{sign|verify}message replacement

The conversation discusses the handling of scripts with OP_CLTV and OP_CSV by verifiers. The concern is whether they always succeed or if an nLockTime and nSequence should be included in the proof that can be parsed out and displayed to verifiers. It is assumed that any signatures in the scriptSig/witness data would have no sighash type. In response to a comment about the potential for soft forks to make old nodes accept invalid message signatures as valid, it is suggested that the scriptPubKey is derived directly from the address in all cases, so any unknown witness version would have to be committed to in the address itself. While it may be possible to fool someone into thinking they own an address, ultimately if funds can be spent from it today, it proves that the spender can spend today, which is the purpose of the tool. When discussing a new signature format, it is suggested that it should support not only proof of receipt at a given address, but also proof of funds. It is also suggested that it should avoid disclosing public keys for existing or future UTXOs, although this may require something MAST-like first. Finally, it is suggested that old nodes should check for standardness of spending scripts and report non-standard scripts as either invalid outright or highly questionable, with a warning being useful in case the verifier is running old software.