Why is that 2^48 input blocks rather than 2^34.5 input blocks?
Because he wants to lower the security level. The original text
recommends switching at 2^{34.5} input blocks, corresponding to a
success probability of 2^{-60}, whereas his text recommends switching at
2^{48} blocks, corresponding to a success probability of 2^{-32}.
Atul
On 2017-02-14 11:45, Yoav Nir wrote:
Hi, Quynh
On 14 Feb 2017, at 20:45, Dang, Quynh (Fed) <quynh.d...@nist.gov>
wrote:
Hi Sean and all,
Beside my suggestion at
https://www.ietf.org/mail-archive/web/tls/current/msg22381.html [1],
I have a second suggestion below.
Just replacing this sentence: "
For AES-GCM, up to 2^24.5 full-size records (about 24 million) may
be
encrypted on a given connection while keeping a safety margin of
approximately 2^-57 for Authenticated Encryption (AE) security.
" in Section 5.5 by this sentence: " For AES-GCM, up to 2^48
(partial or full) input blocks may be encrypted with one key. For
other suggestions and analysis, see the referred paper above."
Regards,
Quynh.
I like the suggestion, but I’m probably missing something pretty
basic about it.
2^24.5 full-size records is 2^24.5 records of 2^14 bytes each, or
(since an AES block is 16 bytes or 2^4 bytes) 2^24.5 records of 2^10
blocks.
Why is that 2^48 input blocks rather than 2^34.5 input blocks?
Thanks
Yoav
Links:
------
[1] https://www.ietf.org/mail-archive/web/tls/current/msg22381.html
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