[ILUG] hashing algorithm

[Justin Mason]

Caolan McNamara said:

> We talking at cross purposes here, just to be clear on everything, SHA1 
> (Secure Hash Algorithm) is a hashing algorithm. They are not intended to 
> encrypt something, just to generate a fixed len chunk of data that uniquely 
> identifys it. Theres no way back from their hash, theres often a use for 
> them in encryption software but something like crypt is not a hashing 
> algorithm and neither is technology like SSL.

Just to drift slightly OT in the traditional manner: actually, hash algos
can be used to encrypt, just fine.  Schneier's Applied Cryptography goes
into some details (18.11, _One Way Hash Functions Using Symmetric Block
Algorithms_).

To illustrate: UNIX crypt(3) uses DES, which is indeed a encryption
algorithm, but it's used as a hash in UNIX passwd files.

--j.