[FFmpeg-devel] [PATCH 07/10] checkasm: add tests for AES

[Henrik Gramner]

On Tue, Oct 13, 2015 at 11:58 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> On Tue, Oct 13, 2015 at 5:55 PM, Henrik Gramner <henrik at gramner.com> wrote:
>> On Tue, Oct 13, 2015 at 11:28 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
>>> Not really that important, but unless this increases FATE time
>>> significantly, I would recommend a much larger MAX_COUNT, and multiple
>>> iterations (e.g #define an ITER_COUNT), so that the testing is more
>>> extensive over random inputs.
>>
>> Each count is in the order of microseconds, but with this kind of
>> algorithm I don't see how just iterating over a larger buffer will
>> increase the chance of finding any issues.
>
> The random stream will be of longer length, providing more bytes of
> data over which aes runs (and thereby covering more bit patterns).
> This was my motivation.

That certainly makes sense in some cases but it doesn't really apply
here IMO since there's no specific bit pattern in the input buffer
that could trigger a different behavior such as overflows etc. (unless
you're trying to find flaws in the AES-NI instructions themselves, but
that seems pretty far fetched).