The access server 502 includes at least an access
manager 508 that controls access to secure files managed by the
distributed file security system 500. The client machine 504
couples to a file store 510 where secured files are stored. In
addition, the client machine 504 couples to a hardware (HW) card
512 (e.g., a smart card). The hardware card 512 is, more generally,
a peripheral device coupled to the client machine 504. As
illustrated in FIG. 5, the hardware card 512 includes an access
controller 514, a key generator with rules engine 516 and a key
store 518.
[0127] When a user of the client machine 504 desires to access a
secured file that is managed by the distributed file security
system 500, the user of the client machine 504 is typically first
authenticated by the access manager 508 of the access server 502.
Then, a rules string associated with access rules is used as a key
(namely, public key) to access the secured file. The key generator
with rules engine 516 within the hardware card 512 receives the
rule string and evaluates whether the user has sufficient
privileges to access the secured file in view of the rules embedded
within the rules string. When the key generator with rules engine
516 determines that the user is permitted access to the secured
file, the access controller 514 produces a private key which is
used to decrypt the secured file. The private key can also be
stored to the key store 518. In this embodiment, the private key
preferably resides within the hardware card 512 and thus is not
transmitted beyond the hardware card 512. In other words, the
private key is not stored on the client machine 504, nor does the
client key traverse the network 806 to be stored in the access
server 502.
[0128] FIG. 6 is a flow diagram of access rules based encryption
processing 600 according to one embodiment of the invention. The
access rules based encryption processing 600 is, for example,
performed by the access server 402 illustrated in FIG. 4. The
access server 402 can represent a central server or a local server
of a security system. The access server 402 can also represent the
server device 104, 106 illustrated in FIGS. 1A and 1B. Some or all
of the access rules based encryption processing 600 can be
performed at the client machines 404, 406 of FIG. 4 or the client
machines of FIGS. 1A-1C.
[0129] The access rules based encryption processing 600 initially
obtains 602 access rules to be imposed. Namely, the access rules to
be imposed are those access rules that are to be applied in
securing a file. Next, a rules string is produced 604 in accordance
with the access rules.
[0130] The rules string can follow a predetermined format to embed
the access rules. Although the rules string can vary, one example
of a rules string is "9:00 am to 5:00 pm<Dec. 31, 2002" which
encodes access rules that indicate that access to the associated
secured file is only permitted between 9:00 am and 5:00 pm but only
prior to Dec. 31, 2002. Another example is "10:00 am-2:00 pm on
machine 10.200.255.213" which encodes access rules that indicate
that access to the associated secured file is only permitted
between 10:00 am and 2:00 pm from a machine having a specific
network address. The rules string can also include an access rule
that limits access to the secured file to certain groups of users.
For example, a group "human resources" could be used in an access
rule to limit access to personnel files to only those users that
are deemed in the human resources group. Still another example is
"Engineering, 9:00 am and 5:00 pm, Mon-Fri, off-line, MS-Word"
which encodes access rules that indicate that access to the
associated secured file is only permitted by user of the
Engineering group, between 9:00 am to 5:00 pm, Monday through
Friday, when off-line and when using MS-Word.
[0131] Once the rules string has been produced 604, a public key is
generated 606 based on the rules string. Here, the securing of the
file is simplified in that the public key is derived from the rules
string which in turn includes the access rules. In other words, the
public key is generated based on the rules string. Consequently,
the public key is thus not supplied by a key generator (which would
require distribution public/private key pairs). Thereafter, at
least a portion of the file is encrypted 608 using the public key.
In one embodiment, the portion of the file being encrypted 608 is a
data portion of the file. Once the portion of the file is encrypted
608, the access rules based encryption processing 600 is complete
and ends.
[0132] FIG. 7 is a flow diagram of access rules based decryption
processing 700 according to one embodiment of the invention. The
access rules based decryption processing 700 is performed in order
to decrypt a file that has been previously encrypted (i.e., secured
file).
[0133] According to the access rules based decryption processing
700, a public key string associated with the secured file is
obtained 702. Next, access rules associated with the public key are
identified 704. In one embodiment, the access rules can be embedded
in the public key string. The access rules are then evaluated 706.
A decision 708 then determines whether the access rules are
satisfied. Here, the access rules can be compared against access
privileges associated with the requestor that desires access to the
secured file. These access rules are not only used to formulate a
public key, but also used to determine whether the requestor has
sufficient privileges and rights to satisfy the access rules and
thus gain access to the secured file.
[0134] When the decision 708 determines that the access rules are
not satisfied, then access to the secured file is denied 710. On
the other hand, when the decision 708 determines that the access
rules are satisfied, then a private key is generated 712 based on
the access rules and a master key. In one embodiment, the private
key can be referred to as a file key. After the private key has
been generated 712, at least a portion of the secured file is
decrypted 714 using the private key. In one embodiment, the portion
of the secured file being decrypted 714 is a data portion of the
secured file. Following the operation 714, as well as following the
operation 710, the access rules based decryption processing 700 is
complete and ends.
[0135] As used herein, a master key is used to generate a private
key. Hence, access to the master key must be restricted. In one
embodiment, the master key is generated or regenerated based on
gathered information. In the context of the present invention, the
gathered information which may be considered a seed to generate a
master key or the master key may itself be distributed among a
central server, one or more local servers, and a local device
(e.g., a smart card or simply a local client machine). In other
words, generation the master key or acquisition of the master key
is shared among different machines, none could act alone to obtain
the master key to proceed with the processes described herein. In
one embodiment, a segment of the information is stored in the
central server, another segment of the information is stored in a
local server and a third segment of the information is stored in
the local device. Only under the condition that the user is
authenticated by the server (the central or local server), can the
distributed segments of the information be gathered together to
generate the master key or recover the master key. Further, the
recovered or generated master key can, for example, also be
configured to be valid for a certain period of time or for a fixed
number of uses to enhance the security thereof.
[0136] FIG. 8 is a flow diagram of access rules based encryption
processing 800 according to another embodiment of the invention.
The access rules based encryption 800 is, for example, performed by
a distributed file security system, such as the distributed file
security system 500 illustrated in FIG. 5.
[0137] The access rules based encryption processing 800 initially
obtains 802 access rules to be imposed when securing a file. Next,
a rule string is produced 804 in accordance with the access rules.
As noted above with respect to FIG. 6, the rules string can follow
a predetermined format to embed the access rules. A key block of
the file to be encrypted (or secured) can then be obtained 806. In
one embodiment, a key block is a part of a header of a file format
that includes one or more keys that are used to decrypt data within
a data portion of the file format.
[0138] A public key for the key block is generated 808 based on the
rule string. Here, the public key is able to be relatively easily
generated given that it is based on the rules string. In other
words, the public key can be generated without requiring the
generation of a private/'key pair and without the need to
distribute of such keys. After the public key for the key block has
been generated 808, the key block of the file is then encrypted 810
using the public key. The encrypted key block is then returned 812
to the requesting device. The encrypted key block is then able to
be affixed to the encrypted data portion of the secured file. For
example, the encrypted key block can form part of the security
information of the header portion of the secured file. In one
embodiment, the data portion was previously encrypted using the one
or more keys within the key block.
[0139] FIG. 9 is a flow diagram of access rules based decryption
900 according to one embodiment of the invention. The access rules
based decryption processing 900 is, for example, performed by a
combination of an access server and a hardware card associated with
a distributed data security system.
[0140] The access rules based decryption processing 900 initially
obtains 902 a public key string associated with a secured file.
Then, access rules associated with the public key are identified
904. An encrypted key block is also obtained 906. After the access
rules have been identified 904, the access rules within the public
key are evaluated 908. A decision 910 determines whether the access
rules are satisfied. When the decision 910 determines that the
access rules are satisfied, then a private key is generated 912
based on the access rules and a master key. Then, the encrypted key
block is decrypted 914 to acquire a file key. Thereafter, the file
key is utilized to decrypt 916 at least a portion of the secured
file using the file key. In one embodiment, the at least the
portion of the secured file pertains to a data portion of the
secured file.
[0141] On the other hand, when the decision 910 determines that the
access rules are not satisfied, then access to the secured file is
denied 918. Additionally, after access to the secured file has been
denied 918, additional processing can be performed to restrict
unauthorized users from making additional requests to access
secured files. For example, a decision 920 can determine whether to
"lock down" the file security system to prevent further access to
storage resources that store important security keys. When the
decision 920 determines that a lock down should be performed, then
subsequent access to the secured file, and perhaps other secured
files maintained or managed by the same hardware card, are
prevented 922. In other words, once the secured file, or the
hardware card storing the secured filed, is locked down, the
secured file is not able to be being subsequently accessed 922.
Following the operations 916 and 922, as well as following the
decision 920 when a lock down should not be performed, the access
rules based decryption processing 900 is complete and ends.
[0142] In one embodiment, the operations 908 through 914 are
performed internal to a tamper proof device, such as a hardware
card (e.g., the hardware card 512 of FIG. 5). As a result, the
master key and a key generation algorithm can be stored in the
hardware card in a secure manner. The private key being generated
can also remain internal to the hardware card. In another
embodiment, the master key can have one part (or segment) within
the tamper proof device and another part (or segment) on a server
or client machine. In such an embodiment, a secure communication
cannel can be used for communications between the various
devices.
[0143] The results of the access rules based decryption 700, 900
can be considered a clear file (i.e., decrypted file or decrypted
data portion). The clear file refers to the fact that the
previously secured file is no longer secured, and is thus usable.
The clear file can be returned to the requestor. Nevertheless, the
processing described above with respect to the access rules based
decryption processing 700, 900 shown in FIGS. 7 and 9 is typically
preceded by authorization processing. Authorization processing
operates to authenticate the user seeking access to a secured
file.
[0144] FIG. 10 illustrates flow diagrams of an authorization
process 1000 according to one embodiment of the invention. The
authorization process 1000 begins with a decision 1002 that
determines whether a request to access a secured file has been
received. When the decision 1002 determines that such a request has
not yet been received, the authorization process 1000 waits for
such a request. In other words, the authorization process 1000 can
be considered to be invoked when a request to access a secured file
is received.
[0145] Once the decision 1002 determines that a request to access a
secured file has been received, a decision 1004 determines whether
the user and/or the client machine have been authenticated.
Typically, the request is initiated by a user of a client machine.
For security, both the user and the client machine are
authenticated. When the decision 1004 determines that both the user
and the client machine have not yet been authenticated, then
authentication processing is performed 1006. The authentication
processing that is performed 1006 serves to not only authenticate
that the user is who the user claims he or she is, but also to
determine that the client machine that the user is utilizing is one
authorized to be used by the user. In the event that authentication
were to be unsuccessful, the authorization process 1000 would end
and the user would be unable to access the secured file. Additional
details on authentication processing are provided below with
reference to FIG. 11.
[0146] On the other hand, when the decision 1002 determines that
the user and the client machine have already been authenticated, as
well as after the authentication processing has been performed
1006, a user key associated with the user is retrieved 1008. The
user key can be retrieved 1008 from a storage location that is
local or remote with respect to the computing device performing the
authorization process 1000. After the user key has been retrieved
1008, part or all of the security information in the header portion
of the secured file can be decrypted 1010 using the user key. As
noted above, the secured file includes a header and a data portion.
The header can include, among other things, security information.
One component of the security information for the secured file is a
file key. The file key can be used to decrypt the data portion of
the secured file. Hence, after the security information in the
header is decrypted 1010 using the user key, the authorization
processing 1000 is complete and ends.
[0147] FIG. 11 shows a flowchart of a user authentication process
1100 that may be implemented in a server, such as an access server,
a central server or a local server. As described above, there are
at least two situations that will call upon the user authentication
process 1100--initial login to a networked client machine and first
access to a secured document. When either of these situations
happens, a client module in the client machine initiates a request
that is transmitted to a server running a module providing the
access control management to start the user authentication process
1100.
[0148] At a decision 1102, the server awaits a request (e.g.,
authentication request) from the client machine. Upon receiving the
request from the client machine, the server proceeds at a decision
1104 to determine if the user and the client machine from which the
user attempts to access a secured document have already been
authenticated. If both have already been authenticated, processing
skips to operation 1112. On the other hand, the authentication
processing 1100 continues when the decision 1104 determines that
the user and the client machine have not already been
authenticated. In one embodiment, the server may initiate a secured
link with the client machine if both the server and the client
machine are coupled to an open network, such link may be over HTTPS
or supported through VPN. Alternatively, there may be a direct link
between the client and the server if another authentication means
is employed.
[0149] Next, the server responds 1106 to the received request with
an authentication response. Depending on implementation, such
response may be a dialog box to be displayed on the screen of the
client machine, a command or other demand. In any case, the
response requires that credential information be provided by the
user. As described before, the credential information may be a set
of username and password or biometric information of the user and
must be received from the user. A decision 1108 then causes the
authentication processing 1100 to await for such credential
information before the authentication processing 1100 may proceed.
Upon receiving the credential information, a decision 1110
determines whether the user is authenticated. Here, the decision
1110 can determines whether the user is authenticated to access any
secured files. If the decision 1110 determine that the user is not
authenticated, the authentication processing 1110 goes back to the
beginning of the authentication processing 1100 to continue waiting
for a request. In other words, the current request to access the
secured documents or login to the system is abandoned. If the
decision 1110 determines that the user is authenticated, the user
is then recognized as being authentic. At the same time, the client
machine can undergo a similar authentication by, perhaps, an IP
address thereof, or a network card identification therein, or other
means that uniquely identifies the client machine.
[0150] After authentication of both the user and the client
machine, the user's access privilege is activated 1112. Depending
on implementation, an activation of the user's access privilege may
be a downloading of a file containing the access privilege to the
client machine, a decryption of a local file containing the access
privilege, or simply an activation of the user in a memory space of
the server. In any case, at this point, the user's access
privilege(s) is readily accessible, thus permitting the user to
access the secured documents from the authenticated client
machine.
[0151] As described above, according to one embodiment, the secured
document includes two encrypted portions, the header with encrypted
security information and the encrypted data portion (i.e., the
encrypted document). The two parts in the secured document are
encrypted respectively with two different keys, the file key and
the user key. Alternatively, the two encrypted portions may be
encrypted again with another key (or use the same user key).
[0152] The invention also facilitates sharing secured files between
different organizations. Here, in one embodiment, a unique company
identifier can be encoded into the rules string and thus become
part of the public key of the company. Upon receiving a secured
file, a user key (a private key) of the company can be generated
locally to access the secured file.
[0153] In the case that there are a number of sets of access rules,
each for a particular user or a group of users, it can be
understood that the encrypted access rules can be integrated with
other sets of the encrypted access rules in a rules block as
illustrated in FIG. 3A. As such, access from one user or group will
not affect other users or groups but the other users or groups will
see perhaps an updated version of the encrypted document.
[0154] The invention is preferably implemented by software or a
combination of hardware and software, but can also be implemented
in hardware. The invention can also be embodied as computer
readable code on a computer readable medium. The computer readable
medium is any data storage device that can store data which can
thereafter be read by a computer system. Examples of the computer
readable medium include read-only memory, random-access memory,
CD-ROMs, DVDs, magnetic tape, optical data storage devices, and
carrier waves. The computer readable medium can also be distributed
over network-coupled computer systems so that the computer readable
code is stored and executed in a distributed fashion.
[0155] The various embodiments, implementations and features of the
invention noted above can be combined in various ways or used
separately. Those skilled in the art will understand from the
description that the invention can be equally applied to or used in
other various different settings with respect to various
combinations, embodiments, implementations or features provided in
the description herein.
[0156] The advantages of the invention are numerous. Different
embodiments or implementations may yield one or more of the
following advantages. One advantage of the invention is that public
keys used to encrypt files are not generated prior to protection.
Consequently, the system does not need to generate keys in advance
and then store and distribute them. Another advantage of the
invention is that the public keys encode rules that provide access
restrictions. The rules (access rules) are also used to generate
the private keys, which protects the rules from being modified.
Still another advantage of the invention is that off-line access to
protected (secured) documents is facilitated. Yet still another
advantage of the invention is that protected files are able to be
easily shared between groups within a particular organization as
well as between disparate organizations.
[0157] The foregoing description of embodiments is illustrative of
various aspects/embodiments of the present invention. Various
modifications to the present invention can be made to the preferred
embodiments by those skilled in the art without departing from the
true spirit and scope of the invention as defined by the appended
claims. Accordingly, the scope of the present invention is defined
by the appended claims rather than the foregoing description of
embodiments.
* * * * *