[RFC PATCH] arm64: add support for AES in CCM mode using Crypto Extensions

On 25 February 2014 08:16, Herbert Xu [off-list ref] wrote:

On Tue, Feb 25, 2014 at 08:12:36AM +0100, Ard Biesheuvel wrote:

quoted

Do you have any comments specifically about using an inner blkcipher
instance to implement the aead?

Indeed, the inner block cipher looks superfluous since it's only
used once by ccm and there is no nesting similar to aesni-intel.

Inner algorithms are only needed if you want to nest it, e.g.,
through fpu().  Otherwise I don't see any difference vs. calling
the underlying functions directly, especially since you seem to
be calling them directly anyway.

Well, the problem is that aead does not provide the blkcipher walk
API, which means it is up to the caller to map/unmap the scatterlists
and keep track of the in and out pointers etc.

For the authenticate-only data, this is manageable as you are only
dealing with input, but when dealing with both in- and output, as in
the core of CCM, it becomes very tedious.
So instead, I have opted for an inner blkcipher instance which takes
care of all of that. Could you suggest another approach that if
preferable?

Thanks,
Ard.