PKEY CMAC timings

[Hal Murray]

In the context of making things go fast/clean, do I need a reset?  If so, why?

My straw man is that setup has 3 stages:
  1: get storage and whatever for the cipher
  2: setup tables and such for a key
  3: init internal data

In the same key case, the basic operation is
  Init (does step 3)
  Update
  Final

I think setup steps 1 and 2 can be done with something like
  Setup(ctx, cipher, key+length)

A NULL cipher means keep using the current one - no allocs.

With something like that, I'd be happy to have a ctx per cipher.

Setup and Init can be merged into one function if a NULL key means keep using 
the old one.  I think it's slightly cleaner (and faster) to leave them split.



-- 
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