U.S. patent application number 10/194444 was filed with the patent office on 2003-06-19 for biometrically enhanced digital certificates and system and method for making and using.
Invention is credited to Howell, Mark J., McCoy, Peter A., Roske, Thorsten, Russo, Anthony P..
Application Number | 20030115475 10/194444 |
Document ID | / |
Family ID | 27378853 |
Filed Date | 2003-06-19 |
United States Patent
Application |
20030115475 |
Kind Code |
A1 |
Russo, Anthony P. ; et
al. |
June 19, 2003 |
Biometrically enhanced digital certificates and system and method
for making and using
Abstract
The present invention provides biometrically enhanced
certificates or other data structure or data item containing
biometric information, by adding fields containing biometric
information derived from a user to a conventional Public Key
Certificate. A biometrically enhanced certificate, therefore,
provides a digital identity that binds a public key not just to a
name, but to a physical property or properties of the person or
entity who is the subject of the certificate. In one embodiment,
biometric certificate fields comprising biometric data are
incorporated into private extensions of an X.509 identity
certificate. In another embodiment, biometric certificate fields
comprising biometric data are incorporated into an X.509 attribute
certificate.
Inventors: |
Russo, Anthony P.; (New
York, NY) ; Howell, Mark J.; (Tucson, AZ) ;
Roske, Thorsten; (Munchen, DE) ; McCoy, Peter A.;
(Santa Cruz, CA) |
Correspondence
Address: |
DORSEY & WHITNEY LLP
Suite 3400
Four Embarcadero Center
San Francisco
CA
94111-4187
US
|
Family ID: |
27378853 |
Appl. No.: |
10/194444 |
Filed: |
July 12, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10194444 |
Jul 12, 2002 |
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10099554 |
Mar 13, 2002 |
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10194444 |
Jul 12, 2002 |
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10099558 |
Mar 13, 2002 |
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60305120 |
Jul 12, 2001 |
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Current U.S.
Class: |
713/186 |
Current CPC
Class: |
H04L 2209/805 20130101;
G06Q 30/06 20130101; H04L 2209/08 20130101; G06V 40/1335 20220101;
G06Q 20/4016 20130101; G06Q 20/04 20130101; H04L 9/3231 20130101;
G06Q 10/02 20130101 |
Class at
Publication: |
713/186 |
International
Class: |
H04K 001/00 |
Claims
We claim:
1. A digital certificate for use in a public key infrastructure,
said certificate comprising: a public key field comprising a public
key; and a biometric certificate field comprising biometric data;
wherein said public key and said biometric data are associated with
a same entity.
2. A certificate according to claim 1, wherein said biometric data
comprises processed biometric data.
3. A certificate according to claim 2, wherein said biometric data
comprises a biometric template.
4. A certificate according to claim 2, wherein said biometric data
comprises a hash value.
5. A certificate according to claim 1, wherein said biometric data
comprises a raw biometric data sample.
6. A certificate according to claim 1, wherein said certificate is
an X.509 certificate comprising private extensions, and wherein
said private extensions comprise said biometric information.
7. A certificate according to claim 1, wherein said certificate is
an X.509 certificate associated with an X.509 attribute certificate
containing said biometric information.
8. A certificate according to claim 6, wherein said biometric
information comprises a biometric template.
9. A certificate according claim 7, wherein said biometric
information comprises a biometric template.
10. A certificate according to claim 6, wherein said biometric
information comprises a hash value.
11. A certificate according to claim 7, wherein said biometric
information comprises a hash value.
12. A certificate according to claim 1, wherein said biometric data
is based on a biometric data sample.
13. A certificate according to claim 12, wherein said biometric
data sample comprises a fingerprint scan.
14. A certificate according to claim 12, wherein said biometric
data sample comprises a facial image.
15. A certificate according to claim 12, wherein said biometric
data sample comprises an iris scan.
16. A certificate according to claim 12, wherein said biometric
data sample comprises a voice recording.
17. A method for generating a biometrically enhanced certificate
comprising: obtaining a biometric data sample; processing said
biometric data sample to yield processed biometric information;
generating biometric certificate fields utilizing said compressed
biometric information; and submitting certificate information
including said biometric certificate fields to at least one
third-party authority.
18. A method according to claim 17, further comprising: generating
a public/private key pair.
19. A method according to claim 17, wherein said processing
comprises applying a hash function to said biometric data sample
and said processed biometric data comprises a hash value.
20. A method according to claim 17, wherein said processing
comprises extracting a biometric template from said biometric data
sample.
21. A method according to claim 20, wherein said processing further
comprises encrypting said biometric template with said public
key.
22. A method according to claim 17, wherein said generating
biometric certificate fields comprises generating private
extensions for an X.509 identity certificate, wherein said private
extensions comprise processed biometric data.
23. A method according to claim 17, wherein said generating
biometric certificate fields comprises generating an attribute
certificate corresponding to an X.509 base certificate, wherein
said attribute certificate comprises processed biometric data.
24. A method according to claim 17, further comprising receiving a
signed certificate.
25. A computer program product for use in conjunction with a
computer system having at least one processor and a memory coupled
to the processor, the computer program product comprising a
computer readable storage medium and a computer program mechanism
embedded therein, the computer program mechanism, comprising: a
program module that directs the computer to function in a specified
manner to generate a biometrically enhanced certificate, the
program module including instructions for: obtaining a biometric
data sample; processing said biometric data sample to yield
processed biometric information; generating biometric certificate
fields utilizing said compressed biometric information; submitting
certificate information including said biometric certificate fields
to at least one third-party authority; and receiving a signed
certificate.
26. A computer program product according to claim 25, wherein the
program module further including instructions for: generating a
public/private key pair.
27. A computer program product according to claim 25, wherein the
program module further including instructions for applying a hash
function to said biometric data sample and said processed biometric
data comprises a hash value.
28. A computer program product according to claim 25, wherein the
program module further including instructions for extracting a
biometric template from said biometric data sample.
29. A computer program product according to claim 25, wherein the
program module further including instructions for encrypting said
biometric template with said public key.
30. A computer program product according to claim 25, wherein the
instructions for generating biometric certificate fields comprises
instructions for generating private extensions for an X.509 base
certificate, wherein said private extensions comprise processed
biometric data.
31. A computer program product according to claim 25, wherein said
instructions for generating biometric certificate fields comprises
instructions for generating an attribute certificate corresponding
to an X.509 base certificate, wherein said attribute certificate
comprises processed biometric data.
32. A digital certificate for use in a public key infrastructure,
said certificate comprising: a public key field comprising a public
key; a biometric certificate field comprising scan sampled
biometric data including processed biometric data, a biometric
template, and a hash value; wherein said public key and said
biometric data are associated with a same entity; said certificate
is an X.509 certificate comprising private extensions, and wherein
said private extensions comprise said biometric information; and
said biometric data sample comprises a biometric data sample
selected from the group consisting of a fingerprint scan, a facial
image, an iris scan, a retinal scan, a voice recording, a DNA
sample, a saliva sample, and combinations thereof.
33. A method for generating a biometrically enhanced certificate
according to claim 17, wherein the biometrically enhanced
certificate comprises a digital biometrically enhanced certificate
for use in a public key infrastructure comprising: a public key
field comprising a public key; a biometric certificate field
comprising scan sampled biometric data including processed
biometric data, a biometric template, and a hash value; wherein
said public key and said biometric data are associated with a same
entity; said certificate is an X.509 certificate comprising private
extensions, and wherein said private extensions comprise said
biometric information; and said biometric data sample comprises a
biometric data sample selected from the group consisting of a
fingerprint scan, a facial image, an iris scan, a retinal scan, a
voice recording, a DNA sample, a saliva sample, and combinations
thereof.
Description
BACKGROUND OF THE INVENTION
[0001] The security and integrity of information systems depends in
part on authentication of individual users--accurately and reliably
confirming or authenticating the identity of a user attempting to
use the system. Once a user is authenticated, a system is then able
to authorize the user to retrieve certain information or perform
certain actions appropriate to the system's understanding of the
user's identity. Examples of such actions include downloading a
document, completing a financial transaction, or digitally signing
a purchase.
[0002] Numerous methods have been developed for authenticating
users. Generally, as will be understood by those skilled in the
art, authentication methods are grouped into three categories, also
called authentication factors, see for example Smith, Richard E.,
"Authentication: from Passwords to Public Keys" Addison-Wesley,
2002, p. 29, incorporated herein by reference in its entirety. The
three categories are generally: 1) something you know--a secret
such as a password or a PIN or other information; 2) something you
have--such as a smartcard, the key to a mechanical lock, an ID
badge, or other physical object; and 3) something you are--a
measure of a person such as a fingerprint or voiceprint. Each
method has advantages and disadvantages including those relating to
ways that a system may be fooled into accepting a normally
unauthorized user in cases where, for example, a password has been
guessed or a key has been stolen.
[0003] The third category above--referred to herein as `something
you are` authentication methods--are the subject of the biometrics
field. Biometric identification is used to verify the identity of a
person by measuring selected features of some physical
characteristic and comparing those measurements with those filed
for the person in a reference database or stored in a token (such
as a smartcard) carried by the person. Physical characteristics
that are used today include fingerprints, voiceprints, hand
geometry, the pattern of blood vessels on the wrist or on the
retina of the eye, the topography of the iris of the eye, facial
patterns, and the dynamics of writing a signature or typing on a
keyboard. Biometric identification methods are widely used today
for securing physical access to buildings and securing data
networks and personal computers.
[0004] The security and integrity of information systems also
depend on keeping data confidential so that only authorized users
may see or act against the data, and assuring the integrity of data
so that the data cannot be changed or tampered with undetected. The
field of cryptography provides tools for assuring confidentiality
and integrity using encryption techniques such as ciphers and hash
algorithms.
[0005] One widely known and implemented body of these tools, and
procedures and practices for their use, is called Public Key
Infrastructure (PKI). PKI gets its name from its use of a class of
cryptographic algorithm called a public key algorithm. As is widely
known to those versed in the cryptographic field, a public key
algorithm is a cryptographic algorithm that operates using two
different but mathematically-related keys, a public key that may be
shared with any party and a private key which must be kept secret,
such that (for must such algorithms) data encrypted with the public
key may only be decrypted with the private key, and vice-versa. PKI
standards are well known, X.509 for example, described in Housley,
R., "Internet X.509 Public Key Infrastructure Certificate and CRL
Profile," RFC 2459, January 1999, and ITU-T Recommendation X.509
(1997 E): Information Technology--Open System Interconnection--The
Directory: Authentication Framework, June 1997, both of which are
hereby incorporated by reference.
[0006] These standards provide powerful mechanisms for safe and
private storage and transmission of confidential data so that it
remains hidden from unauthorized parties. The standards provide for
digital signatures, which provide the receiving party of some data
with an assurance of the identity of the transmitting party. PKI
standards further provide for digital certificates, which provide a
tamper-resistant, portable record of the association of a public
key with a person's or organization's name, attested to and signed
by a trusted party, thus presenting a form of unique, irrefutable
digital identity or credential for that person or organization. PKI
standards also provide other useful and powerful mechanisms that
can contribute to the security and integrity of information
systems. On example of a certificate for use in a PKI system is an
X.509 certificate.
[0007] FIG. 1 schematically depicts a standard X.509 certificate
101, herein referred to as an `identity certificate`, containing
fields for Version 102, Certificate Serial Number 103, Signature
Algorithm Identifier 104, Issuer Name 105, Validity Period 106,
Subject Name 107, Subject Public Key Info 108, Issuer Unique
Identifier 109, and Subject Unique Identifier 110. This general
structure is known in the art. Contents of the certificate are
signed by the issuing certificate authority (CA), and the signature
is found in the CA Signature field 112. This figure is for
reference and is not intended to provide a complete or
authoritative definition of the structure or contents of an X.509
certificate.
[0008] PKI is widely used in commercial and non-commercial systems,
both over the Internet and in more closed or local applications.
Most web browsers, for example, use PKI and PKI-based standards to
interoperate with web servers when high security is desired, as
when a user specifies a credit card number for payment while
placing an online order. The proliferation of electronic commerce
has led many jurisdictions around the world to begin to develop
legal standards with the intended result that a correctly
constituted digital signature would be every bit as legally binding
as a handwritten signature is today.
[0009] PKI provides powerful mechanisms, but it has weaknesses. In
practice, digital certificates are issued to persons or
organizations by a Certificate Authority (CA), usually a trusted
third party in the business of providing a measured degree of
assurance that the digital identity embodied in the certificate is
valid and genuine. With such an assurance, a party may be confident
that someone who claims a certain identity and presents a digital
certificate is in fact that person or organization and not an
impostor.
[0010] The assurance of a third-party Certificate Authority can be
compromised, as it is based on assumptions that may turn out to be
invalid. For example, if a CA issues a certificate to an imposter,
that would invalidate the assumption that the CA has successfully
and correctly verified the party to whom it is issuing the
certificate. Often, certificates refer to a person by name, and may
include other information such as an address. One's name has a
meaning by social convention and in legal terms, but a name is not
an intrinsic property of a physical person. Persons can assume
names or change names, for example, creating a vulnerability in
certificates utilizing names. Nor are names guaranteed to be
unique; many people have names that are the same as those of other
people. Linking a digital identity of a party to a name, address,
or other ambiguous, extrinsic, or easily assumed or changed
attribute of the party can present opportunities for impostors in
PKI systems.
[0011] Another way for digital identities to be compromised is for
an impostor to somehow get a copy of the private key that is
associated with the public key embedded in a certificate, thus
invalidating an assumption that only the person or organization to
which the certificate is issued has access to the (secret) private
key. Anyone with both the certificate (which is meant to be public
information, freely exchanged with anyone) and the associated
private key (which is meant to be secret) can impersonate someone
else and compromise the security and integrity of an information
system dependent on the valid use of a certificate and associated
private key.
[0012] Most systems, therefore, secure the private key such that
the user must authenticate before the private key can be used for
any task. Many such systems require a password ("something you
know") or a smartcard ("something you have") or both. Some systems
provide additional security by putting the private key on a
smartcard that is resistant to tampering or copying. However, smart
cards may be lost, damaged, or stolen. Passwords may be forgotten
or guessed. These concerns are part of what is called in the field
"the last-meter problem", the problem of making sure that an
otherwise secure system isn't compromised by a failure to correctly
authenticate the person using (and usually physically adjacent to)
some part of the system. The last-meter problem can present
opportunities for impostors in PKI systems.
[0013] Accordingly, there is a need in the art for a system
offering improved security for the certification process. Such a
system would preferably be compatible with PKI systems.
SUMMARY OF THE INVENTION
[0014] In a first aspect, the present invention provides a digital
certificate for use in a public key infrastructure, said
certificate comprising a public key field comprising a public key;
and a biometric certificate field comprising biometric data;
wherein said public key and said biometric data are associated with
a same entity.
[0015] In some embodiments, said biometric data comprises processed
biometric data. The processed biometric data may include a
biometric template. Alternatively, or in addition, said biometric
data may comprise a hash value in some embodiments of the
invention.
[0016] In other embodiments, said biometric data comprises a raw
biometric data sample.
[0017] In one embodiment, said certificate is an X.509 certificate
comprising private extensions, wherein said private extensions
comprise said biometric information. In one embodiment, said
biometric information comprises a biometric template. In other
embodiments, said biometric information comprises a hash value.
[0018] In another embodiment, said certificate is an X.509
certificate associated with an X.509attribute certificate
containing said biometric information. In one embodiment, said
biometric information comprises a biometric template. In other
embodiments, said biometric information comprises a hash value.
[0019] In some embodiments, said biometric data is based on a
biometric data sample. The biometric data sample may comprise a
fingerprint scan, a facial image, an iris scan, a voice recording,
or combinations thereof.
[0020] In another aspect of the present invention, a method is
provided for generating a biometrically enhanced certificate
comprising obtaining a biometric data sample, processing said
biometric data sample to yield processed biometric information,
generating biometric certificate fields utilizing said compressed
biometric information, and submitting certificate information
including said biometric certificate fields to at least one
third-party authority.
[0021] Some embodiments of the method further comprise generating a
public/private key pair. Other embodiments further comprise
receiving a signed certificate.
[0022] In some embodiments, processing a biometric data sample
comprises applying a hash function to said biometric data sample
and said processed biometric data comprises a hash value. In other
embodiments, said processing comprises extracting a biometric
template from said biometric data sample. In still other
embodiments, said processing further comprises encrypting said
biometric template with said public key.
[0023] In some embodiments, generating biometric certificate fields
comprises generating private extensions for an X.509 identity
certificate, wherein said private extensions comprise processed
biometric data. In other embodiments, said generating biometric
certificate fields comprises generating an attribute certificate
corresponding to an X.509 base certificate, wherein said attribute
certificate comprises processed biometric data.
[0024] In still more embodiments, the certificate provided by the
method is a digital biometrically enhanced certificate comprising a
public key field comprising a public key, a biometric certificate
field comprising scan sampled biometric data including processed
biometric data, a biometric template, and a hash value; wherein
said public key and said biometric data are associated with a same
entity, said certificate is an X.509 certificate comprising private
extensions, said private extensions comprise said biometric
information, and said biometric data sample comprises a biometric
data sample selected from the group consisting of a fingerprint
scan, a facial image, an iris scan, a retinal scan, a voice
recording, a DNA sample, a saliva sample, and combinations
thereof.
[0025] In yet another aspect of the present invention, a computer
program product for use in conjunction with a computer system
having at least one processor and a memory coupled to the processor
is provided, the computer program product comprising a computer
readable storage medium and a computer program mechanism embedded
therein, the computer program mechanism, comprising a program
module that directs the computer to function in a specified manner
to generate a biometrically enhanced certificate, the program
module including instructions for obtaining a biometric data
sample, processing said biometric data sample to yield processed
biometric information, generating biometric certificate fields
utilizing said compressed biometric information, submitting
certificate information including said biometric certificate fields
to at least one third-party authority, and receiving a signed
certificate.
[0026] In some embodiments, the program module further includes
instructions for generating a public/private key pair.
[0027] In other embodiments, the program module further includes
instructions for applying a hash function to said biometric data
sample and said processed biometric data comprises a hash value. In
still other embodiments, the program module further includes
instructions for extracting a biometric template from said
biometric data sample. In yet other embodiments, the program module
further including instructions for encrypting said biometric
template with said public key.
[0028] In some embodiments, the instructions for generating
biometric certificate fields comprise instructions for generating
private extensions for an X.509 base certificate, wherein said
private extensions comprise processed biometric data. In other
embodiments, said instructions for generating biometric certificate
fields comprise instructions for generating an attribute
certificate corresponding to an X.509 base certificate, wherein
said attribute certificate comprises processed biometric data.
[0029] In yet another aspect of the present invention, a digital
certificate for use in a public key infrastructure is provided,
said certificate comprising a public key field comprising a public
key, a biometric certificate field comprising scan sampled
biometric data including processed biometric data, a biometric
template, and a hash value, wherein said public key and said
biometric data are associated with a same entity, said certificate
is an X.509 certificate comprising private extensions, and wherein
said private extensions comprise said biometric information, and
said biometric data sample comprises a biometric data sample
selected from the group consisting of a fingerprint scan, a facial
image, an iris scan, a retinal scan, a voice recording, a DNA
sample, a saliva sample, and combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The present invention may be better understood, and its
features and advantages made apparent to those skilled in the art
by referencing the accompanying drawings.
[0031] FIG. 1 is a schematic depiction of a general structure for
an embodiment of a standard X.509 certificate.
[0032] FIG. 2 is a schematic depiction of an embodiment of a
biometrically enhanced certificate according to the present
invention comprising an X.509 identity certificate having private
extensions comprising biometric certificate fields.
[0033] FIG. 3 is a schematic depiction of an embodiment of a
biometrically enhanced certificate according to the present
invention comprising an X.509 attribute certificate.
[0034] FIG. 4 is a schematic overview of a method for creating a
biometrically enhanced certificate, according to an embodiment of
the present invention.
[0035] FIG. 5 is a schematic illustration of a method for creating
a biometrically enhanced certificate embodied as an X.509 identity
certificate comprising private extensions comprising biometric
certificate fields, according to an embodiment of the present
invention.
[0036] FIG. 6 is a schematic illustration of a method for creating
a biometrically enhanced certificate comprising an X.509 attribute
certificate, according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0037] The present invention provides certificates or other data
structure or data item for use in public key infrastructures. It
also provides methods for making and using such certificates as
well as computer program and computer program product for making
and using such certificates.
[0038] By `public key infrastructure` (PKI), herein is meant
generally any security system employing public key algorithms--with
X.509 being one specific embodiment of a PKI. Public key
algorithms, as used herein, generally refers to any algorithm
utilizing a public-private key pair wherein two keys are stored in
separate locations. That is, generally, in a transaction involving
a receiving party and a transmitting party, a private key is known
to the transmitting party but not the receiving party, while a
public key is known to both parties. By `key` herein is meant
data--typically in the form of a code, or string of
digits--utilized in a cryptographic procedure. Thus, some
embodiments of the present invention are intended for use in a PKI
system where a private key (known only to a transmitting party), is
utilized to encrypt a message, and a corresponding public key
(known to both parties), is utilized to decrypt the message. In
other embodiments, a private key is used to decrypt while a public
key is used to encrypt a message.
[0039] Briefly, the present invention utilizes a combination of
biometrics and PKI to address the known weaknesses of existing
authentication systems, bridging the "last meter" between secured
systems and their users. Accordingly, the present invention
provides biometrically enhanced certificates or other data
structure or data item containing biometric information, by adding
fields containing biometric information derived from a user to a
conventional Public Key Certificate (also referred to herein as an
`ID Certificate` or `Identity Certificate`). Requirements for a
suitable identity certificate are generally only that the identity
certificate contain a public key usable in a public key
infrastructure. The identity certificate generally links a key pair
with an identity--for example, a name, address, corporate
identification, organization identifier, or the like. Other fields
in an identity certificate will be determined by the particular
protocol and system used. One example of an embodiment of an X.509
identity certificate is shown in FIG. 1 and is discussed above. A
biometrically enhanced certificate, therefore, provides a digital
identity that is superior to a typical digital certificate because
it binds a public key not just to a name, but to a physical
property or properties of the person who is the subject of the
certificate.
[0040] Biometrically enhanced certificates, then, comprise
biometric information derived or obtained from a raw biometric data
sample. A raw biometric data sample refers to a set of data
generated by a sampling event or other acquisition. The type and
structure of a raw biometric data sample will generally be
dependent on the type of biometric sensor or acquisition device
used to take the biometric data sample, and the data collection
mechanisms. Suitable raw biometric data samples include fingerprint
scans, voice samples, facial images, signature images, iris scans,
and retinal scans. Generally, any dataset that provides a unique
`who you are` measure of a user can be used--including all or
portions of a genetic sequence, for example. A wide array of
technologies are available to provide biometric data verification
including fingerprint, voice, face, signature, iris, retina
verification, and other biometric technologies.
[0041] In some embodiments of the invention, more than one kind of
biometric within one biometrically enhanced certificate (a
fingerprint scan as well as a voice sample, for example) is
sampled. In embodiments where a plurality of biometrics are sampled
(either two types of biometric, or two samples of a same biometric,
such as two fingerprint scans), a plurality of biometric
certificate fields may be generated, as described further below.
Further, biometric fields may be combined with conventional fields
containing biographical information such as name, address, and the
like.
[0042] In embodiments of the present invention, a raw biometric
data sample itself may be utilized in a biometric certificate
field. However, it is undesirable to make a biometric data sample
public--or to allow insecure access, or increase a risk of insecure
access, to a biometric data sample. Accordingly, biometric data
samples can be processed, yielding processed biometric information,
or processed biometric data, as used herein. This processed
biometric data may also referred to in the art as a `biometric
template`, discussed further below.
[0043] Processed biometric information generally refers to
biometric data derived from one or more raw biometric data samples.
In one embodiment, processed biometric information is generally
more compact than a raw biometric data sample. In other
embodiments, processed biometric information refers to a unique
identifier of a biometric data sample that cannot be utilized to
reconstruct the biometric data sample. In still other embodiments,
processed biometric information is both more compact than the
original sample and uniquely identifies the sample while it cannot
be used to reconstruct the sample. In other embodiments, processed
biometric information is encrypted raw biometric data.
[0044] Accordingly, in preferred embodiments of the present
invention, processed biometric information utilized in a biometric
certificate field includes a biometric template, which generally
refers to a distillation of unique characteristics of a biometric
data sample, produced by a known biometric algorithm. For example,
a fingerprint template may contain a list of minutiae points
detected in a fingerprint image. Other template-generating
algorithms are known in the art for fingerprint templates, and for
other biometrics, as is described, for example, in A. K. Jain, L.
Hong, S. Pankanti and R. Bolle, "An Identity Authentication System
Using Fingerprints", Proc. IEEE Vol. 85, No. 9, pp. 1365-1388,
1997; and D. Maio, D. Maltoni, "Direct Gray-scale Minutiae
Detection in Fingerprints",IEEE Trans. On Pattern Analysis and
Machine Intelligence, Vol. 19, No. 1, pp. 27-40, 1997, both of
which are hereby incorporated by reference. Templates are
advantageously but optionally encrypted--using either a public or
private key--prior to their inclusion in a biometrically enhanced
certificate. In some embodiments, the biometric template is
encrypted with the user's public key and put in a certificate
Encrypted Template field. Since an encrypted template field is
encrypted with the user's public key, it can only be decrypted with
the user's corresponding private key, thus making it only
accessible by or on behalf of the user. In other embodiments, a
biometric template is encrypted with a trusted server's public key
and put in a certificate's Encrypted Template field. Since this
field is encrypted with the server's public key, it can only be
decrypted with the server's corresponding private key, thus making
it only accessible by the trusted server. In another embodiment,
two biometric certificate fields are created from one raw biometric
data sample--one comprising a biometric template encrypted with a
user's public key, and another comprising a biometric template
encrypted with a server's public key.
[0045] In other preferred embodiments of the present invention,
processed biometric information utilized in a biometric certificate
field include a hash value, computed by a hash function. In these
embodiments, a biometric sample is acquired and processed by a hash
function such as MD5, discussed in Rivest, R., "The MD5
Message-Digest Algorithm," RFC 1321, April 1992, hereby
incorporated by reference, or SHA-1, defined in "Secure Hash
Standard," Federal Information Processing Standards Publication
180-1, April 1995, hereby incorporated by reference. The hash
function computes a hash value of the user's biometric sample,
which is put in the certificate's Biometric Hash Value field. A
preferred embodiment utilizes SHA-1 to compute biometric hash
values. In preferred embodiments, the original, raw, biometric data
sample is stored in a secure reference database, but this is not
required.
[0046] A hash value cannot be utilized to reconstruct the original
biometric data sample, but is unique to the sample; therefore, the
hash value can be made public, such as by embedding within a
digital certificate. If a biometric sample is successfully matched
against the original biometric sample stored in a secure reference
database, and the hash value of this original sample is identical
with the value of this field, it is proven that the biometrically
enhanced certificate was indeed created for that user. That is, in
order to later prove (as in the case of repudiation of a
transaction, described further below), that a particular biometric
data sample was in fact utilized to generate a certain
biometrically enhanced certificate, a hash value for that biometric
data sample is generated and compared with the hash value contained
in the biometrically enhanced certificate. The hash values will
match if the biometric data sample in question was used in
preparation of the biometrically enhanced certificate. Matching a
subsequent biometric data sample taken from a user to the stored
biometric sample utilized to generate the biometrically enhanced
certificate verifies that the biometrically enhanced certificate
was created for the user whose subsequent biometric data sample was
taken.
[0047] Other embodiments of the invention provide biometrically
enhanced certificates comprising a hash value and a biometric
template.
[0048] Further, it is desirable for servers (or other devices
receiving a biometrically enhanced certificate) to receive an
indication of a trust level for an original enrollment of biometric
data. Under certain circumstances, it may be possible for imposters
during enrollment to substitute their own biometric data for that
of the certificate's intended owner, thereby causing a breach in
the integrity of the biometrically enhanced certificate. Therefore,
it is advantageous for embodiments of the present invention to
provide biometrically enhanced certificates with an optional
enrollment field providing an indication of the trustworthiness of
a particular enrollment process. That is, biometric data that was
enrolled in a less secure manner will generally receive a lower
trust level, while more secure enrollment procedures will receive a
higher trust level. The enrollment field, then, allows recipients
of the biometrically enhanced certificate to allow access or
authenticate users based on not only a biometric data match, but
also a biometric data match made at or above a certain trust level.
While ascertaining and acting on a trust level in an enrollment
process is discussed here, related methods and systems for
determining confidence or trust levels in a transaction are
discussed in U.S. application Ser. No. 10/___,___, filed ______,
entitled "Method And System For Determining Confidence in a Digital
Transaction" (Attorney Docket No. A-70779/RMA/JML), hereby
incorporated by reference.
[0049] Accordingly, enrollment field, as used herein, refers to a
certificate field containing information on how a user was
enrolled. A measure of the overall reliability and trustworthiness
of the biometrically enhanced certificate is provided by the
enrollment method. Hence to be able to judge the trustworthiness of
the biometrically enhanced certificate, an enrollment field
contains information on how the user was enrolled. The enrollment
method is generally represented as a symbolic value within the
field corresponding to the actual enrollment method used. The
following is a subset of possible enrollment methods:
[0050] Self-enrollment. A user enrolls using a computer which is
wireline connected to the Internet, or with his wireless device
(such as a personal digital assistant (PDA) or cellular phone) with
a wireless Internet connection or wireless PC connection, such as
802.11. This represents the least secure method of this subset, and
would receive the `lowest`trust value.
[0051] Self-enrollment using an enrollment secret. In this case, as
above, a user enrolls using a device connected via a wireline or
wireless Internet or PC connection to the Internet. However, in
order to successfully complete the enrollment process the user has
received a secret (e.g. a PIN, password, or other secret
information) from a trusted source (for example from the user's
bank) over a different channel (for example, via postal mail,
e-mail, or the like). This is a basic method of enrollment for
ensuring a level of trust and confirms the enrollment secret was
received. Accordingly, this `secret` enrollment method would
receive a higher trust level than basic self-enrollment above, but
a lower trust level than methods in this subset discussed
below.
[0052] Self-enrollment using smart cards or SIM cards. In this
case, as above, a user enrolls using a device connected via a
wireline or wireless Internet or PC connection to the Internet or
server device. However, in this case a pre-configured smart card or
SIM card is used to establish additional trust in the enrollment
process and the data provided by the user. Accordingly, this `smart
card` method would receive a higher level of trust than methods in
the subset discussed above, but a lower level than methods
discussed below. The smart card or SIM card may advantageously
comprise a write-only memory where the required enrollment data is
stored, increasing the trust level of this method.
[0053] Face-to-face enrollment. In this method, enrollment is
performed by a trusted human representative such as an employee in
a bank branch, notary public, government official, or other trusted
person. The user's documentation is reviewed and verified. This is
the strongest level of trust presented in this subset, and would
receive the highest trust value of the subset.
[0054] Specific trust level values depend on the system deployed.
In some cases, it may be advantageous to have one or more
enrollment methods receive the same trust level--even if one is
theoretically more or less secure than another. For example, in one
embodiment, a smart card enrollment process, a `secret` enrollment
process, and a basic self-enrollment process receive a first base
trust level, and face-to-face enrollment receives a higher trust
level. In this manner, a system can support many enrollment
procedures, but a simplified trust tier. In other embodiments, a
higher trust level may be given to enrollment processes which are
theoretically less secure than those given a lower trust level--for
example if an institution wants to encourage use of a particular
enrollment process despite its lower security level.
[0055] Specific embodiments of biometrically enhanced certificates
are discussed below with regard to an X.509 standard. The X.509
standard is utilized here to illustrate and exemplify the
invention, and is not intended to limit the practice of the
invention to a single protocol.
[0056] A preferred embodiment of a biometrically enhanced
certificate builds on X.509 digital certificates (see Housley, R.,
"Internet X.509 Public Key Infrastructure Certificate and CRL
Profile," RFC 2459, January 1999, and ITU-T Recommendation X.509
(1997 E): Information Technology--Open Systems Interconnection--The
Directory: Authentication Framework, June 1997, both of which are
hereby incorporated by reference), and can be understood generally
as having two components: (1) standard fields of an X.509 Identity
Certificate or Attribute Certificate depending on the chosen method
of implementation; and (2) additional biometric certificate fields
which link the certificate to its human referent by the biometric
information contained in those fields.
[0057] The implementation of additional biometric-related
information can take the form of X.509 private extensions, or an
X.509 Attribute Certificate. In other embodiments where X.509 is
not the chosen PKI system, biometric-related information would be
added to the certificate in a manner compatible with the chosen PKI
system.
[0058] A standard X.509 certificate, or `identity certificate`, is
discussed above with reference to FIG. 1. It is noted that FIG. 1
represents one embodiment of an identity certificate including some
optional fields. In some embodiments, not all fields shown in FIG.
1 are present in the identity certificate. In other embodiments,
other fields not shown in FIG. 1 are present. biometrically
enhanced certificates according to preferred X.509 embodiments of
the present invention generally fall into two groups: X.509
certificates with private extensions and X.509certificates with
attribute certificates. These groups are intended to demonstrate
two potential embodiments of the present invention. Those skilled
in the art will readily recognize that biometric data may similarly
be incorporated into certificates according to other protocols.
Further, in some cases a certificate may have attributes of both
the groups described below that is comprise both private extensions
and attribute certificates.
[0059] Accordingly, one embodiment of the present invention
provides biometrically enhanced certificates comprising an X.509
certificate with private extensions. The ability to add data
elements to an X.509 certificate is described in ITU-T
Recommendation X.509 (1997E): Information Technology--Open Systems
Interconnection--The Directory: Authentication Framework, June
1997, incorporated herein by reference. These added data elements,
called private extensions, can be identified as critical or
non-critical depending on whether applications are required to work
with the extensions or if they may be allowed to ignore the
extensions. In some preferred embodiments of the present invention,
biometric certificate fields are identified as critical. In other
preferred embodiments, some or all biometric certificate fields are
identified as non-critical.
[0060] FIG. 2 depicts a schematic illustration of biometrically
enhanced certificate 113 that comprises private extensions 111 that
add biometric information to a standard X.509 identity certificate.
For example, private extensions 111 may include biometric hash
value field 115, one or more encrypted biometric template fields,
such as encrypted template fields 116 and 117 (where template field
116 comprises template data encrypted with a user's public key, and
template field 117 comprises template data encrypted with a
server's public key, as discussed above), and an enrollment type
field 118, which indicates a trust level for the enrollment of
biometric information. Hash values templates, and enrollment types
are discussed further above. The collection of biometric
certificate fields shown in FIG. 2 is one embodiment of such a
collection of fields. Some or all of the fields may be unnecessary
in other embodiments. The biometric related fields added as private
extensions may be marked as critical or non-critical depending on
the specific requirements envisaged for a biometrically enhanced
certificate system. In a preferred embodiment, all fields
containing biometric information (either the raw biometric data or
the biometric template) are identified as critical.
[0061] In another embodiment of the present invention, biometric
information is provided as an X.509 attribute certificate. As
defined in the relevant standards, an Attribute Certificate is very
similar to a standard identity certificate with the main difference
that an Attribute Certificate does not include the public key of
the owner (as identity certificates do). Instead, an Attribute
Certificate is uniquely linked to an identity certificate, which is
then referred to as a base certificate. In addition, an Attribute
Certificate is signed by an Attribute Authority that does not need
to be the same entity as the Certificate Authority that signed the
base certificate. FIG. 3 schematically depicts Attribute
Certificate 114 containing biometric related fields--such as
biometric hash value field 115, encrypted template fields 116 and
117, and enrollment field 118. Attribute certificate 114 further
may include a variety of other fields--including version field 102,
holder field 123, certificate issuer field 105, algorithm
identifier field 104, and certificate serial number field 103. FIG.
3 also depicts base certificate 101 with which Attribute
Certificate 114 is associated. The base and attribute certificates
are associated through one or more fields. In a preferred
embodiment the base and attribute certificates are associated, as
defined in X.509, by the attribute certificate's Holder field 123
which contains either the issuer and serial number 103 or entity
name 107 of the base certificate 101, or both.
[0062] In some embodiments, a single biometrically enhanced
certificate represents a plurality of identities, or users. That
is, a single biometrically enhanced certificate may include
biometric data associated with more than one person or entity. In
these embodiments biometric fields 115-118 are repeated for each
shared owner of the biometrically enhanced certificate, as
appropriate. An additional Number field may be included indicating
the number of shared owners.
[0063] A biometrically enhanced certificate may have, but is not
required to have, all fields discussed above. Additionally, those
skilled in the art will readily identify other potential field
types containing biometric data. Any one or more of the above
described fields added to a certificate constitutes a biometrically
enhanced certificate.
[0064] The present invention further provides methods for creating
biometrically enhanced certificates. The methods are generally
similar to those for creating a normal digital certificate with
additional steps for acquiring and handling biometric information.
The specific process is dependent on the chosen implementation of
the biometrically enhanced certificate, such as X.509.
[0065] FIG. 4 generally depicts methods for creating biometrically
enhanced certificates as provided by embodiments of the present
invention. Briefly, the fields for a standard identity certificate
are generated in step 500. As discussed above, an identity
certificate is generally any certificate suitable for use in a PKI
system, and comprises a public key. Accordingly, identity
certificate 500 comprises standard certificate fields 510 and a
public key field 520. A raw biometric data sample is obtained in
step 530. As discussed above, the biometric data sample is obtained
through any of a wide variety of biometric sensors--including a
fingerprint sensor, a camera for facial imaging, a microphone for
voice records, etc. In some embodiments, all or portions of the raw
biometric data are included in a biometric certificate field. The
raw biometric data sample may then processed for use in a biometric
certificate field. In preferred embodiments, the processing
comprises hashing the sample, as in step 540, or extracting one or
more biometric templates, as in step 550. As discussed above, in
some embodiments of the present invention a hash function is used
to process the data sample and one or more templates are extracted
from the sample. Further, in some embodiments, a plurality of
samples are obtained and processed.
[0066] Biometric templates may then be encrypted for use in a
biometric certificate field, in step 560. Preferred embodiments of
this encrypting step utilize public key 520 to encrypt the
biometric template. In other embodiments, a different key or
procedure is used to encrypt the biometric template. Further, a
template may be encrypted a plurality of times--each with a
different key--for use in a plurality of biometric certificate
fields. The hashed biometric is then included in hashed biometric
certificate field 570. An encrypted template is included in
encrypted biometric template certificate field 580. Other
extensions 590 may be included in final biometrically enhanced
certificate 595.
[0067] In one embodiment, a method for creating a biometrically
enhanced certificate embodied as an X.509 Certificate with Private
Extensions is provided. Such a method is schematically illustrated
in FIG. 5. An enrollment station 119, such as a PDA, mobile phone,
personal computer, or other computing device with an associated
biometric sensor, such as a microphone or fingerprint sensor,
executes a program which collects a raw biometric data sample in
step 200. For example, in this step, a potential user may swipe a
finger across a fingerprint sensor, have an image of the user's
face recorded, or the like, as discussed above.
[0068] The raw biometric data sample is then processed with a
biometric algorithm specific to the type of biometric sensor used
and a biometric template is generated in step 201. In a preferred
embodiment, the sensor is a fingerprint sensor and the algorithm is
a fingerprint minutiae extraction algorithm. Alternatively or in
addition, a hash function could be applied to the biometric data
sample in step 201, generating a has value for use in a biometric
certificate field.
[0069] In step 202, the program collects any required additional
user information such as user name, for entry into field 107 of
identity certificate 101. In other embodiments, further user
information may be collected at this step. In still other
embodiments, step 202 is not required if no further information is
needed. A public/private key pair is generated in step 203. In a
preferred embodiment, the key pair is generated using the RSA
public-key cipher, defined in U.S. Pat. No. 4,405,829
"Cryptographic Communications System and Method (`RSA`)", hereby
incorporated by reference, but others methods such as elliptic
curve ciphers may also be used, such as is set forth in Menezes,
A., Elliptic Curve Public Key Cryptosystems, Kluwer Academic
Publishers, 1993, hereby incorporated by reference.
[0070] The biometric certificate fields (115-118) are then prepared
in step 204 from one or more biometric samples and any biometric
templates according to the above definitions of those fields. The
collected information, including biometric and non-biometric user
information, is sent in step 205 along with the generated public
key to Registration Authority (RA) 120. The RA assembles the
biometric and non-biometric user information into a certificate
request, as known in the art. In a preferred embodiment the
certificate request is in the PKCS#10 format defined in Nystrom, M.
and Kaliski, B., "PKCS #10: Certification Request Syntax
Specification Version 1.7," RFC 2986, November 2000, hereby
incorporated by reference.
[0071] In step 207, RA 120 submits the certificate request to
certificate authority (CA) 121 for signature. CA 121 signs the
certificate in step 208 and returns an X.509 certificate with
biometric fields (a biometrically enhanced certificate) having a
structure generally known in the art--see, for example, ITU-T
Recommendation X.509 (1997 E): Information Technology Open Systems
Interconnection--The Directory: Authentication Framework, June
1997, hereby incorporated by reference.
[0072] CA 121 returns the certificate to RA 120 in step 209. CA 121
may also store a copy of the certificate, or transmit copies to
other entities, but does not do so in a preferred embodiment. RA
120 returns the certificate to the enrollment station in step 210.
RA 120 may also store a copy of the certificate, or transmit copies
to other entities. In a preferred embodiment, RA 120 stores the
certificates in a database.
[0073] Enrollment station 119 stores the certificate with the
public/private key pair, in step 211 leaving a biometrically
enhanced certificate within station 119.
[0074] In other embodiments of the present invention, methods are
provided for creating a biometrically enhanced certificate based on
a base identity certificate and at least one attribute certificate.
In the below described embodiment, it is assumed that the user
already has an X.509 identity certificate and associated
public/private key pair, as discussed above.
[0075] Referring to FIG. 6, which schematically depicts a process
for creating a biometrically enhanced certificate comprising a base
certificate and an attribute certificate, an enrollment station
119, such as a PDA, mobile phone, personal computer, or other
computing device with an associated biometric sensor, such as a
microphone or fingerprint sensor, executes a program, as above,
which collects a biometric sample from a user in step 250.
[0076] The biometric sample is then processed with the biometric
algorithm, as above, specific to the type of biometric sensor used
and a biometric template is generated in step 251. In a preferred
embodiment, the sensor is a fingerprint sensor and the algorithm is
a fingerprint minutiae extraction algorithm.
[0077] The biometric-related fields (115-118) are then prepared in
step 252 from the raw biometric sample and biometric template
according to the above definitions of those fields. The type of
enrollment is known by the enrollment station and is readily
available for inclusion in an enrollment field. The collected
biometric information is put in an attribute certificate request,
an appropriately-specified data structure such as an extensible
markup language (XML) structure, in step 253. Also included is the
content of the "Certificate Serial Number" 103 and/or the "Subject
Name" 107 fields from the user's existing base certificate. In
other embodiments, other or different linking fields from the base
certificate are included.
[0078] The attribute certificate request structure is signed in
step 254 with the user's private key associated with the base
certificate. The signed attribute certificate request is sent in
step 255 to an Attribute Authority (AA) for signature. The AA signs
the attribute certificate in step 256 and returns the certificate
to the enrollment station in step 257. The RA may also store a copy
of the certificate, or transmit copies to other entities. In a
preferred embodiment, the RA stores the certificates in a
database.
[0079] The enrollment station stores the certificate with the base
certificate in step 258, thus completing the process of creating a
biometrically enhanced certificate.
[0080] The methods, certificates, and systems of the present
invention find use in a variety of applications. A first general
use of biometrically enhanced certificates is that of
authentication. That is, a biometrically enhanced certificate may
be used to assert and prove an identity. For example, in an
embodiment in which a biometrically enhanced certificate includes
template 117 encrypted with the public key of a server, that server
may decrypt template 117 with its private key and compare it to a
template extracted from biometric sample data collected from a user
requesting authentication, thus enabling that user to, for example,
log in to a secure web site or other system.
[0081] In an embodiment in which a biometrically enhanced
certificate includes template 116 encrypted with the public key of
a user, the system may require the user to provide a password
releasing his private key, which would then be used to decrypt the
template for comparison to a template extracted from biometric
sample data collected from the user, thus enabling a two-factor
"what you know" and "what you are" authentication, which might
allow a user to, for example, sign a purchase order.
[0082] Biometrically enhanced certificates may also be used for
authorization--that is, determining what a particular user is
allowed to do or see. That is, a server or other device receiving a
biometrically enhanced certificate may correlate the biometrically
enhanced certificate information with specific information that
someone sending that biometrically enhanced certificate may
access--including, but not limited to--financial information
including bank accounts, balances, credit histories, stock
information; purchase information including prices, inventories,
transactions, histories; a vote; or a document request.
[0083] Biometrically enhanced certificates may further be used for
non-repudiation--that is, creating a record of an activity that
will not later be refuted or altered. For example, in an embodiment
in which a biometrically enhanced certificate includes biometric
hash value 115, the hash value of the original biometric sample or
template taken at the time of enrollment and creation of the
biometrically enhanced certificate may be used to prove the
authenticity of a purported biometric sample when that biometric
sample is compared to a biometric sample or template collected at
the time of a particular transaction being repudiated, in order to
prove that the person who enrolled is the same person who was
authenticated for the transaction being repudiated.
[0084] The invention may advantageously implement the methods and
procedures described herein on a general purpose or special purpose
computing device, such as a device having a processor for executing
computer program code instructions and a memory coupled to the
processor for storing data and/or commands. It will be appreciated
that the computing device may be a single computer or a plurality
of networked computers and that the several procedures associated
with implementing the methods and procedures described herein may
be implemented on one or a plurality of computing devices. In some
embodiments the inventive procedures and methods are implemented on
standard server-client network infrastructures with the inventive
features added on top of such infrastructure or compatible
therewith.
[0085] The foregoing descriptions of specific embodiments and best
mode of the present invention have been presented for purposes of
illustration and description. They are not intended to be
exhaustive or to limit the invention to the precise forms
disclosed, and obviously many modifications and variations are
possible in light of the above teaching. The embodiments were
chosen and described in order to best explain the principles of the
invention and its practical application, to thereby enable others
skilled in the art to best utilize the invention and various
embodiments with various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto and their
equivalents.
* * * * *