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RE: MUST implement AES-CBC for IPsec ESP

2007-01-21 09:07:44
Jorge Contreras wrote:
Please note that any responses to your question "Are any of these
encryption algorithms patented?" are being provided by individuals in the
spirit of helpfulness and open sharing of information.  Neither IETF nor
the IETF Trust provide assurances or advice as to whether or not
technology covered by IETF standards are covered by patent claims.  The
exclusive mechanism for soliciting and disclosing patent claims within the
context of IETF activity is specified in RFC 3979, as we have discussed
before.  Please do not take anyone's efforts to respond to your questions
as "official" IETF positions, as they are not and may not be relied upon
as such.

I didn't take anyone's comments on this list as any reassurance of anything
other than their own understanding of the situation. I just asked about
patent coverage because I wondered if anyone knew. This kind of question
comes up at other organizations I work with too. Asking a patent question on
an IETF list should not conflict with the "exclusive mechanism" you
describe.

You should realize that I, perhaps more so than others on this list, would
never rely on helpful and open emails on a public IETF list--no matter how
expert the writers are--for official reassurances about patents,
particularly third party patents. The people here don't read patent claims,
nor should they have to for this purpose. That is in part why I am in favor
of mandatory licensing by contributors in addition to disclosures.

/Larry


-----Original Message-----
From: Contreras, Jorge 
[mailto:Jorge(_dot_)Contreras(_at_)wilmerhale(_dot_)com]
Sent: Sunday, January 21, 2007 5:23 AM
To: Steven M. Bellovin; lrosen(_at_)rosenlaw(_dot_)com
Cc: ipsec(_at_)ietf(_dot_)org; ietf(_at_)ietf(_dot_)org; 
saag(_at_)mit(_dot_)edu
Subject: RE: MUST implement AES-CBC for IPsec ESP

Larry,

Please note that any responses to your question "Are any of these
encryption algorithms patented?" are being provided by individuals in the
spirit of helpfulness and open sharing of information.  Neither IETF nor
the IETF Trust provide assurances or advice as to whether or not
technology covered by IETF standards are covered by patent claims.  The
exclusive mechanism for soliciting and disclosing patent claims within the
context of IETF activity is specified in RFC 3979, as we have discussed
before.  Please do not take anyone's efforts to respond to your questions
as "official" IETF positions, as they are not and may not be relied upon
as such.

Regards,
Jorge


-----Original Message-----
From: Steven M. Bellovin [mailto:smb(_at_)cs(_dot_)columbia(_dot_)edu]
Sent: Saturday, January 20, 2007 6:28 PM
To: lrosen(_at_)rosenlaw(_dot_)com
Cc: ipsec(_at_)ietf(_dot_)org; ietf(_at_)ietf(_dot_)org; 
saag(_at_)mit(_dot_)edu
Subject: Re: MUST implement AES-CBC for IPsec ESP


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?


Almost certainly not.  DES was patented, but the patent was never
enforced; it has long since expired.  (Trivia: IBM filed a statement
saying that DES was royalty-free *if* used in one of the
NIST-approvedd
modes of operation.  But they never went after anyone who used it in
other ways.)  To my knowledge, 3DES was never patented; even if it had
been, it was first publicly described in 1979, so I doubt that any
patent would still be valid.

AES itself had to be unencumbered; see
http://csrc.nist.gov/CryptoToolkit/aes/pre-round1/aes_9709.htm#sec2d .
The designers of Rijndael never even attempted to patent it; see the
text quoted in RFC 3602 or the old Rijndael home page.

CBC dates from at least 1980 -- I seem to recall 1978, but I
don't have
a citation handy.

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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