Message digest

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With Message Digest ( MD , in German about: news-summary ) is a group of cryptographic protocols called. They are one-way hash functions . These functions appear with the claim that they - with a reasonable effort - cannot be reversed and no collision can be calculated. This means that it should not be possible to restore the original text for a cipher (irreversible). It should also not be possible to calculate a text that generates the same cipher as the original text (collision-free).

Various hash functions

  • MD2 : a Ron Rivest developmentreleased in 1988. It generates a 128 bit hash value. A cryptographic attack was successfully carried out under simplified assumptions, so that its use was advised against as early as 1995.
  • MD4 : The use of this function is generally not recommended.
  • MD5 : was also developed by Ron Rivest to replace MD4 . In the meantime, collisions have also been calculated for this, so that MD5 is also considered unsafe.

The fact that collisions can be computed does not automatically render these hash functions worthless. MD5 is probably still acceptable for generating one-time passwords, MD4 should no longer be used under any circumstances.