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 ...

, CS-Cipher (for ''Chiffrement Symétrique'') 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 ...

invented by

Jacques Stern Jacques Stern (born 21 August 1949) is a cryptographer, currently a professor at the École Normale Supérieure. He received the 2006 CNRS Gold medal. His notable work includes the cryptanalysis of numerous encryption and signature schemes, th ...

and

Serge Vaudenay Serge Vaudenay (born 5 April 1968) is a French cryptographer and professor, director of the Communications Systems Section at the École Polytechnique Fédérale de Lausanne Serge Vaudenay entered the École Normale Supérieure in Paris as a '' ...

in 1998. It was submitted to the NESSIE project, but was not selected. The algorithm uses a key length between 0 and 128 bits (length must be a multiple of 8 bits). By default, the cipher uses 128 bits. It operates on blocks of 64 bits using an 8-round

Feistel network In cryptography, a Feistel cipher (also known as Luby–Rackoff block cipher) is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel, who did pioneering research whi ...

and is optimized for 8-bit

processor Processor may refer to: Computing Hardware * Processor (computing) **Central processing unit (CPU), the hardware within a computer that executes a program *** Microprocessor, a central processing unit contained on a single integrated circuit (I ...

s. The round function is based on the

fast Fourier transform A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in th ...

and uses the binary expansion of e as a source of "

nothing up my sleeve number In cryptography, nothing-up-my-sleeve numbers are any numbers which, by their construction, are above suspicion of hidden properties. They are used in creating cryptographic functions such as hashes and ciphers. These algorithms often need rando ...

s".

References

* Feistel ciphers {{crypto-stub