RFC 2144 (rfc2144) - Page 2 of 15
The CAST-128 Encryption Algorithm
Alternative Format: Original Text Document
RFC 2144 CAST-128 Encryption Algorithms May 1997
candidate for general-purpose use throughout the Internet community
wherever a cryptographically-strong, freely-available encryption
algorithm is required.
Adams [Adams] discusses the CAST design procedure in some detail;
analyses can also be obtained on-line (see, for example, [Web1] or
[Web2]).
2. Description of Algorithm
CAST-128 belongs to the class of encryption algorithms known as
Feistel ciphers; overall operation is thus similar to the Data
Encryption Standard (DES). The full encryption algorithm is given in
the following four steps.
INPUT: plaintext m1...m64; key K = k1...k128.
OUTPUT: ciphertext c1...c64.
1. (key schedule) Compute 16 pairs of subkeys {Kmi, Kri} from K
(see Sections 2.1 and 2.4).
2. (L0,R0)