Make signing methods clearer

[Firaenix]

There are different ways to sign a message or message digest dependent on:

• Endianness of the digest when generating ephemeral K
• SHA2 hashing algorithm chosen for signing (SHA256, SHA256d, etc)

Maybe a good way to approach this is having simple sign methods on different structs (like Transaction)

• Transaction Signing

  • Used for signing Sighash buffers
  • Reversed K: true
  • Double SHA256

• Traditional ECDSA Signatures

  • Used for signing any message to be compatible with ECDSA libraries outside of Bitcoin (SSH, Code signing, etc)
  • Reversed K: false
  • Single SHA256

• Bitcoin Signed Messages (BSM)

  • Used for verifying a message has been signed with a Bitcoin P2PKH Address
  • Requires being able to recover a public key from a signature.
  • Reversed K: optional (?)
  • Double SHA256

[Firaenix]

Idea:

1. Transaction.sign() - Sighash signing
2. PrivateKey.signBitcoinMessage() - BSM Signing
3. PrivateKey.sign() / PrivateKey.signTraditional() - Non Bitcoin/Standard ECDSA message signing

[Firaenix]

Or if you're signing something to be verified with an Address (BSM), Address.signMessage()

[utxo-detective]

[utxo-detective]

Or if you're signing something to be verified with an Address (BSM), Address.signMessage()

@Firaenix how would this work? You'd need to still have a private key? Wouldnt it be the same as PrivateKey.signBitcoinMessage()? When you need to verify it you can just get the address from the private key

[Firaenix]

Released in 1.1.0