Re: [Haskell-cafe] Digests

2010/12/3 Permjacov Evgeniy :

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The data integrity checks is well-known problem. A common soluting is use of 'checksums'. Most of them , however, are built in quite obfuscated manner (like md5) that results in ugly and error-prone implementations (see reference implementation for same md5).

So, the question is: is there a checksum, that is easy to implement over stream of bytes and may work as good checksum and is good in sence that creation of messages with same checksum that given message has is very hard problem (at least 2^128 tries) ? 2^128 tries needed for hash size of 256 bits. See http://en.wikipedia.org/wiki/Birthday_attack Ok, I have to use at least 256 bit resulting value. This is four Word64 or 32 Word8 ... Well, maybe it will work Most of the time you can get away with usual block ciphers (and even with weaker parameters). There is a scheme that transforms block cipher into hash function: http://en.wikipedia.org/wiki/CRHF#Hash_functions_based_on_block_ciphers */me wrote it into to_read list. The problem is, however, that block ciphers are quite unfriendly to plain word8 streams. It is not a deadly

On 12/03/2010 12:33 AM, Serguey Zefirov wrote: problem, but i'd like to avoid block collections.

RC5, for example, parametrized by number of encryption rounds. RC5 with 12 rounds has sufficiently good avalanche (spread of bit change) so that you can use 12-round RC-5 instead of full death proof 20-round.