- arti#448 and arti!607 highlight an issue with upgrading `rsa`: namely,
the `x25519-dalek` version previously used has a hard dependency on
`zeroize` 1.3, which creates a dependency conflict.
- However, `x25519-dalek` version `2.0.0-pre.1` relaxes this dependency.
Reviewing the changelogs, it doesn't look like that version is
substantially different from the current one at all, so it should be
safe to use despite the "prerelease" tag.
- The new `x25519-dalek` version also bumps `rand_core`, which means we
don't have to use the RNG compat wrapper in `tor-llcrypto` as much.
closes arti#448
This only affects uses of thread_rng(), and affects them all more or
less indiscriminately. One test does not work with
ARTI_TEST_PRNG=deterministic; the next commit will fix it.
For this one I just wrote some "are things completely broken" tests
for the rand_compat wrappers. These won't detect subtle biases in
the RNGs! They'll only let you know if the wrappers have screwed up
in some way that always sets a given bit to 1 or 0.