One-way compression function: Difference between revisions

Revision as of 22:37, 5 January 2018

Revision as of 22:42, 5 January 2018

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But, in some cases it is easier because a single implementation of a block cipher can be used for both block cipher and a hash function. It can also save [[machine code|code]] space in very tiny [[embedded system]]s like for instance [[smart card]]s or [[Electronic control unit|nodes in cars]] or other machines.

Therefore, the hash-rate or rate gives a glimpse of the efficiency of a hash function based on a certain compression function. The rate of an iterated hash function outlines the ratio between the number of block cipher operations and the output. More precisely, if n denotes the output bit-length of the block cipher the rate represents the ratio between the number of processed bits of input m, n output bits and the necessary block cipher operations s to produce these n output bits. Generally, the usage of lessfewer block cipher operations could result in a better overall performance of the entire hash function but it also leads to a smaller hash-value which could be undesirable. The rate is expressed inby the formula <math>R_h=\frac{\left|m_i\right|}{s\cdot n}</math>.

The hash function can only be considered secure if at least the following conditions are met: