Transaction proposal protocol

gistfile1.txt

transaction_proposal: {
  raw,
  xpubs[],
  m,
  input_metadata: [
    {
      input_transaction, // (optional for participants with no access to the blockchain)
      path || paths[],
      sighash_type (defaults to SIGHASH_ALL)
    } || null
  ],
  output_metadata: [
    {
      path || paths[]
    } || null
  ]
}

sighash_type: part of tx_proposal, or part of input_metadata?

should we include extended master public keys and the threshold (m in m-of-n) in each transaction proposal?

check if we need to include redeemScript in metadata.

Advantage of including master public keys in each tx proposal is that the participants don't have to store them as state. This also reduces privacy leaks if a participant is compromised.

The disadvantage of including them is that the tx proposal now becomes more sensitive and might need to protect it more than we would otherwise.

I believe we don't need to include redeemScripts in metadata - they can just be in the properly formatted scriptSigs. OP_0 SIG1 SIG2 REDEEM where SIG1 / SIG2 are replaced with OP_0 if not yet populated.

+1 on the redeem script not being necessary