Re: [CRYPTO] is it really optimized ?

[Francis Moreau]

On 4/17/07, Roland Dreier <rdreier@xxxxxxxxx> wrote:
>  > > I wonder if there's some way you can cache the last caller and reload
>  > > the key lazily (only when it changes).
>  >
>  > yes something that allows crypto drivers to detect if the key has
>  > changed would be good.
>
> It seems trivial to keep the last key you were given and do a quick
> memcmp in your setkey method to see if it's different from the last
> key you pushed to hardware, and set a flag if it is.  Then only do
> your set_key() if you have a new key to pass to hardware.
>
> I'm assuming the expense is in the aes_write() calls, and you could
> avoid them if you know you're not writing something new.

that's a wrong assumption. aes_write()/aes_read() are both used to
access to the controller and are slow (no cache involved).

thanks
--
Francis
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