Steven,
Counter mode is described in:
W. Diffie and M. E. Hellman, "Privacy and Authentication: An
Introduction to Cryptography," Proceedings of the IEEE,
Vol. 67, March 1979, pp. 397-427.
See Figure 18 on page 417.
http://www-ee.stanford.edu/%7Ehellman/publications/32.pdf
-- Bart Preneel
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On Sat, 20 Jan 2007, Steven M. Bellovin wrote:
On Sat, 20 Jan 2007 14:45:26 -0800
"Lawrence Rosen" <lrosen(_at_)rosenlaw(_dot_)com> wrote:
For ESP encryption algorithms, the document that was sent out for
Last Call contains the following table:
Requirement Encryption Algorithm (notes)
----------- --------------------
MUST NULL (1)
MUST- TripleDES-CBC [RFC2451]
SHOULD+ AES-CBC with 128-bit keys [RFC3602]
SHOULD AES-CTR [RFC3686]
SHOULD NOT DES-CBC [RFC2405] (3)
The Last Call comment suggests changing the "SHOULD+" for AES-CBC
to "MUST."
Are any of these encryption algorithms patented?
[...]
That leaves CTR mode. I doubt very much that it's patented, since it's
been very well known for many years and NIST rarely standardizes
patented algorithms in this space (which I know you appreciate...).
However, I don't have any citations to prove this negative.
--Steve Bellovin, http://www.cs.columbia.edu/~smb
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