NIIBE Yutaka <[email protected]> writes:

> I checked other compilers today.

Thanks for investigating! Questions:

1. Do the changes on branch
   https://git.lysator.liu.se/nettle/nettle/-/tree/sc-is_zero?ref_type=heads
   help?

2. If you install valgrind (including header files), do the recently
   added tests for side-channel silence fail when nettle is built with a
   problem compiler? They're intended to catch this kind of issues (even
   if coverage isn't yet that great).

If it's too difficult or too brittle to get compilers to do the intended
thing, we'll have to add assembly implementation for all archs of
interest. I think there were similar issues, in particular with clang,
for gmp's mpn_sec_tabselect, and that's now in assembly for the many
archs.

It's unfortunate if assembly is needed for security, not just
performance, but that's already the case for AES, where the generic
implementation is leaky.

Regards,
/Niels

-- 
Niels Möller. PGP key CB4962D070D77D7FCB8BA36271D8F1FF368C6677.
Internet email is subject to wholesale government surveillance.
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