Construction of Davies-Meyer

A construction of Davies-Meyer (or function of Davies-Meyer) is a technique used in the functions of cryptographic chopping.

It consists in carrying out a XOR between the exit of the function of compression and the exit of preceding compression.

Resistance

With a construction of this type, it is easy to find a point fixed for any block $M~$ coming from the message. If one forces $E\; (M,\; H\_i)\; ~$ with zero, and that one finds a manner of reversing $E$ under this constraint then one can pose the following relation: $F\; (M,\; H\_\; \{i+1\})\; =\; E\; (M,\; H\_i)\; \backslash \; oplus\; H\_i\; =\; H\_i$ because $0\; \backslash \; oplus\; H\; =\; H$. In 1999, Drew Dean develops in its thesis an attack based on this property. Thanks to this vulnerability which makes it possible to find Préimage S, the functions of chopping based on Davies-Meyer are less robust.

Related articles

• Construction of Merkle-Damgård
• Construction of Miyaguchi-Preneel
• Construction of Matyas-Meyer-Oseas

More

• Thesis of Bart Van Rompay about the cryptographic functions of chopping
• Chapter 9 of '' Handbook off Applied Cryptography ''

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