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fix on OP_CHECKMULTISIG per #606

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Shannon Appelcline 2026-01-15 13:55:14 -10:00
parent 0649608832
commit e65dc59429
No known key found for this signature in database
2 changed files with 19 additions and 17 deletions
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4
10_2_Building_the_Structure_of_P2SH.md
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@ -106,9 +106,9 @@ Here's what the individual parts mean:
* 0x52 = OP_2
* 0x21 = OP_PUSHDATA 33 bytes (hex: 0x21)
* 0x02da2f10746e9778dd57bd0276a4f84101c4e0a711f9cfd9f09cde55acbdd2d191 = the next 33 bytes (public-key hash)
* 0x02da2f10746e9778dd57bd0276a4f84101c4e0a711f9cfd9f09cde55acbdd2d191 = the next 33 bytes (public key)
* 0x21 = OP_PUSHDATA 33 bytes (hex: 0x21)
* 0x02bfde48be4aa8f4bf76c570e98a8d287f9be5638412ab38dede8e78df82f33fa3 = the next 33 bytes (public-key hash)
* 0x02bfde48be4aa8f4bf76c570e98a8d287f9be5638412ab38dede8e78df82f33fa3 = the next 33 bytes (public key)
* 0x52 = OP_2
* 0xae = OP_CHECKMULTISIG

32
10_4_Scripting_a_Multisig.md
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@ -4,17 +4,19 @@ Before we close out this intro to P2SH scripting, it's worth examining a more re
## Understand the Multisig Code
Multisig transactions are created in Bitcoin using the `OP_CHECKMULTISIG` code. `OP_CHECKMULTISIG` expects a long string of arguments that looks like this: `0 ... sigs ... <m> ... addresses ... <n> OP_CHECKMULTISIG`. When `OP_CHECKMULTISIG` is run, it does the following:
Multisig transactions are created in Bitcoin using the `OP_CHECKMULTISIG` code. `OP_CHECKMULTISIG` expects a long string of arguments that looks like this: `0 ... sigs ... <m> ... public keys ... <n> OP_CHECKMULTISIG`. When `OP_CHECKMULTISIG` is run, it does the following:
1. Pop the first value from the stack (`<n>`).
2. Pop "n" values from the stack as Bitcoin addresses (hashed public keys).
2. Pop "n" values from the stack as public keys.
3. Pop the next value from the stack (`<m>`).
4. Pop "m" values from the stack as potential signatures.
5. Pop a `0` from the stack due to a mistake in the original coding.
6. Compare the signatures to the Bitcoin adddresses.
6. Compare the signatures to the public keys.
7. Push a `True` or `False` depending on the result.
The operands of `OP_MULTISIG` are typically divided, with the `0` and the signatures coming from the unlocking script and the "m", "n", and addresses being detailed by the locking script.
The operands of `OP_MULTISIG` are typically divided, with the `0` and
the signatures coming from the unlocking script and the "m", "n", and
public keys being detailed by the locking script.
The requirement for that `0` as the first operand for `OP_CHECKMULTISIG` is a consensus rule. Because the original version of `OP_CHECKMULTISIG` accidentally popped an extra item off the stack, Bitcoin must forever follow that standard, lest complex redemption scripts from that time period accidentally be broken, rendering old funds unredeemable.
@ -24,11 +26,11 @@ The requirement for that `0` as the first operand for `OP_CHECKMULTISIG` is a co
As discussed in [§10.1: Understanding the Foundation of P2SH](10_1_Understanding_the_Foundation_of_P2SH.md), multisigs are one of the standard Bitcoin transaction types. A transaction can be created with a locking script that uses the raw `OP_CHECKMULTISIG` command, and it will be accepted into a block. This is the classic methodology for using multisigs in Bitcoin.
As an example, we will revisit the multisig created in [§6.1](06_1_Sending_a_Transaction_to_a_Multisig.md) one final time and build a new locking script for it using this methodology. As you may recall, that was a 2-of-2 multisig built from `$address1` and `$address2`.
As an example, we will revisit the multisig created in [§6.1](06_1_Sending_a_Transaction_to_a_Multisig.md) one final time and build a new locking script for it using this methodology. As you may recall, that was a 2-of-2 multisig built from `$pubkey1` and `$pubkey2`.
As `OP_CHECKMULTISIG` locking script requires the "m" (`2`), the addresses, and the "n" (`2`), you could write the following `scriptPubKey`:
As `OP_CHECKMULTISIG` locking script requires the "m" (`2`), the public keys, and the "n" (`2`), you could write the following `scriptPubKey`:
```
2 $address1 $address2 2 OP_CHECKMULTISIG
2 $pubkey1 $pubkey2 2 OP_CHECKMULTISIG
```
If this looks familiar, that's because it's the multisig that you deserialized in [§10.2: Building the Structure of P2SH](10_2_Building_the_Structure_of_P2SH.md).
```
@ -48,20 +50,20 @@ The `scriptSig` for a standard multisig address must then submit the missing ope
In order to spend a multisig UTXO, you run the `scriptSig` and `scriptPubKey` as follows:
```
Script: 0 $signature1 $signature2 2 $address1 $address2 2 OP_CHECKMULTISIG
Script: 0 $signature1 $signature2 2 $pubkey1 $pubkey2 2 OP_CHECKMULTISIG
Stack: [ ]
```
First, you place all the constants on the stack:
```
Script: OP_CHECKMULTISIG
Stack: [ 0 $signature1 $signature2 2 $address1 $address2 2 ]
Stack: [ 0 $signature1 $signature2 2 $pubkey1 $pubkey2 2 ]
```
Then, the `OP_CHECKMULTISIG` begins to run. First, the "2" is popped:
```
Running: OP_CHECKMULTISIG
Stack: [ 0 $signature1 $signature2 2 $address1 $address2 ]
Stack: [ 0 $signature1 $signature2 2 $pubkey1 $pubkey2 ]
```
Then, the "2" tells `OP_CHECKMULTISIG `to pop two addresses:
Then, the "2" tells `OP_CHECKMULTISIG `to pop two public keys:
```
Running: OP_CHECKMULTISIG
Stack: [ 0 $signature1 $signature2 2 ]
@ -81,7 +83,7 @@ Then, one more item is mistakenly popped:
Running: OP_CHECKMULTISIG
Stack: [ ]
```
Then, `OP_CHECKMULTISIG` completes its operation by comparing the "m" signatures to the "n" addresses:
Then, `OP_CHECKMULTISIG` completes its operation by comparing the "m" signatures to the "n" public keys:
```
Script:
Stack: [ True ]
@ -105,7 +107,7 @@ P2SH multisigs are the modern methodology for creating multisigs on the Blockcha
To create a P2SH multisig, follow the standard steps for creating a P2SH locking script:
1. Serialize `2 $address1 $address2 2 OP_CHECKMULTISIG`.
1. Serialize `2 $pubkey1 $pubkey2 2 OP_CHECKMULTISIG`.
1. `<serializedMultiSig>` = "522102da2f10746e9778dd57bd0276a4f84101c4e0a711f9cfd9f09cde55acbdd2d1912102bfde48be4aa8f4bf76c570e98a8d287f9be5638412ab38dede8e78df82f33fa352ae"
2. Save `<serializedMultiSig>` for future reference as the redeemScript.
1. `<redeemScript>` = "522102da2f10746e9778dd57bd0276a4f84101c4e0a711f9cfd9f09cde55acbdd2d1912102bfde48be4aa8f4bf76c570e98a8d287f9be5638412ab38dede8e78df82f33fa352ae"
@ -133,9 +135,9 @@ To unlock the P2SH multisig, first confirm the script:
Then, run the multisig script:
1. Deserialize `<serializedMultiSig>` to `2 $address1 $address2 2 OP_CHECKMULTISIG`.
1. Deserialize `<serializedMultiSig>` to `2 $pubkey1 $pubkey2 2 OP_CHECKMULTISIG`.
2. Concatenate that with the earlier operands in the unlocking script, `0 $signature1 $signature2`.
3. Validate `0 $signature1 $signature2 2 $address1 $address2 2 OP_CHECKMULTISIG`.
3. Validate `0 $signature1 $signature2 2 $pubkey1 $pubkey2 2 OP_CHECKMULTISIG`.
4. Succeed if the operands fulfill the deserialized `redeemScript`.
Now you know how the multisig transaction in [§6.1](06_1_Sending_a_Transaction_to_a_Multisig.md) was actually created, how it was validated for spending, and why that `redeemScript` was so important.