Information processing method and information processing apparatus

• US 20040003261A1
• Filed: 06/20/2003
• Published: 01/01/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Hayashi, Junichi
• Granted Patent: US 7,167,988 B2
• Time in Patent Office: Days
• US Class Current: 713/187
• CPC Class Codes: H04L 2209/30 Compression, e.g. Merkle-Damgard construction
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04N 1/32101 Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
• CPC Class Codes: H04N 2201/3235 Checking or certification of the authentication information, e.g. by comparison with data stored independently
• CPC Class Codes: H04N 2201/3236 Details of authentication information generation

Abstract

A code stream and data indicating a normalization method are inputted to a normalization processing unit 21, and the normalization processing unit applies normalization processing to the code stream to generate a normalized code stream. Next, when signature data is inputted, a verification processing unit 22 performs encryption and decryption processing with respect to the signature data using a public key Kp and calculates a Hash value (first Hash value) and, on the other hand, calculates a Hash value of the normalized code stream (second Hash value). Next, the verification processing unit compares the first Hash value and the second Hash value and, if the first Hash value and the second Hash value are equal, judges that the code stream is not falsified. On the other hand, if the first Hash value and the second Hash value are not equal, the verification processing unit judges that the code stream is falsified.

Claims

1. An information processing method performed by a verification device which verifies whether or not falsification has been applied to compression-coded data to be outputted from a coding device, comprising:

a holding step of holding verification data which is obtained based upon compression-coded data in a normalized state generated in said coding device;

an input step of inputting compression-coded data, which is obtained by coding coding object data in said coding device, and normalization information, which indicates a reference for converting the compression-coded data into the normalized state, from said coding device;

a normalization step of normalizing the compression-coded data, which is inputted in said input step, using the normalization information;

a first calculation step of calculating a first value based upon the verification data;

a second calculation step of calculating a second value based upon the compression-coded data normalized in said normalization step; and

a determination step of determining whether or not falsification has been applied to the compression-coded data, which is inputted in said input step, according to a result of comparison of the first value and the second value.

2. The information processing method according to claim 1,

wherein coding performed by said coding device is lossless compression coding.

3. The information processing method according to claim 1,

wherein the verification data held in said holding step is data generated based upon compression-coded data, which is obtained by normalizing and compressing coding object data in said coding device, and the data is received from said coding device by said verification device.

4. The information processing method according to claim 1,

wherein the verification data held in said holding step is data generated by converting compression-coded data, which is obtained by normalizing and compressing coding object data in said coding device, into another value and encrypting the value with an encryption key, and the data is received from said coding device by said verification device.

5. The information processing method according to claim 4,

wherein said encryption key is a secret key.

6. The information processing method according to claim 4,

wherein, in said first calculation step, the first value is calculated by decrypting the verification data using a predetermined decryption key.

7. The information processing method according to claim 6,

wherein said decryption key is a secret key.

8. The information processing method according to claim 6,

wherein said decryption key is a public key.

9. The information processing method according to claim 1,

wherein the verification data held in said holding step is data generated by converting compression-coded data, which is obtained by normalizing and compressing coding object data in said coding device, into a Hash value and encrypting the Hash value with an encryption key, and the data is received from said coding device by said verification device.

10. The information processing method according to claim 9,

wherein, in said first calculation step, the first value equivalent to the Hash value is calculated by decrypting the verification data using a predetermined decryption key.

11. The information processing method according to claim 1,

wherein, in said determination step, in the case in which the first value and the second value are not equal, it is determined that falsification has been applied to the compression-coded data inputted in said input step.

13. A program for causing a computer to execute the information processing method according to claim 1.

14. A computer readable storage medium for storing the program according to claim 13.

12. An information processing apparatus for verifying whether or not falsification has been applied to compression-coded data to be outputted from a coding device, comprising:

holding means for holding verification data which is obtained based upon compression-coded data in a normalized state generated in said coding device;

input means for inputting compression-coded data, which is obtained by coding coding object data in said coding device, and normalization information, which indicates a reference for converting the compression-coded data into the normalized state, from said coding device;

normalization means for normalizing the compression-coded data, which is inputted by said input means, using the normalization information;

first calculation means for calculating a first value based upon the verification data;

second calculation means for calculating a second value based upon the compression-coded data normalized by said normalization means; and

determination means for determining whether or not falsification has been applied to the compression-coded data, which is inputted by said input means, according to a result of comparison of the first value and the second value.