[openssl-dev] AAD length with AES cipher

[Benjamin Kaduk]

On 10/23/2015 01:38 PM, Vijay Singh wrote:
>
> It seems that the library uses 13 bytes of AAD data. Is this per-spec?
> The reason I am asking is that the new Intel AESNI APIs that provide
> HW support seem to require AAD as a multiple of 4 bytes, and 0 padding
> the AAD changes the computed auth value.
>

Sorry, is the claim that the authentication tag is 13 bytes, or that
some portion of the codebase is supplying additional authenticated data
of length 13 bytes, or something else?  OpenSSL does make use of the
AESNI APIs for GCM, so it is not clear where you are observing this
seemingly incompatible behavior.

> Any insights are much appreciated.
>
>

That will be difficult without better pointers to what behavior your are
observing.

-Ben Kaduk
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