Method and system for recovering the validity of cryptographically signed digital data

• US 7,694,126 B2
• Filed: 08/08/2005
• Issued: 04/06/2010
• Est. Priority Date: 10/22/1999
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Miyazaki, Kunihiko, Matsuki, Takeshi, Takaragi, Kazuo, Toyoshima, Hisashi, Susaki, Seiichi, Sasaki, Ryoichi, Yoshiura, Hiroshi
• Primary Examiner(s): JUNG, DAVID YIUK
• Application Number:
  US11/199,615
• Publication Number:
  US 20060059357A1
• Time in Patent Office: 1,702 Days
• Field of Search: 713/150, 713/151, 713/153, 713/168
• US Class Current: 713/150
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: G06F 21/645 using a third party
• CPC Class Codes: G06F 2221/2101 Auditing as a secondary aspect
• CPC Class Codes: G06Q 20/3825 Use of electronic signatures
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/12 Applying verification of the received information cryptographic mechanisms or cryptographic arrangements for data integrity or data verification H04L9/32
• CPC Class Codes: H04L 9/3252 using DSA or related signature schemes, e.g. elliptic based signatures, ElGamal or Schnorr schemes
• CPC Class Codes: H04L 9/50 using hash chains, e.g. blockchains or hash trees

Abstract

According to the present invention, techniques, including a method and system, for restoring and/or validating data and/or associated signature log entries are provided. One embodiment of the present invention provides a method for validating a restored message, having an entry generated in a signature log for a message, where the entry includes cryptographic information associated with the message. Next, when said message is lost, the restored message is generated responsive to a request; and the restored message is validated using the signature log. In another embodiment a method for validating a selected log entry by using a signature log having a plurality of recorded log entries is provided. The method includes: computing a cryptographic value for the selected log entry; and determining if the cryptographic value is part of another recorded log entry.

Claims

1. A method for verifying a first log entry for a corresponding first message included in a first log comprising a plurality of log entries, wherein each log entry includes a hash value (H_msg) determined from a message corresponding to said each entry, wherein said each log entry further includes a hash value (H_log) determined from a previous log entry, wherein said each log entry further includes a signature value determined from the hash values H_msg and H_log, wherein one or more log entries among log entries P_l to P_k are checkpointed, the method comprising operating a computer to perform steps of:

receiving information for a log entry P_j having a corresponding message M_j;

determining an index m, where l≧

m≧

k and m>

j;

determining a hash value H by applying a hashing function on log entries P_j to P<sub>m−

1</sub>;

judging whether the hash value H is equal to a hash value associated with a subsequent log entry; and

outputting a result of the judging step.

2. The method of claim 1 wherein each of the one or more log entries among the log entries P_l,to P_k that are checkpointed is publicly accessible.

3. The method of claim 2 wherein said each of the one or more log entries is publicly accessible over a mass media server.

4. The method of claim 1 wherein each checkpointed log entry is registered by an eligibility public establishment or a private notary.

5. The method of claim 1 wherein for each checkpointed log entry, data or a hash value of the data is included in a second log different from the first log, and the data includes a signature value associated with said each checkpointed log entry.

6. A method for verifying a log entry for a message included in a first log, wherein each log entry P_i in the first log includes a hash value (H_msg) of a message corresponding to P_i, a hash value (H_log)of a previous log entry, and a signature value based H_msg and H_log, wherein one or more log entries among log entries P_l to P_k are checkpointed, the method comprising operating a computer to perform steps of:

receiving information for a first log entry P_j having a corresponding message M_j;

receiving information for a second log entry P_l having a corresponding message M_l where l>

j;

determining a hash value H by applying a hashing function on log entries P_j to P<sub>l−

1</sub>;

judging whether the hash value H is equal to a hash value associated with a subsequent log entry; and

outputting a result of the judging step.

7. The method of claim 6 further comprising checking whether the log entry P_l is a checkpointed log entry.

8. The method of claim 6 wherein each of the one or more log entries among the log entries P_l to P_k that are checkpointed is publicly accessible.

9. The method of claim 8 wherein said each of the one or more log entries is publicly accessible over a mass media server.

10. The method of claim 6 wherein each checkpointed log entry is registered by an eligibility public establishment or a private notary.

11. The method of claim 6 wherein for each checkpointed log entry, data or a hash value of the data is included in a second log different from the first log, and the data includes a signature value associated with said each checkpointed log entry.