Certificate revocation system

• US 20050055548A1
• Filed: 05/13/2004
• Published: 03/10/2005
• Est. Priority Date: 10/24/1995
• Status: Active Grant

• Current Assignee: Assa Abloy AB
• Original Assignee: Silvio Micali
• Inventors: Micali, Silvio
• Granted Patent: US 7,529,928 B2
• Time in Patent Office: Days
• US Class Current: 713/158
• CPC Class Codes: G06Q 20/02 involving a neutral party, e.g. certification authority, notary or trusted third party [TTP]
• CPC Class Codes: G06Q 20/3674 involving authentication
• CPC Class Codes: H04L 9/321 involving a third party or a trusted authority
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3268 using certificate validation, registration, distribution or revocation, e.g. certificate revocation list [CRL]

Abstract

A method of managing certificates in a communication system having a certifying authority and a directory. Preferably, the method begins by having the certifying authority generate certificates by digitally signing a given piece of data. At a later point time, the certifying authority may produce a string that proves whether a particular certificate is currently valid without also proving the validity of at least some other certificates. The technique obviates use of certification revocation lists communicated between the certifying authority and the directory.

Claims

1-23. -23. (Cancelled)

24. A method of conveying information about certificates, comprising:

at every date D of a sequence of dates, having an authority produce a digitally signed certificate revocation status using a single digital signature that provides a positive and explicit statement about the validity status at date D of each not-yet-expired certificate in a plurality of certificates;

providing the digitally signed certificate revocation status to a directory; and

having the directory store the latest received digitally signed certificate revocation status to be provided as a response to an inquiry about revocation status of a particular one of the plurality of certificates.

25. A method, according to claim 24, wherein digitally signing includes digitally signing with respect to a public verification key pk, which is digitally signed by the authority with respect to another public verification key PK.

26. A method, according to claim 25, wherein having pk digitally signed by the authority includes having pk be a quantity within the plurality of certificates and having the authority digitally sign the certificates with respect to PK.

27. A method, according to claim 25, wherein digitally signing with respect to the public verification key pk includes digitally signing using an off-line digital signature scheme.

28. A method, according to claim 24, wherein the certificate revocation status includes a revocation signature indicating certificates that have been revoked together with revocation dates thereof.

29. A method, according to claim 24, wherein the directory is not trusted and can not make a valid certificate revoked and can not make a revoked certificate valid.

30. A method, according to claim 24, wherein each of the plurality of certificates has a serial number.

31. A method, according to claim 30, wherein the plurality of certificates have sequential serial numbers.

32. A method, according to claim 31, wherein the certificate revocation status includes a string having a plurality of bits, each of which corresponds to a particular one of the plurality of certificates and wherein each bit of the string is set to a first value if a corresponding one of the certificates is revoke and set to a second, different, value otherwise.

33. A method of conveying information about certificates, comprising:

having an authority digitally sign, using a first digital signature scheme, the public key pk of a second signature scheme, wherein pk'"'"'s secret key is known to an other entity;

at every date D of a sequence of dates, having the other entity produce a digitally signed certificate revocation status, signed with respect to pk, using a single digital signature that provides a positive and explicit statement about the validity status at date D of each not-yet-expired certificate in a plurality of certificates;

providing the digitally signed certificate revocation status to a directory; and

having the directory store the latest received digitally signed certificate revocation status to be provided as a response to an inquiry about revocation status of a particular one of the plurality of certificates.

34. A method, according to claim 33, wherein having the authority digitally sign pk includes having pk be a quantity within the plurality of certificates and having the authority digitally sign at least one of the plurality of certificates using the first signature scheme.

35. A method, according to claim 33, wherein the certificate revocation status includes a revocation signature indicating certificates that have been revoked together with revocation dates thereof.

36. A method, according to claim 33, wherein the directory is not trusted and can not make a valid certificate revoked and can not make a revoked certificate valid.

37. A method, according to claim 33, wherein each of the plurality of certificates has a serial number.

38. A method, according to claim 37, wherein the plurality of certificates have sequential serial numbers.

39. A method, according to claim 38, wherein the certificate revocation status includes a string having a plurality of bits, each of which corresponds to a particular one of the plurality of certificates and wherein each bit is set to a first value if a corresponding one of the certificates is revoked and set to a second, different, value otherwise.

40. A method of obtaining information about a particular certificate, comprising:

receiving from an other entity a digitally signed certificate revocation status that uses a single digital signature to provide a positive and explicit statement about the validity status of each not-yet-expired certificate in a plurality of certificates at date D in a sequence of dates, wherein the plurality of certificates includes the particular certificate;

confirming that the certificate revocation status has been digitally signed by a trusted entity; and

if the certificate revocation status has been digitally signed by a trusted entity, extracting the information about the particular certificate from the certificate revocation status.

41. A method, according to claim 40, further comprising:

prior to receiving the digitally signed certificate revocation status, sending a message to the other entity requesting information about the particular certificate.

42. A method, according to claim 40, wherein the trusted entity is an authority.

43. A method, according to claim 42, wherein the authority previously issued the particular certificate.

44. A method, according to claim 40, wherein the trusted entity is an entity other than an authority and wherein the certificate revocation status is digitally signed using a key pk relative to a signature scheme that is different from a signature scheme used by the authority.

45. A method, according to claim 44, wherein the authority digitally signs pk;

46. A method, according to claim 40, wherein the certificate revocation status includes a revocation signature indicating certificates that have been revoked together with revocation dates thereof.

47. A method according to claim 40, wherein the other entity is not trusted and can not make a valid certificate revoked and can not make a revoked certificate valid.

48. A method, according to claim 40, wherein each of the plurality of certificates has a serial number.

49. A method, according to claim 48, wherein the plurality of certificates have sequential serial numbers.

50. A method, according to claim 49, wherein the certificate revocation status includes a string having a plurality of bits, each of which corresponds to a particular one of the plurality of certificates and wherein each bit is set to a first value if a corresponding one of the certificates is revoked and set to a second, different, value otherwise.

51. A method of providing information about a particular certificate, comprising:

receiving from an other entity a digitally signed certificate revocation status that uses a single digital signature to provide a positive and explicit statement about the validity status of each not-yet-expired certificate in a plurality of certificates at date D in a sequence of dates, wherein the plurality of certificates includes the particular certificate; and

providing the digitally signed certificate revocation status to a user.

52. A method, according to claim 51, further comprising:

prior to providing the digitally signed certificate revocation status, receiving a message from the user requesting information about the particular certificate.

53. A method, according to claim 51, wherein the certificate revocation status is digitally signed by an authority.

54. A method, according to claim 53, wherein the authority previously issued the particular certificate.

55. A method, according to claim 51, wherein the certificate revocation status is digitally signed by an entity other than an authority using a key pk relative to a signature scheme that is different from a signature scheme used by the authority.

56. A method, according to claim 55, wherein the authority digitally signs pk;

57. A method according to claim 51, wherein the certificate revocation status includes a revocation signature indicating certificates that have been revoked together with revocation dates thereof.

58. A method, according to claim 51, wherein each of the plurality of certificates has a serial number.

59. A method, according to claim 58, wherein the plurality of certificates have sequential serial numbers.

60. A method, according to claim 59, wherein the certificate revocation status includes a string having a plurality of bits, each of which corresponds to a particular one of the plurality of certificates and wherein each bit is set to a first value if a corresponding one of the certificates is revoked and set to a second, different, value otherwise.