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Re: [CFRG] HPKE and AEAD Authentication Tag Length

Joseph Salowey <joe@salowey.net> Tue, 24 August 2021 05:24 UTC

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From: Joseph Salowey <joe@salowey.net>
Date: Mon, 23 Aug 2021 22:24:37 -0700
Message-ID: <CAOgPGoBdSSiH=erYE0OV2hVCupUaGH3NU15DyiY4FfnQTuPg-A@mail.gmail.com>
To: Martin Thomson <mt@lowentropy.net>
Cc: IRTF CFRG <cfrg@irtf.org>
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Subject: Re: [CFRG] HPKE and AEAD Authentication Tag Length
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On Mon, Aug 23, 2021 at 6:24 PM Martin Thomson <mt@lowentropy.net> wrote:

> Curiously, the length of the tag is not in contention for any of these
> AEADs.  It's only if we take on something like CCM or OCB that it becomes
> relevant.
>
>
[Joe] There are short length tags defined for AES-GCM [RFC 5282] and some
implementations allow/force you to choose the tag length.   The HPKE draft
points to the NIST document for AES-GCM which also parameterizes the tag
length.   The draft also defines its own registry instead of reusing the
one defined by RFC 5116 which is very specific about tag length.




> On Tue, Aug 24, 2021, at 04:52, Joseph Salowey wrote:
> > In working on a Java HPKE implementation I found that specification
> > does not specify anything about the authentication tag length for the
> > AEAD cipher.  I opened issue #283
> > <https://github.com/cfrg/draft-irtf-cfrg-hpke/issues/238> and proposed
> > PR 239 <https://github.com/cfrg/draft-irtf-cfrg-hpke/pull/239> to
> > address this.
> >
> > Cheers,
> >
> > Joe
> > _______________________________________________
> > CFRG mailing list
> > CFRG@irtf.org
> > https://www.irtf.org/mailman/listinfo/cfrg
> >
>
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