25519: remove unused const, safeguard against unreduced scalars (#8624)

* 25519: remove unused const, safeguard against unreduced scalars

No behavior change, but it makes the existing code better match
the forthcoming code for other curves.

Rename nonAdjacentForm() to slide(), remove an unneeded and
confusing constant, and do a reduction in slide() if 257 bits would
be required.

Note that in all the high-level functions, the top bit is always
cleared, so the reduction is never necessary. But since the low-level
functions are public, the check is a safe thing to have.

* 25519: make identityElement public, deprecate neutralElement

Also fix a few comments by the way.

0 files changed, 0 insertions, 0 deletions