Digital watermarking system using a cryptographic key

• US 20050193206A1
• Filed: 02/17/2005
• Published: 09/01/2005
• Est. Priority Date: 02/17/2004
• Status: Abandoned Application

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Inoue, Yasuaki, Kunisa, Akiomi
• Application Number:
  US11/059,316
• Publication Number:
  US 20050193206A1
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: H04L 2209/608 Watermarking
• CPC Class Codes: H04L 9/3247 involving digital signatures
• 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 2201/3281 Encryption; Ciphering

Abstract

A watermark embedder embeds a cryptographic key as a digital watermark into input host data and thereby generates key-embedded host data, and then provides it to a hash generator and a signature attacher. A hash generator generates a hash by putting the key-embedded host data into a one-way function, and provides the hash to an encryptor. The encryptor encrypts hash generated by the hash generator with the cryptographic key and thereby generates a digital signature. The signature attacher attaches the digital signature generated by the encryptor to the key-embedded host data generated by the watermark embedder, and outputs the signature-attached key-embedded host data.

Claims

1. A digital watermark embedding apparatus comprising:

an encrypting unit which encrypts additional data to be attached to original data;

a watermark embedding unit which embeds a cryptographic key necessary for decrypting the encrypted additional data into the original data as a digital watermark; and

an attaching unit which attaches the encrypted additional data to the original data.

2. A digital watermark embedding apparatus comprising:

an encrypting unit which encrypts data briefly representing a characteristic of original data so as to generate a digital signature;

a watermark embedding unit which embeds a cryptographic key necessary for decrypting the digital signature into the original data as a digital watermark; and

a signature attaching unit which attaches the digital signature to the original data.

3. The apparatus of claim 2 further comprising a generating unit which generates the data briefly representing the characteristic of the original data by putting the original data into a one-way function.

4. A digital watermark extracting apparatus comprising:

a detaching unit which takes original data and additional data separately out of input data;

a watermark extracting unit which extracts a cryptographic key which has been embedded as a digital watermark into the original data; and

a decrypting unit which decrypts the additional data with the cryptographic key.

5. A digital watermark extracting apparatus comprising:

a signature detaching unit which takes original data and a digital signature separately out of signature-attached data;

a watermark extracting unit which extracts a cryptographic key which has been embedded as a digital watermark into the original data; and

a decrypting unit which decrypts the digital signature with the cryptographic key.

6. The apparatus of claim 5 further comprising:

a generating unit which generates data briefly representing a characteristic of the original data by putting the original data into a one-way function; and

a comparing unit which compares the digital signature decrypted by the decrypting unit with the data briefly representing the characteristic of the original data generated by the generating unit.

7. A digital watermark extracting apparatus comprising:

a signature detaching unit which takes original data and a digital signature separately out of signature-attached data;

a watermark extracting unit which extracts a cryptographic key which has been embedded as a digital watermark into the original data;

an encrypting unit which encrypts data briefly representing a characteristic of the original data with the cryptographic key so as to generate a digital signature for verification; and

a comparing unit which compares the digital signature taken out by the signature detaching unit with the digital signature for the verification generated by the encrypting unit.

8. A digital watermark embedding apparatus comprising:

an encrypting unit which encrypts data briefly representing a characteristic of each original data in a series of input original data so as to generate a digital signature;

a watermark embedding unit which embeds a cryptographic key necessary for decrypting the digital signature into the original data as a digital watermark;

a signature attaching unit which attaches the digital signature to the original data; and

a holding unit which holds the digital signature generated by the encrypting unit,

wherein the encrypting unit generates the digital signature for the original data currently processed in such a manner that the generated digital signature depends on the digital signature for the original data formerly processed which has been held in the holding unit.

9. The apparatus of claim 8, wherein the encrypting unit generates the digital signature by using a different cryptographic key for the each original data.

10. A digital watermark embedding apparatus comprising:

an encrypting unit which encrypts data briefly representing a characteristic of each original data in a series of input original data so as to generate a digital signature;

a watermark embedding unit which embeds a cryptographic key necessary for decrypting the digital signature into the original data as a digital watermark;

a signature attaching unit which attaches the digital signature to the original data;

a first holding unit which holds the digital signature generated by the encrypting unit; and

a second holding unit which holds the original data in which the digital watermark has been embedded by the watermark embedding unit,

wherein the encrypting unit generates the digital signature for the original data currently processed in such a manner that the generated digital signature depends on the digital signature for the original data formerly processed which has been held in the first holding unit, and the signature attaching unit attaches the digital signature generated for the original data currently processed to the original data formerly processed which has been held in the second holding unit.

11. The apparatus of claim 10, wherein the encrypting unit generates the digital signature by using a different cryptographic key for the each original data.

12. A digital watermark extracting apparatus comprising:

a signature detaching unit which receives a series of input signature-attached data and takes original data and a digital signature separately out of each signature-attached data;

a watermark extracting unit which extracts a cryptographic key that has been embedded as a digital watermark into the original data;

a decrypting unit which decrypts the digital signature, which has been taken out by the signature detaching unit, with the cryptographic key;

a generating unit which generates data briefly representing a characteristic of the original data by putting the original data into a one-way function; and

a holding unit which holds the digital signature taken out by the signature detaching unit,

wherein the generating unit generates the data briefly representing the original data currently processed in such a manner that the generated data depends on the digital signature for the original data formerly processed which has been held in the holding unit.

13. A digital watermark extracting apparatus comprising:

a signature detaching unit which receives a series of input signature-attached data and takes original data and a digital signature separately out of each signature-attached data;

a watermark extracting unit which extracts a cryptographic key that has been embedded as a digital watermark into the original data;

an encrypting unit which encrypts data briefly representing a characteristic of the original data with a cryptographic key so as to generate a digital signature for verification;

a comparing unit which compares the digital signature taken out by the signature detaching unit with the digital signature for the verification generated by the encrypting unit; and

a holding unit which holds the digital signature taken out by the signature detaching unit,

wherein the encrypting unit generates the digital signature for the verification for the original data currently processed in such a manner that the generated digital signature depends on the digital signature for the original data formerly processed which has been held in the holding unit.

14. A data structure of a self-decryptable type of data comprising original data with a header attached thereto, wherein the header of the original data contains a digital signature obtained by encrypting data briefly representing a characteristic of the original data, and a cryptographic key necessary for decrypting the digital signature is embedded as a digital watermark into the original data.

15. A data structure of a self-decryptable type of data comprising original data, wherein a digital signature obtained by encrypting data briefly representing a characteristic of the original data and a cryptographic key necessary for decrypting the digital signature are embedded as a double watermark into the original data.

16. A digital watermark embedding method comprising attaching to the original data a digital signature obtained by encrypting data briefly representing a characteristic of original data, and embedding a cryptographic key necessary for decrypting the digital signature into the original data as a digital watermark.

17. A digital watermark extracting method comprising extracting a cryptographic key which has been embedded as a digital watermark into original data, and decrypting a digital signature attached to the original data with the cryptographic key so as to verify the digital signature.