Symmetric ciphers as hash functions

[Arash Partow]

Hi all,

How does one properly use a symmetric cipher as a cryptographic hash
function? I seem to be going around in circles.

Initially I thought you choose some known key and encrypt the data
with the key, using either the encrypted text or the internal state of
the cipher as the hash value, turns out all one needs to do to break
it, is decrypt the hash value with the "known" key and you get a value
which will produce the same hash value.

Reversing the situation (using the data as the key and a known plain-
text) makes a plaintext attack seem like a joy etc..

Are there any papers/books/etc that explain the implementation/use of
symmetric ciphers (particularly AES) as cryptographic hash functions?

btw I know that hash functions and symmetric ciphers share the same
structural heritage (feistel rounds etc...), I just don't seem to be
making the usage link at this point in time... :D

Any help would be very much appreciated.



Kind regards


Arash Partow
________________________________________________________
Be one who knows what they don't know,
Instead of being one who knows not what they don't know,
Thinking they know everything about all things.
http://www.partow.net


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