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Re: [kitten] Question about AES mode in Kerberos

Nico Williams <nico@cryptonector.com> Fri, 13 January 2023 21:38 UTC

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Date: Fri, 13 Jan 2023 15:37:46 -0600
From: Nico Williams <nico@cryptonector.com>
To: Greg Hudson <ghudson@mit.edu>
Cc: Olga Kornievskaia <aglo@umich.edu>, Luke Howard Bentata <lukeh=40padl.com@dmarc.ietf.org>, "kitten@ietf.org" <kitten@ietf.org>
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Subject: Re: [kitten] Question about AES mode in Kerberos
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On Fri, Jan 13, 2023 at 12:42:12PM -0600, Nico Williams wrote:
> Because GCM is limited to 2^32 blocks of ciphertext with one key we'd
> have to derive new sub-session keys before rolling over the block
> counter.

Luke points out that because we'd put the GSS sequence number into the
IV we don't have to worry about this.  (And we can't have per-message
tokens that are 2^36 bytes in size either.)

Nico
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