@Misc{RRSY01,
author = { Ronald L. Rivest and Matthew John Barton Robshaw and Raymond Mark Sidney and Yiqun Lisa Yin },
title = { Enchanced block ciphers with data-dependent rotations },
howpublished = { U.S. Patent 6,269,163. Issued July 31, 2001. },
date = { 2001-07-31 },
OPTyear = { 2001 },
OPTmonth = { July 31, },
urla = { google-patent-page },
abstract = { A plaintext message to be encrypted is segmented
into a number of words, e.g., four words stored in
registers A, B, C and D, and an integer
multiplication function is applied to a subset of
the words, e.g., to the two words in registers B and
D. The integer multiplication function may be a
quadratic function of the form .function.(x)=x(ax+b)
or other suitable function such as a higher-order
polynomial. The results of the integer
multiplication function are rotated by lg w bits,
where lg denotes log base 2 and w is the number of
bits in a given word, to generate a pair of
intermediate results t and u. An exclusive-or of
another word, e.g., the word in register A, and one
of the intermediate results, e.g., t, is rotated by
an amount determined by the other intermediate
result u. Similarly, an exclusive-or of the
remaining word in register D and the intermediate
result u is rotated by an amount determined by the
other intermediate result t. An element of a secret
key array is applied to each of these rotation results,
and the register contents are then transposed. This
process is repeated for a designated number of rounds
to generate a ciphertext message. Pre-whitening and
post-whitening operations may be included to ensure
that the input or output does not reveal any
internal information about any encryption round.
Corresponding decryption operations may be used
to decrypt the ciphertext message.
},
}