What are fingerprints?

[Werner Koch]

 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