Infer key type from signature and public key bytes

[robdefeo]

Is your feature request related to a problem? Please describe. Mailchain requires public keys to, encrypt messages and calculate the address. While ethereum and other protocols support a single key type, substrate supports, ed25519, sr25519, and secp256k1. To reliably determine a public key type the key type must be tested.

Describe the solution you'd like Create a method that can determine the key type from the public and private key bytes combination.

• [ ] create method in crypto/multikey
• [ ] method signature GetKeyKindFromSignature(publicKey, message, sig []byte, keyTypes []???) (crypto.PublicKey, error)
• [ ] keyTypes []string or keyTypes []crypto.PublicKey?
• [ ] check each key type to see if signature, message, and public key combination is valid
  • [ ] create PublicKey from []byte
  • [ ] check output of .Verify()
• [ ] check all candidate key types
• [ ] if a single match return crypto.PublicKey
• [ ] no match return error
• [ ] multiple match return inconsistent/inconclusive error

Additional context

• Not all protocols have this requirement.
• More key types will be added in the future

[robdefeo]

@Despire this might be an interesting one for you once #345 is completed?

[Despire]

Looks interesting ! :) you can assign me and once #345 is ready I'll start.

[Despire]

This issue can be closed. @robdefeo