TYPE 0x0002 · SIGNATURE FAMILY

MULTISIG

M-of-N threshold signature verification. Multiple pubkey commitments are locked in conditions with a threshold. The witness provides N pubkeys and M valid signatures to satisfy the block.

Signature Non-Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
threshold	NUMERIC	1-4 B	Conditions	Required number of valid signatures (M)
pubkey[0..N]	PUBKEY	32-33 B each	Witness	All N public keys (x-only 32B or compressed 33B)
signature[0..M]	SIGNATURE	64-65 B each	Witness	M valid signatures corresponding to M distinct pubkeys
scheme	SCHEME	1 B	Witness (opt)	Optional PQ signature scheme identifier for post-quantum routing

Public keys folded into Merkle leaf via merkle_pub_key (PubkeyCountForBlock = N). No key fields in conditions.

Wire Format Breakdown

Conditions side (example 2-of-3):

0x0002 0 4 NUMERIC · 3B COMMIT · 32B COMMIT · 32B COMMIT · 32B = 111 bytes

Witness side (example 2-of-3):

0x0002 0 5 PK · 32B PK · 32B PK · 32B SIG · 64B SIG · 64B = 238 bytes

Total (conditions + witness, 2-of-3) 351 bytes

Wire size scales linearly: N pubkey commits in conditions + N pubkeys + M signatures in witness.

Evaluation Logic

1. Read threshold M from NUMERIC field. If M < 1 or M > N → ERROR

2. Verify each witness PUBKEY against Merkle leaf (merkle_pub_key). If any key fails verification → UNSATISFIED

3. For each SIGNATURE, try each unused pubkey. On valid match, increment valid_count and mark pubkey used.

4. If valid_count ≥ M → SATISFIED. Otherwise → UNSATISFIED

Return Values

Condition	Result
Missing NUMERIC field or Merkle leaf pubkey count mismatch	ERROR
Threshold M < 1 or M > N	ERROR
Fewer than N pubkeys in witness	ERROR
Merkle leaf verification fails for any key	UNSATISFIED
Fewer than M valid signatures	UNSATISFIED
M or more valid signatures from distinct keys	SATISFIED

JSON Wire Format

Conditions (scriptPubKey, 2-of-3 example)

{
  "type": "MULTISIG",
  "inverted": false,
  "fields": [
    { "type": "NUMERIC", "value": 2 },
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "PUBKEY", "hex": "03def2...33 bytes" },
    { "type": "PUBKEY", "hex": "02789a...33 bytes" }
  ]
}

Witness (input, 2-of-3 example)

{
  "type": "MULTISIG",
  "inverted": false,
  "fields": [
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "PUBKEY", "hex": "03def2...33 bytes" },
    { "type": "PUBKEY", "hex": "02789a...33 bytes" },
    { "type": "SIGNATURE", "hex": "30440...64 bytes" },
    { "type": "SIGNATURE", "hex": "e5f71...64 bytes" }
  ]
}

Use Cases

Multi-Party Escrow

A 2-of-3 MULTISIG where buyer, seller, and arbitrator each hold a key. Any two parties can release funds, enabling trustless escrow with dispute resolution.

Corporate Treasury

Organizational funds protected by M-of-N threshold policy. Requires multiple officers to authorize spending, preventing single-point-of-compromise theft.

Backup Key Schemes

A 1-of-3 setup where the primary key, a hardware wallet backup, and a social recovery key can each independently spend. Prevents permanent loss from any single key compromise or loss.

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