Re: [PATCH 2/2] salsa20_i586: Salsa20 stream cipher algorithm (i586 version)

["Tan Swee Heng" <thesweeheng@gmail.com>]

Hi Sebastian,

On Dec 6, 2007 5:49 AM, Sebastian Siewior <linux-crypto@ml.breakpoint.cc> wrote:
> The patch is a large one. Do you thing all those comments are requried
> or helping to understand what is going on?
Actually no, I don't think the comments outside of the functions are
that helpful. But let me explain why I left them in there:

The assembly code was written by Bernstein 2 years ago in 2005 (see
<http://cr.yp.to/snuffle/salsa20/x86-pm/salsa20.s>). Since then I
suppose folks have vetted the code. These folks may want reassurance
that I did not corrupt it when adding indentations. By leaving the
comments and extraneous functions intact, I was HOPING they can verify
it with "diff -b".

> Besides that, I saw the keysetup routine is also included in assembly.
> Is the computed key any different from the C version? *I* would prefer
> to share the keysetup code with the C version because it is not a
> performace critical part.
The keysetup() should be the same as the C version... except that I've
previously modified the C version to use key length in bytes while the
assembly version uses bits! :-) I could change the C code back. But I
personally prefer to use the assembly version since it was distributed
as a "self-contained and complete solution" in Bernstein's
"salsa20.s".

> There are a few labels like '_label:' and 'label:' One of them should be
> enough or am I missing something?
You are absolutely right. I forgot to remove them when removing
".globl _ECRYPT_* ".

Hope is a fickle thing. I just tried "diff -b" and it did not work as
I hoped. My removal of ".globl _ECRYPT_* " confuses diff. That being
the case, I will go with everyone's wish to remove the extraneous
comments. As for folks who want to verify that I did not corrupt the
assembly code, I will also provide the script I used to automate the
process. (I will do all these in a separate post.)

Swee Heng