Treyfer

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Treyfer

Designer(s):	Gideon Yuval
First published:	1997
Key size(s):	64 bits
Block size(s):	64 bits
Rounds:	32
Best public cryptanalysis:
A slide attack using 232 known plaintexts and 244 work succeeds for any number of rounds

In cryptography, Treyfer is a block cipher/MAC designed in 1997 by Gideon Yuval. Aimed at smart card applications, the algorithm is extremely simple and compact; it can be implemented in just 29 bytes of code.

Treyfer has a rather small key size and block size of 64 bits each. All operations are byte-oriented, and there is a single 8×8-bit S-box. The S-box is left undefined; the implementation can simply use whatever data is available in memory. In each round, each byte has added to it the S-box value of the sum of a key byte and the previous data byte, then it is rotated left one bit. The design attempts to compensate for the simplicity of this round transformation by using a large number of rounds: 32.

Due to the simplicity of its key schedule, using the same 8 key bytes in each round, Treyfer was one of the first ciphers shown to be susceptible to a slide attack. This cryptanalysis, which is independent of the number of rounds and the choice of S-box, requires 2³² known plaintexts and 2⁴⁴ computation time.

[edit] References

• David Wagner, Alex Biryukov (1999). "Slide Attacks" (PostScript). Retrieved on 2007-01-25.