Re: [Cfrg] request for comments on "Generation of Deterministic Initialization Vectors (IVs) and Nonces"

"Jim Schaad" <ietf@augustcellars.com> Wed, 20 July 2011 16:58 UTC

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From: "Jim Schaad" <ietf@augustcellars.com>
To: "'Peter Gutmann'" <pgut001@cs.auckland.ac.nz>, <dharkins@lounge.org>
References: <49fd928bf94d1d1920df676bb61fa198.squirrel@www.trepanning.net> <E1QjRXj-0002HE-HM@login01.fos.auckland.ac.nz>
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Date: Wed, 20 Jul 2011 09:57:52 -0700
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Cc: mcgrew@cisco.com, cfrg@irtf.org
Subject: Re: [Cfrg] request for comments on "Generation of Deterministic Initialization Vectors (IVs) and Nonces"
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That is completely correct.  SIV requires two passes for the sender - but
only one pass for the recipient.

> -----Original Message-----
> From: cfrg-bounces@irtf.org [mailto:cfrg-bounces@irtf.org] On Behalf Of
> Peter Gutmann
> Sent: Wednesday, July 20, 2011 12:50 AM
> To: dharkins@lounge.org; pgut001@cs.auckland.ac.nz
> Cc: mcgrew@cisco.com; cfrg@irtf.org
> Subject: Re: [Cfrg] request for comments on "Generation of Deterministic
> Initialization Vectors (IVs) and Nonces"
> 
> "Dan Harkins" <dharkins@lounge.org> writes:
> 
> >Let me remind everyone of SIV mode*. It's a CTR mode derivative but is
> >resistant to nonce misuse. Unlike CBC, the nonce doesn't need to be
> >unguessable. And it even provides a strong assurance of security if the
> >nonce is reused.
> 
> Doesn't SIV require the entire message to be buffered, which makes it
> unusable in streaming implementations?
> 
> [Checks]
> 
> Unless I've misinterpreted some part of Fig.3 and Fig.8 of RFC 5297, this
can't
> be used in a streaming implementation because the CMAC operation to
> create the IV has to make a complete pass over the message before you can
> start encrypting (this is also similar to a key-wrap mechanism that Colin
Plumb
> and I came up with for RFC 3211, although it'd need a tweak to use a
proper
> MAC for full integrity-protection, it was designed for non-expanding 512-
> byte disk sector encryption and dates from the early 1990s, so it predates
> pretty much all of the work that newer modes and mechanisms are built on).
> SIV is quite nice for something like 802.11, SRTP, DTLS, and others, but
> unfortunately won't work as a general-purpose mechanism.
> 
> Are there any IP issues around SIV?
> 
> Peter.
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