TYPE 0x0901 · LEGACY FAMILY

P2PK_LEGACY

Legacy P2PK (pay-to-public-key) wrapped as a typed Ladder Script block. Same evaluation as SIG — Merkle leaf pubkey verified, then signature check. Closes arbitrary data surfaces.

Legacy Non-Invertible
Ladder Diagram
P2PK_LEGACY SIG VERIFY Delegates to EvalSigBlock internally
Fields
FieldData TypeSizeSideDescription
scheme SCHEME 1 B Conditions Signature scheme identifier (optional, 0x00 = Schnorr default)
pubkey PUBKEY 32-33 B Witness Public key (x-only 32B or compressed 33B)
signature SIGNATURE 64-65 B Witness Signature over the transaction sighash

Public key folded into Merkle leaf via merkle_pub_key (PubkeyCountForBlock = 1). No key field in conditions.

Wire Format Breakdown

Conditions side (committed in the rung leaf):

0x0901 0 1 SCHEME · 1B ≈ 7 bytes

Witness side (in input witness):

0x0901 0 2 PUBKEY · 33B SIGNATURE · 64B = 105 bytes
Total (conditions + witness) 144 bytes

With rung overhead included. Compressed pubkey (33B) case.

Evaluation Logic
1. Locate the witness PUBKEY and SIGNATURE; either missing → ERROR. Pubkey identity is bound at MLSC-proof level via merkle_pub_key — no leaf check here.
2. Read the optional conditions SCHEME (default Schnorr).
3. Dispatch VerifySigWithScheme(pubkey, sig, scheme, ...). Sig size checks fire here per the resolved scheme. Note: the legacy wrappers route through the Ladder LadderSigChecker, NOT Core's BaseSignatureChecker — handing a Schnorr sig to Core's checker would crash the process via three Taproot-only assertions in CheckSchnorrSignature (regression fix `83f3a99a25`).
4. The VerifySigWithScheme result is the block result — SATISFIED on valid sig, UNSATISFIED on verification failure, ERROR on malformed inputs.
Return Values
ConditionResult
Missing PUBKEY or SIGNATUREERROR
Merkle leaf verification failsUNSATISFIED
Signature failsUNSATISFIED
Signature validSATISFIED
JSON Wire Format
Conditions (committed in the rung leaf)
{
  "type": "P2PK_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "SCHEME", "hex": "01" }
  ]
}
Witness (input)
{
  "type": "P2PK_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "SIGNATURE", "hex": "e5f6a7...64 bytes" }
  ]
}
Notes
  • Delegates to EvalSigBlock internally. All signature schemes supported via SCHEME field.
  • Public key is folded into the Merkle leaf via merkle_pub_key. The user supplies PUBKEY and the node incorporates it into the leaf hash automatically.
  • Wraps legacy P2PK semantics — no new data surfaces.
  • All signature schemes (Schnorr, ECDSA, PQ) supported via the SCHEME routing field.
  • Closes the arbitrary data surface present in raw P2PK outputs.
Use Cases
Legacy P2PK Migration
Wrap existing P2PK outputs in typed Ladder blocks. Same spending semantics with anti-spam protection.
Composable Key Spending
Combine with timelocks, hash locks, or covenants on other rungs. Legacy key-spending with full Ladder Script composability.
← OUTPUT_CHECK P2PKH_LEGACY →