Information About

Cast-128





Block Information

  Name CAST-128
  Caption Three rounds of the CAST-128 block cipher
  Designers Carlisle Adams and Stafford Tavares
  Publish Date 1996
  Derived To CAST-256
  Key Size 40 to 128 bits
  Block Size 64 bits
  Structure Feistel Network
  Rounds 12 or 16


In Cryptography , CAST-128 (alternatively '''CAST5''') is a Block Cipher used in a number of products, notably as the default Cipher in some versions of GPG and PGP . It has also been approved for Canadian government use by the Communications Security Establishment . The algorithm was created in 1996 by Carlisle Adams and Stafford Tavares using the '''CAST''' design procedure; another member of the CAST family of ciphers, CAST-256 (a former AES candidate) was derived from CAST-128. According to some sources, the "CAST" name is based on the Initials of its inventors, though Bruce Schneier reports the authors' claim that "the name should conjure up images of randomness" (Schneier, 1996).

CAST-128 is a 12- or 16-round Feistel Network with a 64-bit Block Size and a Key Size of between 40 to 128 Bit s (but only in 8-bit increments). The full 16 rounds are used when the Key Size is longer than 80 bits.
Components include large 8×32-bit S-box es based on Bent Function s, key-dependent rotations, Modular addition and subtraction, and XOR operations. There are three alternating types of round function, but they are similar in structure and differ only in the choice of the exact operation (addition, subtraction or XOR) at various points.

Although Entrust holds a Patent on the CAST design procedure, CAST-128 is available worldwide on a royalty-free basis for commercial and non-commercial uses.


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