TYPE 0x0907 · LEGACY FAMILY

P2TR_SCRIPT_LEGACY

Legacy P2TR script-path (Taproot) wrapped as a typed Ladder Script block. This is the critical block — taproot script-path is the primary inscription/data-embedding vector today. The revealed script leaf must be valid Ladder Script conditions.

Legacy Non-Invertible
Ladder Diagram
P2TR_SCRIPT_LEGACY MERKLE + INNER EVAL Closes the taproot inscription vector
Fields
FieldData TypeSizeSideDescription
hash256 HASH256 32 B Conditions Merkle root of the script tree. Node-computed — the node derives this from the PREIMAGE (script leaf). Raw hash input is rejected.
preimage PREIMAGE var Witness Revealed script leaf (serialised Ladder Script conditions) — provided by the user. The node derives HASH256 from this data at creation time.
[inner witness] var var Witness Witness fields required to satisfy the revealed leaf conditions

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):

0x0907 0 1 HASH256 · 32B = 38 bytes

Witness side (in input witness):

0x0907 0 n PREIMAGE · varB [inner witness fields] = variable
Total (conditions + witness) variable

Witness size depends on the revealed script leaf and its witness fields.

Evaluation Logic
1. Locate HASH256 and PREIMAGE (or SCRIPT_BODY as a fallback). Either missing → ERROR. HASH256 not exactly 32 B → ERROR
2. Single-leaf model: compute SHA256(PREIMAGE) directly and memcmp against the committed HASH256. Mismatch → UNSATISFIED. (For deeper script trees the user must commit a structure that hashes down to a single leaf at this layer; multi-leaf taproot expansion is not implemented in the wrapper.)
3. Recurse into EvalInnerConditions(PREIMAGE, depth+1): deserialize, enforce MAX_LEGACY_INNER_DEPTH = 2, audit-E-020 witness-stack exact-count guard, evaluate inner rungs with OR logic.
Return Values
ConditionResult
Missing HASH256 or PREIMAGEERROR
SHA256(PREIMAGE) != HASH256 (Merkle root)UNSATISFIED
PREIMAGE fails to deserialize as Ladder conditionsERROR
Inner conditions evaluation failsUNSATISFIED
Recursion depth > 2ERROR
Inner conditions satisfiedSATISFIED
JSON Wire Format
Conditions (committed in the rung leaf)
{
  "type": "P2TR_SCRIPT_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "HASH256", "hex": "e3b0c4...32 bytes (Merkle root)" }
  ]
}
Witness (input)
{
  "type": "P2TR_SCRIPT_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "PREIMAGE", "hex": "01020304...serialised Ladder conditions (revealed leaf)" },
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "SIGNATURE", "hex": "e5f6a7...64 bytes" }
  ]
}
Notes
  • Closes the taproot inscription vector — the primary data-embedding surface in Bitcoin today.
  • Revealed script leaf must deserialize as valid Ladder Script conditions. Arbitrary data is rejected.
  • HASH256 is node-computed: the user provides PREIMAGE (script leaf) and the node derives the hash automatically. PUBKEY (internal key) is folded into the Merkle leaf via merkle_pub_key. Submitting raw hash values directly is rejected.
  • Recursion depth limited to 2.
  • The internal key is folded into the Merkle leaf, used for key-path/script-path binding.
  • For key-path-only spending, see P2TR_LEGACY (0x0906).
Use Cases
Anti-Inscription Protection
The primary inscription/data-embedding vector (taproot script-path) is closed. Revealed script leaf MUST be valid Ladder conditions.
Script Tree Migration
Taproot script tree with typed Ladder leaves instead of arbitrary scripts. Full anti-spam coverage.
← P2TR_LEGACY QABI_PRIME →