BIP 372 guide to Draft PSBT pay-to-contract tweak fields, original keys, signer checks, supported scripts, compatibility and missing vectors.
This guide explains BIP 372 pay-to-contract PSBT in plain English. It covers the problem behind the BIP, why it matters and whether the proposal is part of Bitcoin today.
BIP 372 pay-to-contract PSBT: A contract message is hashed into a scalar and added times G to an original public key. Spending needs the original secret plus the same tweak modulo the curve order.
A node operator is checking BIP 372 pay-to-contract PSBT. PSBT_IN_P2C_TWEAK uses key type 0x19, a 33-byte compact original public key as keydata and a 32-byte tweak as valuedata.
BIP 372 remains Draft, requires BIP 174 and has a work-in-progress implementation with test vectors still marked TBD. Do not advertise interoperable support without bilateral version testing.
A contract message is hashed into a scalar and added times G to an original public key. Spending needs the original secret plus the same tweak modulo the curve order.
PSBT_IN_P2C_TWEAK uses key type 0x19, a 33-byte compact original public key as keydata and a 32-byte tweak as valuedata. BIP 340 keys are represented with a prefixed compressed form.
The signer should identify a controlled original key, apply the supplied tweak, verify that the result matches the key committed in the input script and only then produce ECDSA or Schnorr signature material.
The draft describes several bare, legacy and SegWit v0 scripts. Its compatibility discussion warns that post-v0 witness forms, including Taproot, may need extra treatment despite broader motivation text.
A malicious or mistaken tweak can redirect signing authority. Never apply an unverified scalar, accept zero or out-of-range encodings or sign without matching the resulting public key to the actual spent output.
Developers test the proposal with made-up data on an isolated test network. They check normal cases and deliberately invalid cases. Different implementations should reach the same result before anyone relies on the proposal.
BIP 372 pay-to-contract PSBT: A contract message is hashed into a scalar and added times G to an original public key.
BIP 372 remains Draft, requires BIP 174 and has a work-in-progress implementation with test vectors still marked TBD.
A contract message is hashed into a scalar and added times G to an original public key.
PSBT_IN_P2C_TWEAK uses key type 0x19, a 33-byte compact original public key as keydata and a 32-byte tweak as valuedata.
BIP 372 addresses a real external-signer gap for pay-to-contract outputs, but its Draft status and missing vectors demand conservative interoperability testing. A signer must verify the tweak against the spent script before using any secret key.
Check the current specification status and the documentation for the exact implementation you operate before moving production funds or changing a mining node.
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