In
cryptography
Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...
, Treyfer is a
block cipher
In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called ''blocks''. Block ciphers are specified cryptographic primitive, elementary components in the design of many cryptographic protocols and ...
/
MAC designed in 1997 by Gideon Yuval. Aimed at
smart card
A smart card, chip card, or integrated circuit card (ICC or IC card) is a physical electronic authentication device, used to control access to a resource. It is typically a plastic credit card-sized card with an embedded integrated circuit (IC) c ...
applications, the algorithm is extremely simple and compact; it can be implemented in just 29 bytes of
8051
The Intel MCS-51 (commonly termed 8051) is a single chip microcontroller (MCU) series developed by Intel in 1980 for use in embedded systems. The architect of the Intel MCS-51 instruction set was John H. Wharton. Intel's original versions were po ...
machine code
In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...
.
Treyfer has a rather small
key size
In cryptography, key size, key length, or key space refer to the number of bits in a key used by a cryptographic algorithm (such as a cipher).
Key length defines the upper-bound on an algorithm's security (i.e. a logarithmic measure of the fastest ...
and
block size of 64 bits each. All operations are byte-oriented, and there is a single 8×8-bit
S-box
In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext, thus ensuring Sha ...
. 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
Key or The Key may refer to:
Common meanings
* Key (cryptography), a piece of information that controls the operation of a cryptography algorithm
* Key (lock), device used to control access to places or facilities restricted by a lock
* Key (map ...
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 32 rounds.
Due to the simplicity of its
key schedule
In cryptography, the so-called product ciphers are a certain kind of cipher, where the (de-)ciphering of data is typically done as an iteration of ''rounds''. The setup for each round is generally the same, except for round-specific fixed valu ...
, using the same eight key bytes in each round, Treyfer was one of the first ciphers shown to be susceptible to a
slide attack
The slide attack is a form of cryptanalysis designed to deal with the prevailing idea that even weak ciphers can become very strong by increasing the number of rounds, which can ward off a differential attack. The slide attack works in such a way ...
. This cryptanalysis, which is independent of the number of rounds and the choice of S-box, requires 2
32 known plaintexts and 2
44 computation time.
Implementation
A simple implementation of Treyfer can be done as follows
See also
*
Tiny Encryption Algorithm
In cryptography, the Tiny Encryption Algorithm (TEA) is a block cipher notable for its simplicity of description and implementation, typically a few lines of code. It was designed by David Wheeler and Roger Needham of the Cambridge Computer Lab ...
References
*
Broken block ciphers
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