U.S. patent application number 09/115422 was filed with the patent office on 2001-12-13 for encryption system with time-dependent decryption.
Invention is credited to KAWAZOE, HIROSHI, KUDO, MICHIHARU, NUMAO, MASAYUKI.
Application Number | 20010052071 09/115422 |
Document ID | / |
Family ID | 26527400 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010052071 |
Kind Code |
A1 |
KUDO, MICHIHARU ; et
al. |
December 13, 2001 |
ENCRYPTION SYSTEM WITH TIME-DEPENDENT DECRYPTION
Abstract
An object of the invention is to provide an encryption system
and method for inhibiting the decryption of encrypted data unless a
decryption condition is satisfied. Thus, according to the present
invention, in order to provide the encryption system for inhibiting
the decryption of encrypted data unless a decryption condition is
satisfied, decryption enabled time is designated as a decryption
condition, and an encryption system incorporating time-dependent
decryption is constituted by a time-key certificate and a time-key
certificate manager. A time-key certificate is employed when a
third party proves that a public encryption key added to the
certificate satisfies the decryption condition. The time-key
certificate manager issues a time-key certificate and then manages
a decryption key.
Inventors: |
KUDO, MICHIHARU;
(KAMAKURA-SHI, JP) ; NUMAO, MASAYUKI;
(KAWASAKI-SHI, JP) ; KAWAZOE, HIROSHI;
(YOKOHAMA-SHI, JP) |
Correspondence
Address: |
LOUIS P HERZBERG
IBM CORPORATION
P O BOX 218
YORKTOWN HEIGHTS
NY
10598
|
Family ID: |
26527400 |
Appl. No.: |
09/115422 |
Filed: |
July 14, 1998 |
Current U.S.
Class: |
713/156 ;
713/178 |
Current CPC
Class: |
H04L 9/321 20130101;
H04L 9/3297 20130101; H04L 9/3263 20130101 |
Class at
Publication: |
713/156 ;
713/178 |
International
Class: |
H04L 009/30 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 22, 1997 |
JP |
9-226903 |
Nov 25, 1997 |
JP |
9-322825 |
Claims
What is claimed is:
1. An encryption system with time-dependent decryption, including a
time-key manager for guaranteeing that a time for enabling
decryption of information is limited, (1) wherein, upon receipt of
a request from an information server, said time-key manager
transmits to said information server a time-key certificate
including disclosure time information and a public key for
encryption; and (2) wherein said information server transmits to an
information user information encrypted using said public key, which
is included in said time-key certificate, and said time-key
manager, following the receipt of a request for a decryption key
from said information user, transmits said decryption key to said
information user at such time said disclosure time has been
reached.
2. A time-key manager for guaranteeing that a time for enabling
decryption of information is limited, comprising: (1) means for,
upon receipt of a request from an information server, transmitting
to said information user a time-key certificate including
disclosure time information and a public key for encryption; and
(2) means for, after said information server transmits to an
information user information encrypted using said public key, which
is included in said time-key certificate, receiving a request for a
decryption key from said information user and transmitting said
decryption key to said information user at such time said
disclosure time has been reached.
3. A disclosure time designation file transfer system, which
includes a time-key manager for guaranteeing that a time for
enabling decryption of an encrypted file is limited, (1) wherein,
upon receipt of a request from an information server, said time-key
manager transmits to said information server a time-key certificate
including disclosure time information and a public key for
encryption; and (2) wherein said information server transmits to an
information user said file encrypted using said public key, which
is included in said time-key certificate, and said time-key
manager, following the receipt of a request for a decryption key
from said information user, transmits said decryption key to said
information user at such time said disclosure time has been
reached.
4. An electronic tendering system, which includes a time-key
manager for guaranteeing that a time for enabling decryption of
tender information is limited, (1) wherein, upon receipt of a
request from an order receiver, said time-key manager transmits to
said order receiver a time-key certificate including disclosure
time information and a public key for encryption; and (2) wherein
said order receiver transmits to an order submitter said tender
information encrypted using said public key, which is included in
said time-key certificate, and said time-key manager, following the
receipt of a request for a decryption key from said order
submitter, transmits said decryption key to said order submitter at
such time said disclosure time has been reached.
5. An electronic tendering system, which includes a time-key
manager, for guaranteeing that a time for enabling decryption of
tender information is limited, and a tender manager for
transmitting messages exchanged by an order receiver and an order
submitter, (1) wherein, upon receipt of a request from an order
receiver, said tender manager acquires from said time-key manager a
time-key certificate, which includes disclosure time information
and a public key for encryption, and transmits said time-key
certificate to said order receiver; (2) wherein said tender manager
receives tender information that said order receiver has encrypted
using said public key included in said time-key certificate; and
(3) wherein, upon receipt of a request from said order submitter,
said tender manager acquires a decryption key from said time-key
manager after said disclosure time has been reached, and transmits
said decryption key to said order submitter.
6. The system according to claim 4 or 5, wherein said public key
and a secret key differ depending on tender types.
7. A tender manager for guaranteeing that a time for enabling
decryption of tender information is limited, comprising: (1) means
for, upon receipt of a request from an order receiver, acquiring
from said time-key manager a time-key certificate, which includes
disclosure time information and a public key for encryption, and
for transmitting said time-key certificate to said order receiver;
(2) means for receiving tender information that said order receiver
has encrypted using said public key included in said time-key
certificate; and (3) means for, upon receipt of a request from said
order submitter, acquiring a decryption key from said time-key
manager after said disclosure time has been reached, and
transmitting said decryption key to said order submitter.
8. An electronic safe system, which includes a time-key manager for
guaranteeing that a time for enabling decryption of electronic
money information is limited, (1) wherein, upon receipt of a
request from a depositor, said time-key manager transmits to said
depositor a time-key certificate including disclosure time
information and a public key for encryption; and (2) wherein said
depositor transmits to a bank said electronic money information
encrypted using said public key, which is included in said time-key
certificate, and said time-key manager, following the receipt of a
request for a decryption key from said bank, transmits said
decryption key to said bank after said disclosure time has been
reached.
9. An electronic safe system, which includes a time-key manager for
guaranteeing that a time for enabling decryption of electronic
money information is limited, and an electronic money manager for
transmitting messages exchanged by a depositor and a bank, (1)
wherein, upon receipt of a request from a depositor, said
electronic money manager acquires from said time-key manager a
time-key certificate, which includes disclosure time information
and a public key for encryption, and transmits said time-key
certificate to said depositor; (2) wherein said electronic money
manager receives electronic money information that said depositor
has encrypted using said public key included in said time-key
certificate; and (3) wherein, upon receipt of a request from said
bank, said electronic money manager acquires a decryption key from
said time-key manager after said disclosure time has been reached,
and transmits said decryption key to said bank.
10. The system according to claim 8 or 9, wherein said public key
and a secret key differ depending on electronic money types.
11. An electronic money manager for guaranteeing that a time for
enabling decryption of electronic money information is limited,
comprising: (1) means for, upon receipt of a request from a
depositor, acquiring from said time-key manager a time-key
certificate, which includes disclosure time information and a
public key for encryption, and for transmitting said time-key
certificate to said depositor; (2) means for receiving electronic
money information that said depositor has encrypted using said
public key included in said lime-key certificate; and (3) means
for, upon receipt of a request from said bank, acquiring a
decryption key from said time-key manager after said disclosure
time has been reached, and for transmitting said decryption key to
said bank.
12. A data library system, which has a time-key certificate manager
and a data library and which has a disclosure time control
function, (1) wherein upon receipt of a request from an information
server said time-key certificate manager sends to said information
server a time-key certificate that includes disclosure time
information and a public key for encryption; (2) wherein said data
library receives from said information server encrypted data,
including data that has been encrypted by employing said public key
in said time-key certificate; (3) wherein said data library
transmits said encrypted data to an information user; and (4)
wherein, upon receipt of a request from said information user, said
time-key certificate manager compares a current time with a time
for enabling decryption of said time-key certificate and transmits
a decryption key to said information user when said current time
satisfies a condition for decryption or does not transmit said
decryption key when said current time does not satisfy said
condition for decryption.
13. A time-key management method for guaranteeing that a time for
enabling decryption of information is limited, comprising the steps
of: (1) upon receipt of a request from an information server,
transmitting to an information user a time-key certificate
including disclosure time information and a public key for
encryption; and (2) after said information server transmits to said
information user information encrypted using said public key, which
is included in said time-key certificate, receiving a request for a
decryption key from said information user and transmitting said
decryption key to said information user after said disclosure time
has been reached.
14. A storage medium for storing a program for performing time-key
management to guarantee that a time for enabling decryption of
information is limited, said program comprising: (1) a function
for, upon receipt of a request from an information server,
transmitting to an information user a time-key certificate
including disclosure time information and a public key for
encryption; and (2) a function for, after said information server
transmits to said information user information encrypted using said
public key, which is included in said time-key certificate,
receiving a request for a decryption key from said information user
and for transmitting said decryption key to said information user
after said disclosure time has been reached.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to the field of
encryption. It is more specifically directed to an encryption
system.
BACKGROUND OF THE INVENTION
Background Art
[0002] An explanation will be given for a difference between the
use of a general certificate and the use of a time-key
certificate.
[0003] The use of a general certificate is shown in FIG. 1. When
user B desires to encrypt data (M) and to transmit the encrypted
data to user A, user B requests that a certification authority
issue a certificate for user A. This certificate includes the name
of user A and a public encryption key (KEa) for user A, and also
the digital signature of the certification authority for all the
contents. User B obtains the certificate for user A and confirms
that the certification authority has provided the digital signature
for the public encryption key for user A. If the digital signature
is correct, user B encrypts the target message M by using the
public encryption key (KEa) for user A, and transmits the encrypted
message to user A.
[0004] The general certificate is used to obtain a certain
guarantee for a public encryption key for a partner ("Applied
Cryptography," Bruce Schneier, John Wiley & Suns, Inc., pp.
185-187, 1996), i.e., to provide a guarantee that no person other
than user A can decrypt the encrypted data. However, a condition
for limiting the time during which user A can decrypt data can not
be added to the general certificate.
[0005] One example certificate that includes an encryption key and
time is the Kerberos system ("Computer Network Encryption System,"
Toyohiko Kikuchi, NEC Creative, pp. 57-68, 1995). A server use
permission certificate includes an encryption key, which is used
for encrypting data exchanged between a client machine and a key
authority, and values for "current time" and "valid time."
[0006] While the encryption key in the Kerberos system includes the
subject for encrypting data that are being exchanged, an encryption
key of the present invention includes the subject for inhibiting
decryption at times other than a decryption time. Thus, the
purposes of the keys differ. Furthermore, while the Kerberos system
employs a symmetric key called DES, the present invention employs
an asymmetric key.
[0007] In the Kerberos system, a server use permission certificate
includes a "current time" and a "valid time." The valid time for
the issued server use permission certificate is designated to
prevent the reading of a key. The valid time for present invention,
however, doesn't define time for enabling the decryption of data
that was encrypted using a public encryption key included in the
certificate.
[0008] In ISO X. 400 MHS (http://www.iso.ch/), instruction
identifier "Deferred delivery" is defined as an identifier for
designating a mail delivery time. This is a description method for
designating a time at which mail is to be delivered to an
addressee. The identifier includes only a delivery time for a
destination, and does not include a time for decrypting encrypted
data. With this method, a time for decryption can not be designated
in the certificate.
[0009] The UNIX system has a timed daemon program that synchronizes
clocks at different workstations. This program communicates with a
timed daemon program that is operating in another computer on the
same LAN, and adjusts and synchronizes both clocks. However, since
a daemon program merely adjust clocks, it differs from the time-key
certificate manager of the present invention.
[0010] Then, there is a communication protocol called a network
time protocol (NTP) that synchronizes clocks at workstations that
are not linked together by a LAN ("Building Internet Firewalls," D.
B. Chapman and E. D. Zwicky, pp. 321 to 324, O'Reilly &
Associates, Inc., 1995). According to this protocol, a time
broadcast is received, and a time server that constantly maintains
the clock of a system is employed to adjust the clock of another
system on the Internet to which that system is connected.
Therefore, with this method, a time for enabling decryption of
encrypted data can not be designated.
[0011] And there is a Secure Time-stamping technique that employs a
hash value for a digital document to prove that a document existed
at a specific time ("How To Time-Stamp A Digital Document," S.
Haber and W. S. Stornetta, Advances in Cryptology-CRYPTO 190
Proceedings, Springer-Verlag, pp. 437 to 455, 1991). According to
this technique, when a hash value for a digital document is
transmitted to a system that provides the Secure Time-stamping
service, based on matching of the time-stamping hash value
calculated by the system, it can be proved that the document
existed at a specific time. However, this technique does not teach
a method for designating a time for enabling decryption of
encrypted data.
Problems to be Solved by the Invention
[0012] It is, therefore, one object of the present invention to
provide an encryption system and method for inhibiting the
decryption of encrypted data unless a decryption condition is
satisfied.
[0013] It is another object of the present invention to provide a
disclosure time designation file transfer system.
[0014] It is an additional object of the present invention to
provide a data library system with a disclosure time control
function.
[0015] It is a further object of the present invention to provide a
method and a system for controlling disclosure time.
[0016] It is yet another object of the present invention to provide
a configuration for a time-key certificate and a time-key
certificate manager.
[0017] It is yet an additional object of the present invention to
provide a method for preventing the alteration of data or
wiretapping during the communication process even when data is
encrypted in the same manner as for normal encryption.
[0018] It is yet a further object of the present invention to
provide an encryption system and method for which an ID or a
password, used for an electronic safe system that satisfies a
decryption condition, need not be distributed to a person
performing the decryption.
SUMMARY OF THE INVENTION
[0019] In order to provide an encryption system for inhibiting
decryption of encrypted data unless conditions for decryption are
met, an encryption system with time-dependent decryption is
constructed that has a time-key certificate manager for issuing a
time-key certificate to guarantee that a time for enabling
decryption of information is limited.
[0020] An encryption system according to the present invention is
shown in FIG. 2. User B requests that a time-key certificate
manager (hereinafter referred to simply as a time-key manager)
issue a time-key certificate, including disclosure time
information, and acquires it. Data to be transmitted to user A are
encrypted by using a public key for encryption (KEt) included in
the time-key certificate, and the encrypted data are transmitted.
User A requests a decryption key from the time-key manager to
decrypt the data received from user B. When the current time meets
the decryption conditions, the decryption key is transmitted to
user A, who can use it to decrypt the data.
[0021] As is described above, when the time-key certificate and the
time-key manager are employed, the time during which a third party
can acquire a decryption key for decrypting encrypted data can be
limited.
[0022] In addition, the third party employs a time-key certificate
to examine the public key for encryption included in a time-key
certificate to determine whether or not it satisfies the decryption
conditions. The time-key manager issues a time-key certificate and
then manages a decryption key.
[0023] With this arrangement, a user encrypts data using his or her
machine. And when the user acquires a time-key certificate, he or
she can encrypt data in the same manner as for normal encryption by
using a public encryption key included in the time-key certificate.
As a result, it is possible to provide a system that ensures a high
level of security and that, during the communication process, can
prevent the alteration of data or wiretapping, which can occur when
an external service is employed for encryption.
[0024] Furthermore, when the correct signature of the time-key
certificate manager is included in the time-key certificate, the
user performing the encryption can trust the decryption condition
service provided by the time-key certificate manager that issued
the time-key certificate or by a person in charge of the server, so
that an ID or a password used for an electronic safe system that
satisfies a decryption condition need not be distributed to a
person performing the decryption.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] These and other objects, features, and advantages of the
present invention will become apparent upon further consideration
of the following detailed description of the invention when read in
conjunction with the drawing figures, in which:
[0026] FIG. 1 is a diagram showing the use of a general
certificate;
[0027] FIG. 2 is a diagram showing the use of a time-key
certificate;
[0028] FIG. 3 is a diagram illustrating one embodiment of a
disclosure time designation file transfer system;
[0029] FIG. 4 is a diagram illustrating one embodiment of data
library system having a disclosure date control function;
[0030] FIG. 5 is a schematic diagram illustrating an example
hardware arrangement for a system according to the present
invention;
[0031] FIG. 6 is a diagram for an embodiment of a tendering system
with a disclosure time function;
[0032] FIG. 7 is a diagram for another embodiment of a tendering
system with a disclosure time function;
[0033] FIG. 8 is a diagram for an embodiment of an electronic safe
system with a disclosure time function;
[0034] FIG. 9 is a diagram for another embodiment of an electronic
safe system with a disclosure time function.
DETAILED DESCRIPTION OF THE INVENTION
Preferred Embodiment
[0035] The preferred embodiment of the present invention will now
be described while referring to the drawings. FIG. 5 is a schematic
diagram illustrating an example hardware arrangement for a system
according to the present invention. A system 100 includes a central
processing unit (CPU) 1 and a memory 4. The CPU 1 and the memory 4
communicate across a bus 2 with a hard disk drive 13, which is an
auxiliary storage device. A floppy disk drive (or a memory medium
driver for an MO or a CD-ROM) 20 is connected to the bus 2 via a
floppy disk controller 19.
[0036] A floppy disk (or a memory medium for an MO or a CD-ROM) is
inserted into the floppy disk drive (or a memory medium driver for
an MO or a CD-ROM) 20. Code for a computer program for
accomplishing the present invention can be recorded on the floppy
disk or the hard disk drive 13, or in a ROM 14. The computer
program, which interacts with an operating system to issue commands
to the CPU 1, is loaded into the memory 4 for execution. The code
for the computer program can be compressed, or can be divided into
a plurality of segments to be recorded on a plurality of memory
media.
[0037] The system 100 further includes user interface hardware
components, such as a pointing device (a mouse, a joystick, etc.) 7
or a keyboard 6, and a display 12 for providing visual data for a
user. Furthermore, a printer and a modem can respectively be
connected via a parallel port 16 and a serial port 15. The system
100 can be connected to a network through the serial port 15 and a
modem, or through a communication adaptor card (ethernet or a token
ring) 18 for communication with other computers.
[0038] An audio controller 21 performs D/A (digital/analog)
conversion of an audio signal, and the converted signal is
transmitted to an amplifier 22 for release sound through a
loudspeaker 23. The audio controller 21 also performs A/D
(analog/digital) conversion of audio information received at a
microphone 24, and obtains external audio information for the
system 100.
[0039] As is described above, it would be easily understood that
the encryption system of the present invention can be accomplished
by an ordinary personal computer (PC) or workstation; a notebook
PC; a palmtop PC; a network computer; an electric home appliance,
such as a television incorporating a computer; a game machine
having a communication function; a communication terminal having a
communication function, such as a home telephone, a facsimile
machine, a portable telephone, a PHS terminal or an electronic
notebook; or a combination of such devices. The above described
components are merely examples, and not all the components are
required for the present invention.
[0040] According to the present invention, in order to provide an
encryption system for inhibiting the decryption of encrypted data
unless a decryption condition is satisfied, a decryption enabled
time is a designated decryption condition. The encryption system
with time-dependent decryption is constituted by a time-key
certificate and a time-key certificate manager. The time-key
certificate is employed when a third party proves that an public
encryption key added to the certificate satisfies the decryption
condition. The time-key certificate manager issues the time-key
certificate and then manages a decryption key. The disclosure time
designation file transfer system and the data library system having
a disclosure time control function will now be described as
embodiments of the encryption system with time-dependent
decryption.
[0041] First, the disclosure time designation file transfer system
will be explained. When a user provides information, he or she
believes that the information should be disclosed at a specific
time. As an example, information for personnel changes should not
be disclosed before the date on which it is to be employed.
[0042] When the present invention is employed in this case, upon
the receipt of a request from a user, information for which access
is inhibited until a disclosure time is reached can be encrypted by
using a time-key, and the encrypted data can be transmitted to the
user before the date on which it is employed.
[0043] The processing performed by the system will now be explained
while referring to FIG. 3.
[0044] (1) An information user requests information from an
information server.
[0045] (2) The information server requests that a time-key manger
issue a time-key certificate.
[0046] (3) The time-key manager transmits a time-key certificate to
the information server.
[0047] (4) The information server transmits to the information user
those data, including information M, obtained by encrypting the
time-key certificate using a public key.
[0048] (5) The information user requests that the time-key manager
issue a decryption key.
[0049] (6) The time-key manager transmits a decryption key to the
information user after the disclosure time has been reached.
[0050] (7) The information user decrypts encrypted information M
using the decryption key, and acquires the desired information
M.
[0051] Next, a data library system having a disclosure time control
function will be explained.
[0052] A system for providing to many users data that are acquired
from a plurality of information servers is called a data library
system. In this embodiment, the data library system receives data
from information servers and stores them in a database, and
transmits data to requesters when the requesters are users having
system memberships. Consider a case where, for example, a cameraman
desires to open an exclusive photograph on the data library system
at a specific date, for example since Jan. 1, 1998, but the system
has no control function for a disclosure time.
[0053] A data library system having a disclosure time control
function could be applied in such a case. The processing will now
be described while referring to FIG. 4.
[0054] (1) An information server designates a data discloser period
as a decryption condition. For example, the information server
requests that a time-key certificate manager issue a time-key
certificate that designates Jan. 1, 1998, as the data disclosure
date.
[0055] (2) The information server acquires the time-key certificate
and encrypts the data by using a public encryption key.
[0056] (3) The information server transmits the encrypted data to
the data library system.
[0057] (4) A user accesses the data library system and acquires the
desired encrypted data.
[0058] (5) The user accesses the time-key certificate manager to
request a decryption key.
[0059] (6) The time-key certificate manager compares the current
time with the decryption enabled time contained in the time-key
certificate. When the current time satisfies the decryption
condition, the time-key certificate manager transmits the
decryption key to the user; but when the current time does not
satisfy the condition, the time-key certificate manager does not
transmit the decryption key. Upon the receipt of the decryption
key, the user employs it to decrypt the encrypted data received
from the data library system and obtains the desired data.
[0060] The disclosure time designation file transfer system (FIG.
3), wherein the information user is replaced by an order submitter
and the information server is replaced by an order receiver, can be
employed as an electronic tendering system (FIG. 6). Upon receipt
of a request from an order receiver, the time-key manager transmits
a time-key certificate that includes disclosure time information
and a public key for encryption. The order receiver transmits to an
order submitter tender information that is encrypted using the
public key in the time-key certificate. Then, upon the receipt of a
request from the order submitter for a decryption key, the time-key
manager transmits a decryption key to the order submitter after the
disclosure time has been reached. An electronic tendering system
can therefore be provided that guarantees that a time for enabling
decryption of tender information is limited. In this case, when
tender types differ, a paired public key and secret key differ
accordingly.
[0061] In the electronic tendering system in FIG. 6, when direct
communications among the order submitter, the order receiver and
the time-key manager are to be avoided, only a special tender
manager 710 need be provided for transmitting communications for
the order submitter, the order receiver and the time-key manager
(FIG. 7). In other words, the tender manager exchanges messages
with the order submitter, the order receiver, and the time-key
manager. First, upon receipt of a request from an order receiver,
the tender manager 710 obtains from the time-key manager a time-key
certificate that includes time disclosure information and a public
key for encryption, and transmits the time-key certificate to the
order receiver. Then, the tender manager 710 receives tender
information, which is encrypted by the order receiver using the
public key in the time-key certificate. Upon the receipt of a
request from the order submitter, the tender manager 710 acquires a
decryption key from the time-key manager after the disclosure time
has been reached, and transmits the decryption key to the order
submitter.
[0062] When the information user in FIG. 3 is replaced by a bank
and the information server is replaced by a depositor, the system
can be used as an electronic safe system (FIG. 8). Upon the receipt
of a request from a depositor, the time-key manager transmits to
the depositor a time-key certificate that includes disclosure time
information and a public key for encryption. The depositor
electronically transmits to the bank money information that has
been encrypted using the public key in the time-key certificate.
Then, upon the receipt of a request from the bank for a decryption
key, the time-key manager transmits a decryption key to the bank
after the disclosure time has been reached. Therefore, an
electronic safe system can be provided that guarantees that a time
for decryption of electronic money information is limited. As safes
differ, pairs of public keys and secret keys also differ.
[0063] In the electronic safe system in FIG. 8, when the direct
interchange of messages by the bank, the depositor and the time-key
manager are to be avoided, only a special electronic money manager
910 need be provided for transmitting the messages originating at
the bank, the depositor and the time-key manager (FIG. 9). First,
upon receipt of a request from a depositor, the electronic money
manager 910 receives from the time-key manager a time-key
certificate that includes time disclosure information and a public
key for encryption, and transmits the time-key certificate to the
depositor. Then, the electronic money manager 910 receives
electronic money information, which has been encrypted by the
depositor using the public key in the time-key certificate. Upon
the receipt of a request from the bank, the electronic money manger
910 acquires a decryption key from the time-key manager after the
disclosure time has been reached, and transmits the decryption key
to the bank. The other embodiments can be performed within the
scope of the present invention.
Advantages of the Invention
[0064] Since a user who performs encryption employs the time-key
certificate of the present invention, he or she can encrypt data
using his or her machine. And when the user acquires a time-key
certificate, he or she can encrypt data in the same manner as for
normal encryption by using a public encryption key included in the
time-key certificate. As a result, the alteration of data or
wiretapping during the communication process, which may occur when
an external service is employed for encryption, can be
prevented.
[0065] Furthermore, when the correct signature of the time-key
manager is included in the time-key certificate, the user
performing the encryption can trust the decryption condition
service provided by the time-key manager, which issued the time-key
certificate, or by a person in charge of the server, so that an ID
or a password used for an electronic safe system that satisfies a
decryption condition need not be distributed to a person performing
decryption.
[0066] It is noted that this invention may be used for many
applications. Although the description is made for particular
arrangements and applications, the intent and concept of the
invention is suitable and applicable to other arrangements and
applications. It will be clear to those skilled in the art that
other modifications to the disclosed embodiments can be effected
without departing from the spirit and scope of the invention.
* * * * *
References