Code generating method and unit thereof, code detecting method and unit thereof, and watermark embedding unit and watermark detecting unit

• US 6,901,515 B1
• Filed: 09/08/2000
• Issued: 05/31/2005
• Est. Priority Date: 09/30/1999
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Muratani, Hirofumi
• Primary Examiner(s): Barrón, Gilberto
• Assistant Examiner(s): GURSHMAN, GRIGORY
• Application Number:
  US09/658,565
• Time in Patent Office: 1,726 Days
• Field of Search: 713/176, 713/200
• US Class Current: 713/176
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0063 in relation to collusion attacks, e.g. collusion attack resistant
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• CPC Class Codes: H04H 2201/50 characterised by the use of watermarks
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 2201/3226 of identification information or the like, e.g. ID code, index, title, part of an image, reduced-size image
• CPC Class Codes: H04N 2201/3236 Details of authentication information generation
• CPC Class Codes: H04N 2201/324 Selecting a particular authentication information from amongst a plurality of different authentication information
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes

Abstract

Residue calculating sections respectively obtain residues which take a plurality of integers as modulus, with respect to a user ID. The plurality of integers are stored in modulus storage sections and are prime to each other. Based on these residues and parameters stored in a coding parameter storage section, component codes constructed by continuous sequences of 1 and 0 using a predetermined number of bits as a unit are respectively generated by component code generating sections. These component codes are concatenated by a concatenating section, thereby to obtain a code to be embedded, which constructs watermark information.

Claims

1. A method for generating a computer readable code to be embedded in a predetermined content, comprising the steps of:

calculating a plurality of residues, taking a plurality of integers which are relatively prime to each other, as moduli, with respect to a user identification number of a user who uses the content;

generating a plurality of computer readable component codes respectively expressing the residues obtained in the residue calculating step; and

concatenating the computer readable component codes generated in the computer readable component code generating step, thereby to generate the computer readable code to be embedded.

2. A unit for generating a computer readable code to be embedded in a predetermined content, comprising:

residue calculating means for calculating a plurality of residues, taking a plurality of integers which are relatively prime to each other, as moduli, with respect to a user identification number of a user who uses the content;

computer readable component code generating means for generating a plurality of computer readable component codes respectively expressing the residues obtained by the residue calculating means; and

concatenating means for concatenating the computer readable component codes generated by the computer readable component code generating means, thereby to generate the computer readable code to be embedded.

3. A unit according to claim 2, wherein the component code generating means generates, as the plurality of component codes, codes each constructed by continuous sequences of 1 and 0, taking a predetermined number of bits as a unit.

9. A unit according to claim 2, further comprising user identification number assigning means for selecting one candidate that is erroneously detected as the user identification number of a colluder at a smaller possibility, among a plurality of user candidate number candidates, in response to an assigning request for the user identification number, and for assigning the selected user identification number to user specifying data which specifies the user.

10. A unit according to claim 9, wherein the user identification number assigning means inputs sequentially the plurality of user identification number candidates one after another, determines whether the possibility at which each of the candidates is erroneously detected as the user identification number of the colluder is high or low, and assigns a candidate to the user specifying data at a time point when a user identification number candidate having the possibility is determined to be low is inputted.

11. A unit according to claim 9, wherein the user identification number assigning means includes storage means which stores a plurality of user identification numbers having a lower possibility at which the plurality of user identification numbers are erroneously detected as the user identification numbers of the colluder, and selects and reads a user identification number to be assigned to the user specifying data from the user identification numbers stored in the storage means.

12. A watermark embedding unit for embedding a code to be embedded, which is generated by the unit according to claim 2, as watermark information into the content.

13. A computer readable storage medium which stores a content in which a computer readable code to be embedded, which is generated by the unit according to claim 2, is embedded.

4. A unit for generating a computer readable code to be embedded, comprising:

calculating means for calculating a set of a plurality of integral elements in correspondence with an inputted user identification number;

computer readable component code generating means for generating computer readable component codes respectively in correspondence with the integral elements, such that among k′

computer readable component codes capable of expressing all sets of integral elements that are calculated by the calculating means with respect to a predetermined number of user identification numbers, k combinations of the k′

computer readable component codes can uniquely express the user identification numbers; and

concatenating means for concatenating the computer readable component codes generated by the computer readable component code generating means, thereby to generate a computer readable code to be embedded, wherein

k′

is determined to be c(k+l)/q or more where c is a positive integer of 3 or more, l is a positive integer, and q is a number of the integral elements which can be detected from each of the computer readable component codes when detecting the computer readable embedded code.

5. A unit according to claim, 4, wherein, where p_i(i=1, 2, . . . , k′

) is a number of values which each of the integral elements calculated by the calculating means can take with respect to the predetermined number of user identification numbers and where ε

is a detection error rate which is assumed when detecting the code to be embedded, k′

is determined such that a condition of ${\left[1-\underset{i=1}{\overset{l}{\prod <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left\{1-{\left(1-\frac{1}{p_i}\right)}^c\right\}\right]}^{c<br><br>\left(k+l\right)/2^{C_{k+l^{\times <br><br>2^{k+l}}}}}\ge <br><br>1-\frac{\mathrm{\varepsilon <br><br>}}{2}$

is satisfied.

6. A unit according to claim 4, wherein the calculating means calculates a set of residues, which take a plurality of integers relatively prime to each other as moduli, as the set of integral elements, in correspondence with the inputted user identification number.

7. A unit according to claim 4, wherein the calculating means calculates a set of numbers of elements, which belong to an equivalence class defined by a parallel transformation, as the set of integral elements, in correspondence with the inputted user identification number.

8. A unit according to claim 4, wherein the calculating means calculates a set of numbers of elements, which belong to an equivalence class defined by a parallel transformation, as the set of integral elements, in correspondence with the inputted user identification number, and

where p_i (i=1, 2, . . . , k′

) is one same positive integer p, a condition of $k^{\mathrm{\prime <br><br>}}=\frac{c}{2}<br><br>\left(k+l\right)\le <br><br>\frac{p^k-1}{p-1}$

is further satisfied.