Re: New hash contest by NIST, similair to AES competition

"Alan" <alan@xxxxxxxxxx> writes:

Symmetric block ciphers can be used in various ways to produce a
message digest:

http://en.wikipedia.org/wiki/Hash_functions_based_on_block_ciphers

Is there a drawback to that approach (other than wanting more diversity
in the toolbox)?

To quote from that same article.

"Using a block cipher as a hash function is usually much slower than using
a specially designed hash function. This is because all known secure
constructions do the key scheduling for each block of the message. It has
been shown that without repeated key scheduling it is impossible to
construct a secure block cipher based hash function[1]. In practice
reasonable speeds are achieved provided the key scheduling of the selected
block cipher is not a too heavy operation"


If diversity is the issue, wouldn't it be equally beneficial to come up
with new block ciphers? That way you improve diversity both of hash
functions and block ciphers.

.

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