What are fingerprints?

Werner Koch wk@gnupg.org
Mon, 13 Dec 1999 10:32:25 +0100

 On Sun, Dec 12, 1999 at 11:26:05AM -0700
 Dale Harris wrote:

> are using the correct key. Obviously if there is a fingerprint match, or you
> want to be absolutely sure, then you'll want to check the entire key.
A fingerprint is the output of a cryptographic hash function (hash digest); therefore you have to assume that it is unique - most cryptograpic protocols rely on the properties of these hash algorithms (MD5, SHA1, RIPME-MD 160). The most important one is that these functions are collision-free, which means that it is hard (in the sense of it is hard to factor the product of 2 large primes) to produce two different data images which yields the same fingerprint. It really makes sense to call it a fingerprint, as this is the counterpart in the non technical area. Hash algorithms are a basic building block in cryptography, more information may be found at http://www.esat.kuleuven.ac.be/~bosselae/ -- Werner Koch at guug.de www.gnupg.org keyid 621CC013