Re: [RFC][DISCUSSION] Add RFC 4648 compliant data encoding API

Hi Am 2025-07-01 16:18, schrieb Larry Garfield:

I don't follow. Every function listed allows a timing mode to be set, so I presume that means every function *can* use constant-time. The implementation is, well, this RFC. :-) So I don't see why we can't just force constant-time everywhere and be secure-by-default.

Please see the note in the “Implementation” section. I wanted Ignace and the discussion to figure out the desired API from a “high level” perspective first, before checking individually whether or not a constant-time implementation is possible for each of the possible combinations of options, since depending on the API that is agreed-on certain combinations might not make it (allowing me to skip the effort of finding out how to do it constant time).

If there's a reason we cannot just blanket decide to use constant-time everywhere always, we need concrete examples of why that's a bad idea; and even then, I'd expect to be able to default to it.

A constant-time implementation generally is (measurably) slower than non-constant time implementation, but also see above.

For the long-names issue that Tim pointed out, perhaps drop "Variant" from the enum names? As they're namespaced, Base32::Ascii seems fairly self-explanatory.

You probably meant s/Tim/Rowan/. Best regards Tim Düsterhus