# Multisignature Verification: Shared Control

Multisignature scripts require **multiple signatures** from different parties to authorize spending, enabling applications like joint accounts, escrow services, and corporate treasuries.

#### OP\_CHECKMULTISIG: Multiple Signature Verification

| Opcode            | Input                                         | Output       | Description                                                                    |
| ----------------- | --------------------------------------------- | ------------ | ------------------------------------------------------------------------------ |
| OP\_CHECKMULTISIG | x sig1 sig2 ... \<n> pubkey1 pubkey2 ... \<m> | TRUE / FALSE | Verifies that at least M signatures match public keys from the N provided keys |

**Critical ordering requirement:** Signatures must appear in the same order as their corresponding public keys.

**The "Multisig Bug":** Due to an off-by-one error, OP\_CHECKMULTISIG removes one extra value from the stack. Script spenders must add a dummy value (typically OP\_0) before the signatures.

**Example: 2-of-3 Multisig**

```
OP_0 <sig1> <sig2> OP_2 <pubkey1> <pubkey2> <pubkey3> OP_3 OP_CHECKMULTISIG
```

This requires any 2 signatures from 3 possible signers—commonly used for escrow (buyer, seller, arbiter).


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