Dynamic tardos traitor tracing schemes
AssigneeIrdeto B.V.
InventorsPeter Roelse, Jeroen Doumen, Thijs Laarhoven
Life of this patent
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Abstract
A fingerprinting method. For each round in a series of rounds: providing to each receiver in a set of receivers a version of a source item of content, the source item of content corresponding to the round. For the round there is a corresponding part of a fingerprint-code for the receiver, the part includes one or more symbols. The version provided to the receiver represents those one or more symbols. One or more corresponding symbols are obtained from a suspect item as a corresponding part of a suspect-code. For each receiver in the set of receivers, a corresponding score that indicates a likelihood that the receiver is a colluding-receiver is updated.
Claims18
A fingerprinting method comprising, for each round in a series of rounds:
- providing to each receiver in a set of receivers a version of a source item of content, the source item of content corresponding to the round, wherein for the round there is a corresponding part of a fingerprint-code for the receiver, the part comprising one or more symbols, wherein the version provided to the receiver represents those one or more symbols;
- obtaining, from a suspect item of content one or more corresponding symbols as a corresponding part of a suspect-code;
- for each receiver in the set of receivers, updating a corresponding score that indicates a likelihood that the receiver is a colluding-receiver, wherein a colluding-receiver is a receiver that has been provided with a version of a source item of content that has been used to generate a suspect item of content, wherein said updating is based on the fingerprint-code for the receiver and the suspect-code;
- for each receiver in the set of receivers, if the score for the receiver exceeds a threshold, updating the set of receivers by removing the receiver from the set of receivers so that the receiver is not provided with a further version of a source item of content, wherein the threshold is set such that the probability that a receiver that is not a colluding-receiver has a score exceeding the threshold is at most a predetermined probability.
The method of any one of the preceding claims, in which either:
- (a) the method comprises generating a fingerprint-code for a receiver in advance of the series of rounds;
- or
- (b) said providing comprises generating the part of the fingerprint-code for the receiver.
The method of any one of the preceding claims, in which the version of the source item of content provided to a receiver is formed by watermarking a copy of the source item of content with the part of the fingerprint-code for the receiver.
An apparatus comprising a processor arranged to carry out a fingerprinting method, wherein the method comprises, for each round in a series of rounds:
- providing to each receiver in a set of receivers a version of a source item of content, the source item of content corresponding to the round, wherein for the round there is a corresponding part of a fingerprint-code for the receiver, the part comprising one or more symbols, wherein the version provided to the receiver represents those one or more symbols;
- obtaining, from a suspect item of content one or more corresponding symbols as a corresponding part of a suspect-code;
- for each receiver in the set of receivers, updating a corresponding score that indicates a likelihood that the receiver is a colluding-receiver, wherein a colluding-receiver is a receiver that has been provided with a version of a source item of content that has been used to generate a suspect item of content, wherein said updating is based on the fingerprint-code for the receiver and the suspect-code;
- for each receiver in the set of receivers, if the score for the receiver exceeds a threshold, updating the set of receivers by removing the receiver from the set of receivers so that the receiver is not provided with a further version of a source item of content, wherein the threshold is set such that the probability that a receiver that is not a colluding-receiver has a score exceeding the threshold is at most a predetermined probability.
A computer program which, when executed by a processor, causes the processor to carry out a fingerprinting method comprising, for each round in a series of rounds:
- providing to each receiver in a set of receivers a version of a source item of content, the source item of content corresponding to the round, wherein for the round there is a corresponding part of a fingerprint-code for the receiver, the part comprising one or more symbols, wherein the version provided to the receiver represents those one or more symbols;
- obtaining, from a suspect item of content one or more corresponding symbols as a corresponding part of a suspect-code;
- for each receiver in the set of receivers, updating a corresponding score that indicates a likelihood that the receiver is a colluding-receiver, wherein a colluding-receiver is a receiver that has been provided with a version of a source item of content that has been used to generate a suspect item of content, wherein said updating is based on the fingerprint-code for the receiver and the suspect-code;
- for each receiver in the set of receivers, if the score for the receiver exceeds a threshold, updating the set of receivers by removing the receiver from the set of receivers so that the receiver is not provided with a further version of a source item of content, wherein the threshold is set such that the probability that a receiver that is not a colluding-receiver has a score exceeding the threshold is at most a predetermined probability.
Dependencies are inferred from the claim text.