Implements the send half of the onchain zaps plan: a minimal, fund-safe
BIP-174 PSBT pipeline plus the OnchainZapBuilder and `NostrSigner.signPsbt`.
Every cryptographic step is validated against the BIP-341 wallet test
vectors.
nipBCOnchainZaps/psbt/:
- BitcoinIO: little-endian Bitcoin consensus byte reader/writer (u16/u32/u64,
compact-size varint, var-bytes).
- BitcoinTransaction: OutPoint / TxIn / TxOut / transaction model with legacy
and BIP-144 segwit serialization, segwit-aware parsing, and witness-stripped
txid. Validated against the genesis coinbase tx and the BIP-341 9-input
unsigned tx.
- TaprootSigHash: BIP-341 SigMsg + TapSighash tagged hash for key-path spends.
All six base sighash types plus both ANYONECANPAY variants verified against
the seven BIP-341 keyPathSpending vectors.
- Psbt: BIP-174 container subset (global unsigned-tx, per-input witness-utxo /
tap-internal-key / tap-key-sig / sighash-type, per-output tap-internal-key).
Unknown records round-trip verbatim. Typed accessor extensions.
- PsbtSigner: signs the key-path P2TR inputs a given private key controls —
derives the BIP-341 tweaked key, computes the all-inputs sighash, produces a
BIP-340 Schnorr signature. Leaves inputs the key does not control untouched.
- PsbtFinalizer: moves tap-key-sigs into the witness stack, yields a
broadcastable transaction.
nipBCOnchainZaps/build/:
- OnchainZapBuilder: largest-first coin selection + unsigned-PSBT assembly for
a NIP-BC zap. Sender spends from / changes back to the single Taproot address
derived from their Nostr pubkey; recipient output pays the recipient's
derived address. Dust-aware change handling, InsufficientFundsException,
self-zap and dust-amount guards.
nipBCOnchainZaps/taproot/:
- TaprootAddress.tweakSecretKey: BIP-341 taproot_tweak_seckey (key-path-only),
including the odd-y internal-key negation. Validated against the BIP-341
vector's tweakedPrivkey.
Secp256k1Instance: new `privKeyNegate` primitive across commonMain expect +
jvm / android / native actuals.
Signer hierarchy — new `NostrSigner.signPsbt(psbtHex): String`:
- NostrSignerSync / NostrSignerInternal: real implementation.
- NostrSignerWithClientTag: delegates to the wrapped signer.
- NostrSignerRemote (NIP-46) and NostrSignerExternal (NIP-55): throw
SignerExceptions.UnsupportedMethodException — the bunker command and the
Android Intent contract are Phase B, and depend on signer-app support.
Tests: 31 new tests across the psbt/build/signers packages, anchored on the
BIP-341 wallet-test-vectors so the tweak, sighash, signature, and finalized
transaction are all checked against an authoritative source.
Still pending: Phase B (NIP-55 sign_psbt Intent) and Phase D (send UI +
broadcast + publish kind 8333).
Claude
a42b1e0f32