One-way compression function: Difference between revisions

Revision as of 03:56, 15 February 2006

Revision as of 15:27, 22 February 2006

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A hash function must be able to process an arbitrary-length message into a fixed-length output. This can be achieved by breaking the input up into a series of equal-sized blocks, and operating on them in sequence using a ''compression function''. The compression function can either be specially designed for hashing or be built from a block cipher.

<div align=center>[[Image:Merkle-Damgard hash.svgpng|Merkle-Damgård hash function schematic. ''g'' represents the finalization function.]]</div>

The last block processed should also be [[Padding (cryptography)|length padded]], this is crucial to the security of this construction. This construction is called the ''[[Merkle-Damgård construction]]''. Most widely used hash functions, including [[SHA-1]] and [[MD5]], take this form.