Crypt::Serpent is a Perl implementation of the Serpent block cipher.
Serpent is a 128-bit block cipher, meaning that data is encrypted and
decrypted in 128-bit chunks. The key length can vary, but for the
purposes of the AES it is defined to be either 128, 192, or 256 bits.
This block size and variable key length is standard among all AES
candidates and was one of the major design requirements specified by
NIST. The Serpent algorithm uses 32 rounds, or iterations of the main
algorithm.
from Stephan A. Rickauer (MAINTAINER)