Source: http://www.google.com/patents/US6301659?dq=6,977,809&ei=-AObT5vAOoSgiQL_5qznDg
Timestamp: 2017-10-21 11:34:31
Document Index: 476744937

Matched Legal Cases: ['application No. 60', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 90', 'application No.60']

Patent US6301659 - Tree-based certificate revocation system - Google Patents
A method and system for overcoming the problems associated with certificate revocation lists (CRL's), for example, in a public key infrastructure. The invention uses a tree-based scheme to replace the CRL....http://www.google.com/patents/US6301659?utm_source=gb-gplus-sharePatent US6301659 - Tree-based certificate revocation system
Publication number US6301659 B1
Application number US 08/979,983
Also published as US20020046337
Publication number 08979983, 979983, US 6301659 B1, US 6301659B1, US-B1-6301659, US6301659 B1, US6301659B1
Patent Citations (40), Non-Patent Citations (75), Referenced by (127), Classifications (12), Legal Events (13)
US 6301659 B1
A method and system for overcoming the problems associated with certificate revocation lists (CRL's), for example, in a public key infrastructure. The invention uses a tree-based scheme to replace the CRL.
1. A method for using at least one Merkle tree to authenticate revocation status about a plurality of certificates, comprising:
(a) generating a plurality of values, wherein each of the values indicates that at least one of the certificates has been revoked and wherein for each certificate, there is at least one value indicating status of the certificate;
(b) constructing at least one Merkle tree containing on a plurality of its nodes at least one of the plurality of values indicating whether at least one of the certificates has been revoked; and
(c) authenticating, with a digital signature, a root node of the at least one Merkle tree to provide an authenticated root.
2. A method according to claim 1, wherein the digital signature is verifiable by an end user.
3. A method according to claim 1, wherein the values indicate which certificates have been revoked.
4. A method according to claim 3, wherein the values include a date of revocation for the certificates that have been revoked.
5. A method according to claim 1, wherein the values indicate which certificates are valid.
6. A method according to claim 1, wherein the values include a date of issue for the certificates that have been issued.
7. A method according to claim 1, wherein the values indicate which certificates have been revoked and which certificates are valid.
8. A method according to claim 1, wherein the values indicate which certificates have been revoked and which certificates have been issued.
9. A method according to claim 1, wherein the values indicate which certificates are valid and which certificates have been issued.
10. A method according to claim 1, wherein the values indicate which certificates have been revoked, which certificates are valid, and which certificates have been issued.
11. A method according to claim 1, wherein at least one of the values corresponds to more than one certificate.
12. A method according to claim 11, wherein the values include a date of issue for the certificates that have been issued.
13. A method according to claim 1, wherein certificate information determines locations of the values within the Merkle tree.
14. A method according to claim 1, wherein positions of the values within the Merkle tree provide information about certificates corresponding thereto.
15. A method according to claim 14, wherein the information includes serial numbers for each of the certificates.
16. A method according to claim 1, wherein the values correspond to serial numbers of the certificates.
17. A method according to claim 16, wherein the certificate values correspond to serial numbers of the certificates combined with additional information.
18. A method according to claim 1, wherein the authenticated root contains additional information.
19. A method according to claim 18, wherein the additional information includes date information.
20. A method according to claim 18, wherein the additional information includes an indication of at least one of: revoked, issued, and valid for describing certificate information corresponding to the values of the Merkle tree.
21. A method according to claim 1, wherein the values indicating status of certificates are leaf nodes of the Merkle tree.
22. A method, according to claim 1, further comprising:
introducing dummy items.
23. A method, according to claim 22, wherein the number of dummy items that is introduced plus the number of other items is a power of two.
This application is a continuation of application Ser. No. 08/741,601, filed on Nov. 1, 1996, now abandoned.
Application is based on U.S. provisional patent application No. 60/006,143 filed on Nov. 2, 1995.
The present invention relates generally to secure communications and more particularly to schemes for certificate management.
In many settings, it is necessary to certify certain data, as well as to revoke already issued certificates. For instance, in a Public-Key Infrastructure, (PKI) it is necessary to certify users' public keys.
In a digital signature scheme, each user U chooses a signing key SKu and a matching verification key, PKu. User U uses SKu to compute easily his digital signature of a message m, SIGu(m), while anyone knowing that PKu is U's public key can verify that SIGu(m) is U's signature of m. Finding SIGu(m) without knowing SKu is practically impossible. On the other hand, knowledge of PKu does not give any practical advantage in computing SKu. For this reason, it is in U's interest to keep SKu secret (so that only he can digitally sign for U) and to make PKu as public as possible (so that everyone dealing with U can verify U's digital signatures). At the same time, in a world with millions of users, it is essential in the smooth flow of business and communications to be certain that PKu really is the legitimate key of user U. To this end, users' public keys are “certified.” At the same time it is also necessary to revoke some of the already-issued certificates.
CERTIFICATION AND REVOCATION OF PUBLIC KEYS.
Typically, certificates for users' public keys are produced and revoked by certifying authorities called CA's. A complete public-key infrastructure may involve other authorities (e.g., PCAS) who may also provide similar services (e.g., they may certify the public keys of their CA's). The present inventions can be easily applied to such other authorities. A CA can be considered to be a trusted agent having an already certified (or universally known) public key. To certify that PKu is U's public key, a CA typically digitally signs PKu together with (e.g., concatenating it with) U's name, a certificate serial number, the current date (i.e., the certification or issue date), and an expiration date. (Before certifying U's public key, it is necessary to perform additional steps, such as properly identifying user U. The present invention, however, does not depend on these additional steps). The CA's signature of PKu is then inserted in a Directory and/or given to U himself.
Upon receiving the (alleged) digital signature of user U of a message M, SIGu(M), a recipient R needs to obtain a certificate for PKu. (Indeed, SIGu(M) may be a correct digital signature of M with respect to some public key PKu, but R has no guarantee that PKu is indeed U's public key). Recipient R may obtain this certificate from the Directory, or from his own memory (if he has previously cached it), or from U himself. Having done this, R verifies (1) the correctness of the CA's certificate for PKu with respect to the CA's public key, and (2) the correctness of SIGu(M) with respect to PKu. (If the CA's public key is not universally known, or cached with R, then a certificate for this key too must be obtained.)
Certificate retrieval is thus possible, although not necessarily cheap. Unfortunately, however, this is not the only retrieval that R needs to do. Indeed, it is crucially important that R makes sure that the certificate for PKu has not been revoked. This check, of course, may not be needed after the certificate's expiration date, but is needed during the certificate's alleged lifetime. A user's certificate can be revoked for a variety of reasons, including key compromise and the fact that the user is no longer associated with a particular CA.
To enable a recipient to establish whether a given certificate has been revoked, it is known that each CA periodically issues and gives the Directory a Certificate Revocation List (CRL for short), in general containing an indication of all the (not yet expired) certificates originally issued by it. A CRL typically consists of the issuer's digital signature of (1) a header comprising the issuer's name (as well as the type of his signature algorithm), the current date, the date of the last update, and the date of the next update, together with (2) a complete list of revoked certificates (whose date has not yet expired), each with its serial number and revocation date. Since it is expected that a CA revokes many of her certificates, a CRL is expected to be quite long.
After performing some checks on the CA's CRL (e.g., checking the CA's digital signature, checking that the CRL has arrived at the expected time, that a certificate declared revoked in the previous CRL of that CA—and not yet expired—still is revoked in the current CRL, etc.), the Directory stores it under its CA name.
When a user queries the Directory about the revocation of a certificate issued by a given CA, the Directory responds by sending to the user the latest CRL of that CA. The user can then check the CRL signature, the CRL dates (so as to receive a reasonable assurance that he is dealing with the latest one), and whether or not the certificate of interest to him belongs to it.
While CRLs are quite effective in helping users establishing which certificates are no longer deemed valid, they are also extremely expensive, because they tend to be very long and need to be transmitted very often.
The National Institute of Standards and Technology has tasked the MITRE Corporation to study the organization and cost of a PKI for the Federal Government. This study estimates that CRLs constitute by far the largest entry in the Federal PKI's cost list. According to MITRES's estimates/assumptions, in the Federal PKI there are about three million users, each CA serves 30,000 users, 10% of the certificates are revoked (5% because of key compromise and 5% because of change in affiliation with the organization connected to a given CA). CRLs are sent out bi-weekly, and, finally, the recipient of a digital signature requests certificate information 20% of the time. (The remaining 80% of the time he will be dealing with public keys in his cache). The study envisages that each revoked certificate is specified in a CRL by means of about 9 bytes: 20 bits of serial number and 48 bits of revocation date. Thus, in the Federal PKI, each CRL is expected to comprise thousands of certificate serial numbers and their revocation dates; the header, however, has a fixed length, consisting of just 51 bytes.
At 2 cents per kilobyte, the impact of CRL transmission on the estimated yearly costs of running the Federal PKI is stunning: if each federal employee verifies 100 digital signatures per day on average, then the total PKI yearly costs are $10,848 Millions, of which $10,237 Millions are due to CRL transmission. If each employee is assumed to verify just 5 digital signatures a day on average, then the total PKI yearly costs are $732 Millions, of which 563 Millions are due to CRL transmission.
The MITRE study thus suggests that any effort should be made to find alternative and cheaper CRL designs. This is indeed the goal of the present invention.
To avoid the dramatic CRL costs, a novel Certification Revocation System is described, where requesting users no longer receive the latest list of revoked certificates (of a given CA). The scheme utilizes a known tree-based authentication technique in a novel way to overcome the problems associated with the prior art.
It is thus a primary object of this invention to provide certificate management without providing CRL's to a user requesting information about the certificate (e.g, its validity). Although special CRL's still may be used between CA's and the Directory in this scheme, the tree-based technique allows the Directory to convince users of whether or not a given certificate is still valid in a way that is essentially individualized, and thus quite convenient.
A known scheme for authenticating an item in a list of items is described in U.S. Pat. No. 4,309,569 to Merkle, and the disclosure therein is hereby incorporated by reference. Familiarity with the Merkle scheme is assumed in the following discussion.
By way of brief background, assume that the set S of certificates consists of n items, where, for convenience, n is a power to two: n=2k (else, we may introduce “dummy” items so that this is the case). The set organizer sorts (e.g., lexicographically) the items in S and then tree-hashes them as taught by Merkle. That is, let H be a one-way hash function, mapping strings of any length into B-bit strings (e.g., B=200). Then conceptually, the organizer stores the ith item, Ii, into the ith leaf of a full binary tree with n leaves. Then, he fills the remaining nodes of the tree in a bottom-up fashion, by storing in every internal node the hash of the concatenation of the content of its two children. In order to develop a minimum of terminology, let N be an internal node where the left child is L and the right child is R, and let VL be the value stored in L and VR the value stored in R (we shall refer to VL and VR as, respectively, a left-value and a right-value). Then, the organizer stores in node N the B-bit value H(VLVR).
In one embodiment of the invention it is assumed that there are two (2) distinct trees (or more precisely, “tree-hashes”), a first tree in which information about issued but non-revoked certificates is stored, and a second tree in which information about revoked certificates is stored. Thus, for example, if the system has had 30,000 certificates issued but 3,000 of these have been revoked, the first tree would include information about the 27,000 certificates that remain valid while the second tree would store the information about the 3,000 revoked certificates. Thus, in this embodiment there is a tree-hash for the non-revoked certificates and a separate tree-hash for the revoked ones. In such case, the root values of these trees may be digitally signed by a CA (together with other information deemed proper) either separately or together; and the Directory uses the first tree to prove to a user that a given certificate is still deemed valid, and the second tree to prove that a certificate has been revoked. The CA builds both trees so that a given certificate (serial number) does not belong to both, but the Directory can also check for this property. Again, this and other operations may be facilitated if the serial number or any representation of the certificate that is deemed proper are ordered when inserted in the tree leaves. Among the various representations of a certificate, of course, one may use the certificate itself.
While the above technique is advantageous, in the preferred embodiment each leaf of the tree-hash stores the serial number of an issued and not-yet-expired certificate, together with an additional bit indicating whether or not the corresponding certificate is no longer valid (i.e., it has been revoked), and, if so, the revocation date. Of course, additional information can be stored about each or some of the serial numbers (e.g., certification date, etc.). Also, some of this information (e.g., the revocation date) can be removed or changed, and some other way of referring to a certificate can be used rather than the serial number, although within the scope of the present invention.
Thus in this case the same tree-hash is used to represent the set of issued and not-yet-expired certificates as well as the set of revoked (not-yet-expired) certificates.
In either embodiment, a problem may arise when the user queries the Directory with a serial number not corresponding to any issued certificate. (Indeed, while many times the user has already seen a certificate and accesses the Directory just to confirm the current validity of that certificate, at other times the user wishes to obtain the corresponding certificate from the Directory). If the corresponding certificate “does not exist,” the Directory is at a loss to proceed. If the Directory responds truthfully, it may not be believed by the user. If the Directory gives the users all the certificates in its possession (or those relative to a given CA) the user may suspect that the Directory left out the certificate of interest. This problem exists as well in a CRL-based system. Indeed, even if the Directory gives the user all possible tree-based information or just the latest CRL of a given CA, this does not prove to the user that the certificate in question does not exist. (In fact, the actions of the Directory may actually be interpreted as saying that the certificate is valid because it does not appear to have been revoked.) Thus in this thorny situation the Directory would have to be trusted.
To rectify this problem, it is desired to have the Directory digitally sign that the certificate specified by the user is not among the existing or the not-yet-expired ones. This scheme at least may prevent frivolous answers by putting some liability on the Directory. Better yet, it is preferred that a CA periodically give the Directory a tree-hash specification of the status of all possible serial numbers at that time. For instance, because it is envisioned that a serial number consists of bits, the CA stores these serial numbers in the leaves of a depth-20 (full) tree-hash, together with an additional bit: 0 if not-yet-expired corresponding certificate exists, and 1 otherwise. After completing the hashing, the CA will digitally sign the root value (alone, or together with the root values of some other tree-hash). This enables the Directory to prove to the user that a serial number does not correspond to any issued and not-yet-expired certificate, namely, by giving the user the digital signature of the root value of this last tree-hash, and then the content of the leaf containing the serial number (or other specification) and the content of the siblings of the path from that leaf to the root.
Just like in the preferred embodiment of the underlying tree-hash scheme itself, one may have two separate trees for this purpose: one tree-hashing the serial numbers of issued and not-yet-expired certificates, and the other tree-hashing the serial numbers not corresponding to issued and not-yet-expired certificates. Of course, one may wish instead to merge together all possible tree-hashes mentioned so far (and possibly others) by having a CA generate a single tree-hash with 220 leaves (i.e., with as many leaves as possible serial numbers), where each leaf stores the corresponding serial number, together with information specifying whether that serial number has been allocated or not, and, if so, whether its certificate has been revoked or not, and possibly other information (e.g, in case of revocation, the revocation date).
It should be appreciated that the above envisions each leaf corresponding to a serial number for simplicity only. For instance if all the information deemed appropriate about a serial number is no more than 80 bits, each leaf may deal with two serial numbers, provided of course that the information is properly coded so as not to generate confusions, errors or ambiguity. Smaller tree hashes may be built this way.
It should further be realized this type of digital signature allows batch processing. Namely, rather than signing n quantities separately, a signer tree-hashes them so as to obtain a single root-value, and then digitally signs this root-value (together with additional quantities if desired) when requested to give the signature of quantity i, the signer gives his digital signature of the root, and then the content of leaf i, and the content of the sibling of the party from that leaf to the root. This is a way to substitute n individual signatures (that can be expensive to obtain) with just one signature and n−1 hashing (which are not expensive at all). Notice that the signer does not need to be the one who supplies individualized signatures; if he transfers the n quantities (or the entire tree hash) together with his signature of the root to someone else, he may supply the signatures on demand. Notice that any signature scheme can be used for the root, including pen-written signatures, rather than digital ones.
The foregoing has outlined some of the more pertinent objects and details of a preferred embodiment of the present invention. These objects and details should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention as will be described. Those skilled in the art will recognize that the invention can be practiced, with modification, in other and different certification methods and schemes within the spirit and scope of the invention.
One of the preferred implementations of the various routines disclosed above is as a set of instructions in a code module resident in the random access memory of a computer. Until required by the computer, the set of instructions may be stored in another computer memory, for example, in a hard disk drive, or in a removable memory such as an optical disk (for eventual use in a CD ROM) or floppy disk (for eventual use in a floppy disk drive). In addition, although the various methods described are conveniently implemented in a general purpose computer selectively activated or reconfigured by software, one of ordinary skill in the art would also recognize that such methods may be carried out in hardware, in firmware, or in more specialized apparatus constructed to perform the required method steps.
While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is to be limited only by the following claim(s).
US4881264 * Jul 30, 1987 Nov 14, 1989 Merkle Ralph C Digital signature system and method based on a conventional encryption function
US5231666 * Apr 20, 1992 Jul 27, 1993 International Business Machines Corporation Cryptographic method for updating financial records
US5432852 * Sep 29, 1993 Jul 11, 1995 Leighton; Frank T. Large provably fast and secure digital signature schemes based on secure hash functions
US5434919 * Jan 11, 1994 Jul 18, 1995 Chaum; David Compact endorsement signature systems
1 "Final Text of Draft Amendments DAM 4 to ISO/IEC 9594-2, DAM 2 to ISO/IEC 9594-6, DAM 1 to ISO/IEC 9594-7, and DAM 1 to ISO/IEC 9594-8 on Certificate Extensions," Jun. 30, 1996, 41 pages.
2 "Public Key Infrastructure Study-Final Report," National Institute of Standards and Technology, Apr. 1994.
3 "Public Key Infrastructure Study—Final Report," National Institute of Standards and Technology, Apr. 1994.
4 A Dictionary of Modern Legal Usage, Oxford University Press 1987, p. 930.
5 ANSI X9.55-199X "Public Key Cryptography for the Financial Services Industry: Extensions to Public Key Certificates and Certificate Revocation Lists," (working draft), Jul. 3, 1996, 37 pages.
6 ANSI x9.57-199x "Public Key Cryptography for the Financial Services Industry: Certificate Management," (working draft), Jun. 21, 1996, 86 pages.
7 Bellare, M., et al., "Incremental Cryptology: The Case of Hashing and Signing," Proceedings of Crypto '95, 1995, pp. 216-233.
8 Burr, W.E., "Public Key Infrastructure (PKI) Technical Specifications (Version 1): Part C-Concept of Operations," Published on the World Wide Web, Feb. 12, 1996, 30 pages.
9 Burr, W.E., "Public Key Infrastructure (PKI) Technical Specifications (Version 1): Part C—Concept of Operations," Published on the World Wide Web, Feb. 12, 1996, 30 pages.
10 Burr, William E. et al., "A Proposed Federal PKI Using X.509 V3 Certificates," Published on the World Wide Web.
11 Burr, William, "A Proposed Federal PKI Using X. 509 V3 Certificates: The NISSC Presentation," Published on the World Wide Web.
12 Burr, William, et al., "MISPC: Minimum Interoperability Specifications for PKI Components," Published on the World Wide Web, Dec. 2, 1996.
13 Chaum, D., "Untraceable Electronic Mail, Return Addresses, and Digital Pseudonyms," Communications of the ACM, vol. 24, No. 2, Feb. 1981, pp. 84-88.
14 Chokhani, Santosh, "Security Considerations in Using X. 509 Certificates," Published on the World Wide Web.
15 Chokhani, Santosh, et al., "Certificate Policy and Certification Practice Statement Framework", Published on the World Wide Web, Nov. 3, 1996.
16 CygnaCom Solutions, Inc., "Federal Public Key Infrastructure (PKI) Technical Specifications Part D-Interoperability Profiles, "Published on the World Wide Web, Sep. 27, 1995, 91 pages.
17 CygnaCom Solutions, Inc., "Federal Public Key Infrastructure (PKI) Technical Specifications Part D—Interoperability Profiles, "Published on the World Wide Web, Sep. 27, 1995, 91 pages.
18 Dodson, Donna F., "NIST PKI Implementation Projects," Published on the World Wide Web.
19 Elgamal, et al., Securing Communications on the Intranet and Over the Internet, Netscape Communications Corporation, Jul. 1996.
20 Escrowed Encryption Standard (EES) FIPS Pub. 185, Feb. 9, 1994.
21 Facsimile message from Chini Krishnan of Integris Security, Inc. to Professor Silvio Micali dated Feb. 17, 1997, 7 pages including cover sheet, submitted in attached sealed envelope as Proprietary Material Not Open to Public. To be Opened Only by Examiner of Other Authorized Patent and Trademark Office Employee.
22 Facsimile message from Chini Krishnan of Integris Security, Inc. to Professor Silvio Micali, dated Feb. 25, 1997, 12 pages including cover sheet submitted in attached sealed envelope as Proprietary Material Not Open to Public. To be Opened Only by Examiner or Other Authorized Patent and Trademark Office Employee.
23 Farrell, S., et al., "Internet Public Key Infrastructure Part III: Certificate Management Protocols," Published on the World Wide Web, Dec. 1996, 83 printed pages.
24 Farrell, S., et al., "Internet Public Key Infrastructure Part III: Certificate Management Protocols," Published on the World Wide Web, Jun. 1996, pp. 1-36.
25 Ford, Warwick, "A Public Key Infrastructure for U.S. Government Unclassified but Sensitive Operations," Published on the World Wide Web, Sep. 1, 1995, 93 pages.
26 Ford, Warwick, "Public-Key Infrastructure Standards," Published on the World Wide Web, Oct. 1996, 15 printed pages.
27 Gennaro, Rosario et al., "Robust Threshold DSS Signatures," Abstract from EuroCrypt '96.
28 Harn, L., "Group Oriented (t,n) threshold digital signature scheme and digital multisignature," IEE Proc.-Comput. Digit. Tech., vol. 141, No. 5, Sep. 1994, pp. 307-313.
29 Housley, R., et al., "Internet Public Key Infrastructure Part I: X.509 Certificate and CRL Profile," Jun. 1996, Published on the World Wide Web, pp. 1-30.
30 International Search Report from PCT/US 96/17374, dated Feb. 19, 1997, 7 pages.
31 International Standard ISO/IEC 9594-8, "Information Technology-Open Systems Interconnection-The Directory: Authentication Framework," ISO/IEC, second edition, Sep. 15, 1996.
32 International Standard ISO/IEC 9594-8, "Information Technology—Open Systems Interconnection—The Directory: Authentication Framework," ISO/IEC, second edition, Sep. 15, 1996.
33 Kent et al., "Privacy Enhancement for Internet Electronic Mail: Part II-Certificate-Based Key Management," IAB Task Force, Request for Comments No. 114, Aug. 1989, pp. 1-22.
34 Kent et al., "Privacy Enhancement for Internet Electronic Mail: Part II—Certificate-Based Key Management," IAB Task Force, Request for Comments No. 114, Aug. 1989, pp. 1-22.
35 Lamport, L., "Password Authentication with Insecure Communication," Communications of the ACM, Nov. 1981, pp. 770-772.
36 Linn, J., "Privacy Enhancement for Internet Electronic Mail: Part I-Message Encipherment and Authentication Procedures," IAB Privacy Task Force, Request for Comments No. 113, Aug. 1989, pp. 1-30.
37 Linn, J., "Privacy Enhancement for Internet Electronic Mail: Part I—Message Encipherment and Authentication Procedures," IAB Privacy Task Force, Request for Comments No. 113, Aug. 1989, pp. 1-30.
38 Menezes et al, "Handbook fo Applied Cryptography." (C)1997. pp 566, 576, 577, 588, 589, 706, 716, 720, 728, 729, 737, 751.*
39 Menezes et al, "Handbook fo Applied Cryptography." ©1997. pp 566, 576, 577, 588, 589, 706, 716, 720, 728, 729, 737, 751.*
40 Micali, S. et al., "An Efficient Zero-Knowledge Method for Answering Is He In or Out?," Abstract, presented by M. Rabin at the National Computer Science Institute in Berkeley, CA, Dec. 1995.
41 Micali, S., "Computationally-Sound Proofs," Apr. 11, 1995, MIT Laboratory for Computer Science, 55 pages.
42 Micali, Silvio, "Enhanced Certificate Revocation System," Technical Report, Nov. 1995.
43 Nazario, N., "Federal Public Key Infrastructure (PKI) Version 1 Technical Specifications: Part B-Technical Security Policy, "Published on the World Wide Web, Mar. 13, 1996, 20 pages.
44 Nazario, N., "Federal Public Key Infrastructure (PKI) Version 1 Technical Specifications: Part B—Technical Security Policy, "Published on the World Wide Web, Mar. 13, 1996, 20 pages.
45 Nazario, Noel A., "Security Policies for the Federal Public Key Infrastructure," Published on the World Wide Web, Oct. 24, 1996.
46 Nazario, Noel et al., "Management Model for the Federal Public Key Infrastructure," Published on the World Wide Web, Oct. 24, 1996.
47 One page e-mail message from Dr. Micali to Integris dated Mar. 4, 1997, regarding references AR and AS.
48 One page reply e-mail message from Integris to Dr. Micali dated Mar. 5, 1997, confirming confidential status of references AR and AS.
49 Polk, W., editor, "Federal Public Key Infrastructure (PKI) Technical Specifications (Version 1) Part A: Requirements," Published on the World Wide Web, Dec. 6, 1996, 18 pages.
50 Polk, William T., "Minimum Interoperability Specifications for PKI Components," Published on the World Wide Web, Nov., 1996.
51 Rivest, et al., "A Method for Obtaining Digital Signatures and Public-Key Cryptosystems," Communications of the ACM, Feb. 1978, pp. 120-126.
52 Rivest, et al., "PayWord and MicroMint: Two Simple Micropayment Schemes," Nov. 7, 1995, MIT Laboratory for Computer Science/Weizmann Institute of Science, 11 pages.
53 Rivest, Ronald et al., "SDSI-A Simple Distributed Security Infrastructure," Sep. 15, 1996, Published on the World Wide Web.
54 Rivest, Ronald et al., "SDSI—A Simple Distributed Security Infrastructure," Sep. 15, 1996, Published on the World Wide Web.
55 The Digital Distributed System Security Architecture, Proceedings of the 12th National Computer Security Conference, 1989, pp. 305-319.
56 Toward a national public key infrastructure, IEEE Communications Magazine, Sep. 1994, vol. 32, No. 9, ISSN 0163-6804, pp. 70-74.
57 Two page e-mail message from Dr. Micali to Integris dated Mar. 4, 1997, mentioning references AR and AS.
58 U.A. application No. 08/729,619, Micali, filed Oct. 11, 1996.
59 U.S. application No. 08/559,533, Micali, S., filed Nov. 16, 1995.
60 U.S. application No. 08/608,134, Micali, filed Feb. 28, 1996.
61 U.S. application No. 08/636,854, Micali, filed Apr. 23, 1996.
62 U.S. application No. 08/648,344, Micali, filed May 15, 1996.
63 U.S. application No. 08/649,905, Micali, filed May 15, 1996.
64 U.S. application No. 08/715,712, Micali, S., filed Sep. 19, 1996.
65 U.S. application No. 08/728,675, Micali, S., filed Oct. 10, 1996.
66 U.S. application No. 08/746,007, Micali, S., filed Nov. 5, 1996.
67 U.S. application No. 08/753,589, Micali, filed Nov. 26, 1996.
68 U.S. application No. 08/756,720, Micali, filed Nov. 26, 1996.
69 U.S. application No. 08/763,536, Micali, filed Dec. 9, 1996.
70 U.S. application No. 60/.033,415, Micali, Dec. 18, 1996.
71 U.S. application No. 60/004,796, Micali, S., filed Oct. 2, 1995.
72 U.S. application No. 60/006,038, Micali, filed Oct. 24, 1995.
73 U.S. application No. 60/025,128, Micali, S., files Aug. 29, 1996.
74 U.S. application No. 90/004215, Micali, filed Apr. 10, 1996.
75 U.S. application No.60/024,786, Micali, S., filed Sep. 10, 1996.
US6748531 * Mar 28, 2000 Jun 8, 2004 Koninklijke Philips Electronics N.V Method and apparatus for confirming and revoking trust in a multi-level content distribution system
US6853988 Sep 20, 2000 Feb 8, 2005 Security First Corporation Cryptographic server with provisions for interoperability between cryptographic systems
US7120793 Sep 26, 2002 Oct 10, 2006 Globalcerts, Lc System and method for electronic certificate revocation
US7143165 Oct 18, 2004 Nov 28, 2006 Microsoft Corporation Updating trusted root certificates on a client computer
US7240194 Mar 22, 2002 Jul 3, 2007 Microsoft Corporation Systems and methods for distributing trusted certification authorities
US7266692 Dec 15, 2005 Sep 4, 2007 Ntt Docomo, Inc. Use of modular roots to perform authentication including, but not limited to, authentication of validity of digital certificates
US7315941 Dec 14, 2005 Jan 1, 2008 Ntt Docomo Inc. Multi-certificate revocation using encrypted proof data for proving certificate's validity or invalidity
US7373503 * Apr 21, 2003 May 13, 2008 Matsushita Electric Industrial Co., Ltd. Public key certificate revocation list generation apparatus, revocation judgement apparatus, and authentication system
US7584351 * Jan 7, 2005 Sep 1, 2009 Ricoh Company, Ltd. Method of transferring digital certificate,apparatus for transferring digital certificate, and system, program, and recording medium for transferring digital certificate
US7657751 * May 13, 2004 Feb 2, 2010 Corestreet, Ltd. Efficient and secure data currentness systems
US7743252 Jun 16, 2006 Jun 22, 2010 Ntt Docomo, Inc. Use of modular roots to perform authentication including, but not limited to, authentication of validity of digital certificates
US7747857 Jun 16, 2006 Jun 29, 2010 Ntt Docomo, Inc. Use of modular roots to perform authentication including, but not limited to, authentication of validity of digital certificates
US7814314 Aug 31, 2005 Oct 12, 2010 Ntt Docomo, Inc. Revocation of cryptographic digital certificates
US7840994 Sep 9, 2004 Nov 23, 2010 Ntt Docomo, Inc. Method and apparatus for efficient certificate revocation
US8006086 Jun 26, 2009 Aug 23, 2011 Ntt Docomo, Inc. Revocation of cryptographic digital certificates
US8024562 Jun 26, 2009 Sep 20, 2011 Ntt Docomo, Inc. Revocation of cryptographic digital certificates
US8099603 May 21, 2007 Jan 17, 2012 Corestreet, Ltd. Secure ID checking
US8156327 Jun 26, 2009 Apr 10, 2012 Ntt Docomo, Inc. Revocation of cryptographic digital certificates
US8209531 Jun 26, 2009 Jun 26, 2012 Ntt Docomo, Inc. Revocation of cryptographic digital certificates
US8321664 Jun 29, 2009 Nov 27, 2012 Ntt Docomo, Inc. Method and apparatus for efficient certificate revocation
US9425967 * Mar 20, 2013 Aug 23, 2016 Industrial Technology Research Institute Method for certificate generation and revocation with privacy preservation
US9733849 Nov 23, 2015 Aug 15, 2017 Security First Corp. Gateway for cloud-based secure storage
US20030217265 * Apr 21, 2003 Nov 20, 2003 Toshihisa Nakano Public key certificate revocation list generation apparatus, revocation judgement apparatus, and authentication system
US20040064691 * Sep 26, 2002 Apr 1, 2004 International Business Machines Corporation Method and system for processing certificate revocation lists in an authorization system
US20050080899 * Oct 18, 2004 Apr 14, 2005 Microsoft Corporation Updating trusted root certificates on a client computer
US20050204164 * Jan 7, 2005 Sep 15, 2005 Hiroshi Kakii Method of transferring digital certificate,apparatus for transferring digital certificate, and system, program, and recording medium for transferring digital certificate
US20060059333 * Aug 31, 2005 Mar 16, 2006 Gentry Craig B Revocation of cryptographic digital certificates
US20060129803 * Sep 9, 2004 Jun 15, 2006 Gentry Craig B Method and apparatus for efficient certificate revocation
US20060129827 * Dec 12, 2005 Jun 15, 2006 Samsung Electronics Co., Ltd. Method of revoking public key of content provider
US20060137006 * Dec 15, 2005 Jun 22, 2006 Ramzan Zulfikar A Use of modular roots to perform authentication including, but not limited to, authentication of validity of digital certificates
US20070150744 * Dec 22, 2005 Jun 28, 2007 Cheng Siu L Dual authentications utilizing secure token chains
US20080016370 * May 21, 2007 Jan 17, 2008 Phil Libin Secure ID checking
US20080232590 * Jan 23, 2004 Sep 25, 2008 Rivest Ronald L Micropayment Processing Method and System
US20080244263 * Mar 29, 2007 Oct 2, 2008 Tc Trust Center, Gmbh Certificate management system
US20090265547 * Jun 26, 2009 Oct 22, 2009 Gentry Craig B Revocation of cryptographic digital certificates
US20090265548 * Jun 26, 2009 Oct 22, 2009 Gentry Craig B Revocation of cryptographic digital certificates
US20100005292 * Jun 29, 2009 Jan 7, 2010 Gentry Craig B Method and apparatus for efficient certificate revocation
US20100153714 * Feb 25, 2010 Jun 17, 2010 Zulfikar Amin Ramzan Use of modular roots to perform authentication including, but not limited to, authentication of validity of digital certificates
US20100174904 * Feb 25, 2010 Jul 8, 2010 Ntt Docomo, Inc. Use of modular roots to perform authentication including, but not limited to, authentication of validity of digital certificates
US20100287370 * Jul 21, 2010 Nov 11, 2010 Gentry Craig B Revocation of cryptographic digital certificates
US20140289512 * Mar 20, 2013 Sep 25, 2014 Industrial Technology Research Institute Method for certificate generation and revocation with privacy preservation
U.S. Classification 713/158, 713/157
International Classification H04L9/32, G06Q20/00
Cooperative Classification H04L9/3268, H04L2209/38, H04L2209/30, H04L9/3236, H04L2209/60, G06Q20/02
European Classification G06Q20/02, H04L9/32T
Apr 27, 2005 SULP Surcharge for late payment
Apr 27, 2005 FPAY Fee payment