Asymmetric Fingerprinting ( Extended

Fingerprinting schemes deter people from illegal copying of digital data by enabling the merchant of the data to identify the original buyer of a copy that was redistributed illegally. All known fingerprinting schemes are symmetric in the following sense: Both the buyer and the merchant know the fingerprinted copy. Thus, when the merchant finds this copy somewhere, there is no proof that it was the buyer who put it there, and not the merchant. We introduce asymmetric fingerprinting, where only the buyer knows the fingerprinted copy, and the merchant, upon finding it somewhere, can find out and prove to third parties whose copy it was. We present a detailed definition of this concept and constructions. The first construction is based on a quite general symmetric fingerprinting scheme and general cryptographic primitives; it is provably secure if all these underlying schemes are. We also present more specific and more efficient constructions.