|developer||Carlisle Adams , Stafford Tavares|
|Key length||40 to 128 bits|
|Block size||64 bit|
|Round||12 for keys up to 80 bits, above 16|
|Best known cryptanalysis|
|As of 2014, no efficient cryptanalysis is publicly known|
CAST is a symmetrical block cipher with a 64- bit block length and a key length of 40 to 128 bits. Alternative names are CAST-128 or CAST5 . The CAST algorithm was named after its developers C arlisle A dams and S tafford T avares and a patent was applied for in 1996 . CAST may be used worldwide license-free in both commercial and non-commercial applications. Because of its higher speed compared to DES , CAST is also suitable for real-time applications.
The successor CAST-256 was a candidate in the AES challenge.
To date, CAST has not yet been broken, which is why it is included in many applications such as PGP .
CAST is a Feistel cipher . In each round, a data word is linked with a key word (depending on the round by addition, XOR or subtraction) and rotated depending on the key. Then it is divided into four sections of 8 bits each, which are each substituted in an 8x32 bit S-Box . Their outputs are linked to one another using the addition , subtraction and XOR operations . Their order is rotated from round to round. With the result, the other data word (the second half of the block) is finally modified by XOR.
- CM Adams: Constructing Symmetric Ciphers Using the CAST Design Procedure. In: Designs, Codes, and Cryptography. 12, No. 3, 1997, pp. 283-316. jya.com ( Memento from July 1, 2011 in the Internet Archive ), (English).
- Explanation and diagram of the procedure on regenechsen.de