TYPE 0x0703 · COMPOUND FAMILY

HASH_SIG

Hash preimage verification combined with signature check in a single block. Collapses a hash + SIG two-block pattern, saving 8 bytes on wire.

Compound Non-Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
hash	HASH256	32 B	Conditions	SHA-256 hash the preimage must match. Node-computed — the user provides PREIMAGE and the node computes this field automatically. Raw hash input is rejected.
scheme	SCHEME	1 B	Conditions	Signature scheme identifier (0x01 = Schnorr, 0x02 = ECDSA). Routes to post-quantum verifier when PQ scheme set.
pubkey	PUBKEY	32-33 B	Witness	Public key matching the commitment
signature	SIGNATURE	64-65 B	Witness	Schnorr signature over the transaction
preimage	PREIMAGE	32 B	Witness	Data whose SHA-256 equals the hash field — provided by the user. The node derives HASH256 from this data at creation time.

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

Wire Format Breakdown

0x0703 0 3 HASH256 · 32B SCHEME · 1B Conditions = 73 bytes

0x0703 0 3 PUBKEY · 32B SIGNATURE · 64B PREIMAGE · 32B Witness = 138 bytes

Total 213 bytes (saves 8B vs separate blocks)

Evaluation Logic

1.Compute SHA256(PREIMAGE). If != HASH256 → UNSATISFIED

2.Verify witness PUBKEY against Merkle leaf (merkle_pub_key). If mismatch → UNSATISFIED

3.Verify SIGNATURE against PUBKEY. If invalid → UNSATISFIED

4.Both passed → SATISFIED

JSON Wire Format

Conditions

{
  "type": "HASH_SIG",
  "fields": [
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "HASH256", "hex": "e3b0c442...32 bytes" },
    { "type": "SCHEME", "hex": "01" }
  ]
}

Witness

{
  "type": "HASH_SIG",
  "fields": [
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "SIGNATURE", "hex": "30440...64 bytes" },
    { "type": "PREIMAGE", "hex": "deadbeef...32 bytes" }
  ]
}

Use Cases

Atomic Swap Claim Path

Counterparty reveals the hash preimage and signs in a single step. No timelock needed — the timeout path uses a separate TIMELOCKED_SIG rung.

Secret-Gated Signing

Require both knowledge of a secret (preimage) and possession of a private key. Neither alone is sufficient — dual-factor spending authorization.

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