TYPE 0x0906 · LEGACY FAMILY

P2TR_LEGACY

Legacy P2TR key-path (Taproot) wrapped as a typed Ladder Script block. Key-path spend — same evaluation as SIG block. Closes key-path data surfaces.

Legacy Non-Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
scheme	SCHEME	1 B	Conditions	Signature scheme identifier (optional, Schnorr default)
pubkey	PUBKEY	32 B	Witness	X-only public key (Taproot key-path)
signature	SIGNATURE	64-65 B	Witness	Schnorr 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):

0x0906 0 1 SCHEME · 1B ≈ 7 bytes

Witness side (in input witness):

0x0906 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.

2. Read the optional conditions SCHEME (default Schnorr).

3. Dispatch VerifySigWithScheme(pubkey, sig, scheme, ...) through the Ladder LadderSigChecker. The result is the block result.

Return Values

Condition	Result
Missing PUBKEY or SIGNATURE	ERROR
Signature size out of range for the resolved scheme	ERROR
Signature verification fails	UNSATISFIED
Signature valid	SATISFIED

JSON Wire Format

Conditions (committed in the rung leaf)

{
  "type": "P2TR_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "SCHEME", "hex": "01" }
  ]
}

Witness (input)

{
  "type": "P2TR_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "SIGNATURE", "hex": "e5f6a7...64 bytes" }
  ]
}

Notes

Key-path only — for script-path see P2TR_SCRIPT_LEGACY (0x0907).
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.
Delegates to EvalSigBlock internally.
Closes key-path data surfaces while preserving Taproot's key-path efficiency.

Use Cases

Taproot Key-Path Migration

Wraps taproot key-path spends. For script-path, see P2TR_SCRIPT_LEGACY.

PQ-Ready Key Path

Key-path spend with SCHEME field enabling post-quantum signature migration.

← P2WSH_LEGACY P2TR_SCRIPT_LEGACY →