[curves] Distribution-ready optimized code

[Trevor Perrin]

On Thu, Mar 19, 2015 at 11:36 AM, Samuel Neves <sneves at dei.uc.pt> wrote:
> On 03/19/2015 05:03 PM, Watson Ladd wrote:
>> What about mixed 1 and 4? Distribute asm a tool made.
>
> This has the same problem as 1: you don't simply distribute one assembly dump, you have to distribute one for each
> toolchain/ABI/etc combo.
[...]
>
> It's not really a major problem, but it is annoying enough that I would very much prefer if the tool came with the
> distribution. For that to happen, the tool must be portable, polished, etc. OpenSSL went with Perl, but I would prefer
> something better.


So the OpenSSL approach is to emit asm from scripts.  This allows
syntactic sugar (e.g. variable names for stack locations, loop
unrolling).  There's also support for translating to different
toolchain / ABI formats (e.g. it can convert AT&T syntax to Intel).

It seems like you're okay with this approach but want a higher-quality
tool that could be reused outside OpenSSL? (so asm source could be
written in "perlasm" or similar and be ingested by different
projects)?

This makes sense but I wonder if having the source file be a
string-processing script loses the ability to have code auditors or
formal-methods tools validate the code at a higher level?

I don't know that anyone's doing much formal validation of ECC
codebases yet, but it seems like a potential good idea.  If the input
source is a Perl script any formal validation tools would need to
understand Perl (not likely) or would need to understand asm, and be
re-run on every output flavor...


Trevor