Hyrum’s Law in Golang

Hah, I wrote the crypto/rsa comments. We take Hyrum's Law (and backwards compatibility [1]) extremely seriously in Go. Here are a couple more examples:

- We randomly read an extra byte from random streams in various GenerateKey functions (which are not marked like the ones in OP) with MaybeReadByte [2] to avoid having our algorithm locked in

- Just yesterday someone reported that a private ECDSA key with a nil public key used to work, and now it doesn't, so we probably have to make it work again [3]

- Iterating over a map uses a randomized order to avoid exposing the internals

- The output of rand.Rand is considered part of the compatibility promise, so we had to go to great lengths to improve it [4]

- We discuss all the time what commitments to make in docs and what behaviors to disclaim, knowing we can never change something documented and probably something that's not explicitly documented as "this may change" [6]

[1]: https://go.dev/doc/go1compat

[2]: https://pkg.go.dev/crypto/internal/randutil#MaybeReadByte

[3]: https://go.dev/issue/70468

[4]: https://go.dev/blog/randv2

[5]: https://go.dev/blog/chacha8rand

[6]: https://go-review.googlesource.com/c/go/+/598336/comment/5d6...

> We randomly read an extra byte from random streams in various GenerateKey functions (which are not marked like the ones in OP) with MaybeReadByte [2] to avoid having our algorithm locked in

You don't seem to do that in ed25519. Back before ed25519.NewKeyFromSeed() existed, that was the only way to derive a public Ed25519 key from a private key, and I'm pretty sure I've written code that relied on that (it's easy to remember, since I wasn't very happy about it, but this was all I could do). The documentation of ed25519.GenerateKey mentions that the output is deterministic, so kudos for that. It seems you've really done a great job with investigating and maintaining ossified behavior in the Go cryptography APIs and preventing new ones from happening.