Exercise 2: Hard

In this exercise, you will be working with a Bitcoin P2MS (Pay-to-Multisig) ScriptPubKey.

Your task is to complete the decompileP2MSScriptPubKey function, which decompiles a hex-encoded ScriptPubKey and extracts the number of required signatures and the associated public keys.

Follow the hints provided if you get stuck, and test your code by entering a ScriptPubKey hex string in the input field below.

Once you've completed the function, you can compare your solution with the provided answer.

Click to reveal next hint (0/6)

Start by iterating over each byte in the `scriptPubKeyHex` string. You’ll need to determine whether the byte represents an opcode or data.
For opcodes between 0x01 and 0x4b, you should treat the byte as the length of the data that follows.
Extract the data by slicing the scriptPubKey buffer and increment the index `i` appropriately.
Check if the last byte in the script is the `OP_CHECKMULTISIG` opcode (0xae). If it's not, throw an error.
Subtract 0x50 from the first byte to get the number of required signatures.
The remaining data elements between the first and last opcodes are the public keys. Convert them to hex strings.

Solution code

In this exercise, you will be working with a Bitcoin P2MS (Pay-to-Multisig) ScriptPubKey.

Your task is to complete the decompileP2MSScriptPubKey function, which decompiles a hex-encoded ScriptPubKey and extracts the number of required signatures and the associated public keys.

Follow the hints provided if you get stuck, and test your code by entering a ScriptPubKey hex string in the input field below.

Once you've completed the function, you can compare your solution with the provided answer.

Click to reveal next hint (0/6)

Start by iterating over each byte in the `scriptPubKeyHex` string. You’ll need to determine whether the byte represents an opcode or data.
For opcodes between 0x01 and 0x4b, you should treat the byte as the length of the data that follows.
Extract the data by slicing the scriptPubKey buffer and increment the index `i` appropriately.
Check if the last byte in the script is the `OP_CHECKMULTISIG` opcode (0xae). If it's not, throw an error.
Subtract 0x50 from the first byte to get the number of required signatures.
The remaining data elements between the first and last opcodes are the public keys. Convert them to hex strings.