Fingerprinting Long Forgiving Messages

In his 1983 paper, Neal Wagner1 defines a perfect fingerprint to be an identifying fingerprint added to an object in such a way that any alteration to it that makes the fingerprint unrecognizable will also make the object unusable. A perfect fingerprinting scheme for binary data would seem difficult to devise, since it would be possible to discover the fingerprints by comparing different fingerprinted copies of the same piece of data. In this paper we discuss a fingerprinting scheme which, although it does not surmount this problem entirely, at least specifies the number of copies an opponent must obtain in order to erase the fingerprints.