[Cryptography] Exotic Operations in Primitive Construction
Dave Horsfall
dave at horsfall.org
Thu Oct 1 02:49:00 EDT 2020
On Wed, 30 Sep 2020, Peter Gutmann wrote:
> If you're referring to an implementation in C, it's not even that any
> more, any compiler from the last 15-20 years has a rotate recogniser and
> will translate 'x << y | x >> ( wordsize - y )' into a single rotate
> instruction.
Thank you :-) I was trying to figure out how to do a rotation in C, but
I'm a little rusty now; all I could think of was a single shift and test
the sign bit etc.
Rotation of course is about as important in crypto as is XOR, or, for that
matter, the famous NSA instruction ("population count") on the Cray
series.
-- Dave
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