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

[Ard Biesheuvel]

On 25 February 2014 08:16, Herbert Xu <herbert at gondor.apana.org.au> wrote:
> On Tue, Feb 25, 2014 at 08:12:36AM +0100, Ard Biesheuvel wrote:
>>
>> 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.