DIGITAL SIGNATURE SERVER AND USER TERMINAL

• US 20130132728A1
• Filed: 11/25/2009
• Published: 05/23/2013
• Est. Priority Date: 11/25/2009
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Suu, Hiroshi, Miura, Akira, Kasahara, Akihiro, Matsukawa, Shinichi
• Granted Patent: US 8,887,153 B2
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: H04L 63/0457 wherein the sending and receiving network entities apply dynamic encryption, e.g. stream encryption cryptographic mechanisms or cryptographic arrangements for stream encryption H04L9/065
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/14 using a plurality of keys or algorithms
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

To reduce a load on a user terminal imposed when verifying signature data and at the same time reduce a load on a server, a signature key matrix KM includes a plurality of signature keys Ki-j arranged in a matrix structure of m rows and n columns, and is stored in a signature key matrix database 21. A correspondence relationship between a signature key set CK which is an aggregate of any signature keys selected from the n columns respectively and a user terminal 30 is stored in a correspondence relationship information database 22. A signature data generating unit 24 generates signature data having a matrix structure by encrypting a content digest D generated based on content data C by n number of signature keys included in the signature key matrix KM.

Claims

1. A signature data server operative to generate signature data indicating that content data is a certified one, comprising:

a signature key column set database configured to store a signature key column set which is an aggregate of signature key columns each of which is an aggregate of a plurality of signature keys;

a correspondence relationship information database configured to store correspondence relationship information indicating a correspondence relationship between a signature key set and a user terminal, the signature key set being an aggregate of any signature keys selected from the signature key columns respectively; and

a signature data generating unit configured to generate signature data by encrypting a content digest by using the plurality of signature keys included in the signature key column set, the content digest being generated based on the content data.

2. The signature data server according to claim 1, further comprising a sending/receiving control unit configured to send the signature data to a content server for providing content data to the user terminal and receive the content digest from the content server.

3. The signature data server according to claim 1, further comprising a signature data key generating unit configured to generate a plurality of different signature data keys corresponding to a plurality of columns of the signature data respectively,

wherein in each of the plurality of columns, the signature data generating unit encrypts the signature data key corresponding to that column by using the signature keys.

4. The signature data server according to claim 3,

wherein in a first column of the signature data, the signature data generating unit encrypts the content digest and the signature data key corresponding to the first column by using the signature keys, whereas in a j-th column (j≧

2) of the signature data, the signature data generating unit generates encrypted data by encrypting the content digest and the signature data key corresponding to the j-th column by using the signature data key corresponding to a (j−

1)th column, and further encrypts the encrypted data by using the signature keys.

5. The signature data server according to claim 1,

wherein the signature data generating unit encrypts a verification value used for verifying the signature data by the signature data key.

6. A user terminal operative to receive, together with content data, signature data indicating that the content data is a certified one, comprising:

a content data/signature data receiving unit configured to receive from outside, together with the content data, signature data generated by encrypting a content digest by a plurality of signature keys included in a signature key column set which is an aggregate of signature key columns each including a plurality of signature keys, the content digest being generated based on the content data;

a signature key set receiving unit configured to receive from outside, a signature key set which is an aggregate of the signature keys selected one by one from the signature key columns of the signature key column set respectively; and

a signature data verifying unit configured to verify the signature data by decrypting the content digest included in the signature data by using the signature keys included in the signature key set, and then comparing this content digest with a content digest obtained from the content data received from outside.

7. The user terminal according to claim 6,

wherein the signature data includes a plurality of columns in each of which a signature data key different from signature data keys for the other columns is encrypted by the signature keys.

8. The user terminal according to claim 7,

wherein in a first column of the signature data, the content digest and the signature data key for the first column are encrypted by using the signature keys, whereas in a j-th column (j≧

2) of the signature data, encrypted data generated by encrypting the content digest and the signature data key for the j-th column by using the signature data key for a (j−

1)th column is encrypted by using the signature keys, and

the signature data verifying unit decrypts the content digest and the signature data key in the first column of the signature data by using the signature keys, and then decrypts the content digest and the signature data key in the j-th column (j≧

2) of the signature data by using the signature data key for the (j−

1)th column and the signature keys.