Re: what is a hash ?

From: aditya (truman_at_rediffmail.com)
Date: 06/25/03 

Date: 24 Jun 2003 21:45:03 -0700

>
> No. A hash is NOT a one way encryption, unless the word encryption has
> had its definition broadened so much it loses all meaning. Even if
> Schneier says it.
>
> It shares with encryption the feature that the output depends on the
> input, and that from the output it should is hard to figure out what the
> input was. A cryptgraphic hash also has the property that even if you
> know one input that produces the output it should be hard to find a
> different one. (of course in encryption it is impossible since in an
> encryption, every output has a unique input).
>
>
>
> An encryption can be used as a key element in a hash and a hash can be
> used as a key element in encryption, but they are really totally
> different beasts.
>
> ]and about the most popular algorithms. I am talking about algorithms
> ]used in computing digital signatures. Thats what Hash functions are
> ]primarily used for.
>
> No, hashes are primarily used in lookup tables. cryptographic hashes are
> often used in digital signatures, yes, and that is probably the main use
> of cryptographic hashes. However, even non-cryptographic hashes are
> often used to detect changes in the input. Almost all error correcting
> schemes are based on hashes, in which however it should be easy to
> figure out from the output of the hash what changed in the input. (Ie,
> every CD you play is chock full of hashes to do the error correction.)

Alright. I did not know hash functions are used apart from purposes of
authentication. Thanks for correcting me. I am new to this field and
plan to continue my work further.

regards

Aditya

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