P2MS (bare multisig)

Bare m-of-n multisig. The locking script lists n public keys directly; any m valid signatures unlock it. Distinct from P2SH-wrapped multisig — the keys are in the locking script itself.

name	p2ms
category	locking_script
family	payment
status	stable

ASM Pattern

OP_   ...  OP_ OP_CHECKMULTISIG

Hex Pattern

5  5 ae

Fields

Name	Type	Size	Description
m	integer	1	Threshold. Number of valid signatures required (1–16). Encoded as OP_1..OP_16 (0x51..0x60).
pubkeys	list	n × 33 or 65	The n candidate public keys, each pushed individually. Order matters — signatures must be provided in the same order.
n	integer	1	Total key count (m ≤ n ≤ 16). Encoded as OP_1..OP_16.

Detector

method	opcode_sequence
rule	script[0] in 0x51..0x60 # OP_1..OP_16 (m) && script[-1] == 0xae # OP_CHECKMULTISIG && script[-2] in 0x51..0x60 # OP_1..OP_16 (n) && interior pushes count == n
confidence	medium

Unlocking script

OP_0 <signature_1> <signature_2> ... <signature_m>

The leading OP_0 is the well-known off-by-one workaround for OP_CHECKMULTISIG, which pops one extra item from the stack.

Notes

Bare P2MS is less common than P2SH-wrapped multisig on BTC but remains present on BSV. The detector confidence is medium because non-standard scripts can incidentally start with OP_<n> and end with OP_CHECKMULTISIG without being well-formed multisig; a full parser should verify that the interior pushes are valid pubkey encodings.