Saam/ec2

[samantehrani]

• opens up support for EC_SECP256k1 wallets. removes KeyLength/AddressLength restrictions.
• Defines notion of Identifier to be used as Transaction.owner and Block.reward_key.
• Defines Address/Target to be Sha256(Identifier).
• removes signature_type from code base.

Identifiers are always of Odd length, except for the existing RSA_65537. Definition of Identifier is as follow and is backward compatible:
Let:

• k be a wallet key used for signing/verification.

• t be the key type of k when t∈T and T={RSA_65537, EC_SECP256K1, ...}

• Prefix be a unique one byte prefix a given type t. {EC_SECP256K1 = 0x01}

• PubRaw(k): be the raw public key bytes of given k.

• PubPadded(k): when PubRaw(k) % 2 = 0 -> PubPadded(k) = PubRaw(K).

• PubPadded(k): when PubRaw(k) % 2 = 1 -> PubPadded(k) = PubRaw(K) || 0x00 .

• If t = RSA_65537 -> Identifier(k) = PubRaw(k).

• If t != RSA_65537 -> Identifier(k)= p ​∥ PubPadded(K).