helpers: provide helpers to generate keys

[odeke-em]

Am currently writing code to test out the bug fix for tendermint/tendermint#514 in which we have a dishonest peer requesting a non-existent block height from a reactor and that requires a whole lot of setup.

I currently see that we have helpers for PrivKeyEd25519

go-crypto/priv_key.go

Lines 99 to 114 in 1bc8de4

	func GenPrivKeyEd25519() PrivKeyEd25519 {
	privKeyBytes := new([64]byte)
	copy(privKeyBytes[:32], CRandBytes(32))
	ed25519.MakePublicKey(privKeyBytes)
	return PrivKeyEd25519(*privKeyBytes)
	}
	// NOTE: secret should be the output of a KDF like bcrypt,
	// if it's derived from user input.
	func GenPrivKeyEd25519FromSecret(secret []byte) PrivKeyEd25519 {
	privKey32 := Sha256(secret) // Not Ripemd160 because we want 32 bytes.
	privKeyBytes := new([64]byte)
	copy(privKeyBytes[:32], privKey32)
	ed25519.MakePublicKey(privKeyBytes)
	return PrivKeyEd25519(*privKeyBytes)
	}

However, trying to generate the public key using our package is quite a bit of work, IMHO we should make it simple to generate a public Ed25519 key that conforms to our package and not just to the Go crypto library. I suspect some other developers might need this in the future.

[odeke-em]

/cc @ethanfrey @ebuchman @cloudhead

[ethanfrey]

What about GenPrivKeyEd25519().PubKey()?

That's what I do, and your logic would do under the hood. Not too much work, no?

[odeke-em]

Thanks @ethanfrey, and my apologies for the late reply, I was off from here since the weekend, but am back.

As per your recommendation and exhibit above, I've opened #35 in which we can provide a high level view of docs for go-crypto to easily transfer such knowledge to other developers and provide some more documentation. I'll close this issue in favor of the mentioned one.