Fixup rand

[cbeck88]

I tried to uprev our version of ed25519-dalek but I ran into two issues:

1: missing #[cfg(feature = rand)] in secret.rs ( I think this is a further case of #108 ), we are building with these features:

..., default-features = false, features = ["alloc", "nightly", "serde", "u64_backend"] }

2: we lost Default trait on SecretKey, I don't know if that was intentional API change? but atm we are using that anyways, please lmk! thank you

[tarcieri]

I don't know if that was intentional API change?

IMO SecretKey should NOT have a Default

[cbeck88]

@tarcieri yah I guess I agree -- but if it's going to be removed, I think there should be semantic versioning around the change, otherwise cargo is going to do bad things

[cbeck88]

regarding the "Default" thing:
at this point we've been patching for like 4 months -- it will have little impact on mobilecoin how you decide to think about semver here. i'm happy to remove the Default thing if that will help the PR land

[isislovecruft]

I removed Default on SecretKey on purpose. It was there because clear_on_drop required it, but with it, I would worry about mistakes in accidentally initialising a SecretKey to all zeros. I'm happy to take the rest of this PR.

[isislovecruft]

Is there a reason why you wanted Default for SecretKey?

[cbeck88]

not really, we were just using it, we can stop using it

all i'm pointing out is, casually removing derive(Default) from public structs is a breaking change

[cbeck88]

rebased on master and removed the re-addition of Default

[cbeck88]

hmm, after rebase, I again can't build at this revision due to std/no_std issues :(

Will investigate further

[cbeck88]

closing in favor of #139 (comment)