Deutschetelekom Ag

Johannes Ueberberg

Joerg Schwenk

A method for identifying betrayers of proprietary data which enables a betrayer, i.e., an authorized subscriber who has disclosed one of his partial keys to a third person without authorization, to be unequivocally identified. A respective subset of encryption keys is assigned to each authorized subscriber according to finite geometric structures and methods such that the necessary characteristic of the k-resilience used for identifying a betrayer is guaranteed. A betrayer search algorithm is used for the unequivocal identification of a betrayer. Coalitions of betrayers may also be unequivocally identified.

Method for identifying betrayers of proprietary data

In a method for embedding collusion-secure digital fingerprints in electronic documents, using a geometric order system one point in the projective space PG (d, q) is unambiguously assigned to each flagging position in a document via a secret function. At least two hyperplanes of PG (d, q) are assigned to each fingerprint, each being exclusively assigned to one fingerprint only, and for each fingerprint precisely those flagging positions that correspond to the points of the selected hyperplane are flagged. To trace attempts to delete fingerprints, an intersection of hyperplanes is reconstructed from the flagged flagging positions that have been found in the document, by analyzing linear dependencies the hyperplanes are determined, and by calculating these hyperplanes the fingerprints of colluding customers may be determined.

Method for embedding manipulation-secure digital fingerprints into electronic documents

The present method concerns inserting manipulation-proof digital fingerprints into electronic documents making it possible to detect manipulations by purchasers or groups of purchasers. According to the present invention based on a predefined number of copies and a maximum number of copying hackers per document, a location or an area for the digital fingerprint of the customer is defined for each copy. All the locations or areas defined in the document for digital fingerprints are subject in their totality to an enclosed finite geometric ordering system, in which intersections of the digital fingerprints occur at defined locations or areas. By analyzing the intersection points not found by the hackers, the hackers involved in the manipulation can be uniquely determined. The method described is suitable, in particular, for identifying copies of documents which are subject to copyright protection.

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St. Augustin, Germany

Johannes Ueberberg