Ed25519: generation, storage, sign & verify

[karimodm]

Description

As far as I observed in the code, stronghold currently support Ed25519 signing and verification in relation to BIP39 mnemonics.
Due to the use of Ed25519 across the board we also need facilities to securely generate Ed25519 key pairs, storing them at rest, sign messages and verify them.

Motivation

Ed25519 has emerged in our discussion to be the selected standard we are gonna use pretty much for every signing purpose.

Requirements

Write a list of what you want this feature to do.

1. Key generation using good source of entropy (time bounded though);
2. Non-volatile secure storage of private key;
3. Memory guarantees for private key;
4. Sign arbitrary messages;
5. Verify arbitrary messages -- this may be optional as it is not a "secure" operation, but since the rest it is needed it kinda makes sense to implement this as well.

Open questions (optional)

1. Similarly to signing, we should establish an encryption standard that we want to establish across the board; so far I am only aware of Keccak-f[1600] sponges used by the Stream guys,

Are you planning to do it yourself in a pull request?

No.