The Evolution of Bitcoin: Unraveling the Meaning of OP_CHECKSIGVERIFY

Bitcoin’s underlying technology has undergone significant changes over the years, with each update building on the previous one. A notable example is the addition of multisig transactions in Bitcoin Cash (BCH). In this article, we’ll delve into why the opcode OP_CHECKSIGVERIFY was chosen as the first operation for multisig transactions and explore its implications.

Multisig Transactions: A Deep Dive

Multisignature transactions are a crucial feature in cryptocurrencies, as they allow multiple parties to agree to a transaction without being able to veto it. The most common implementation is the “one-of-one” (1-0-1) scheme, where only one of the signatures can be valid.

In 2018, Bitcoin Cash (BCH) was updated to include multisig transactions in its core protocol. This change introduced a new opcode: OP_CHECKSIGVERIFY.

The rationale behind OP_CHECKSIGVERIFY

OP_CHECKSIGVERIFY is not just a simple implementation of OP_CHECKSIG; it is actually the first step towards implementing true multi-signature functionality in Bitcoin Cash.

In traditional signatures, only one party can sign a transaction and check its outcome. This limitation limits cryptocurrency use cases that require multiple parties to co-sign transactions. In BCH, this problem is mitigated by introducing a hierarchical deterministic (HD) wallet system, which allows users to create complex wallets with multiple private keys.

The OP_CHECKSIGVERIFY opcode is responsible for validating the signature of each signer in the multisig transaction. It works as follows:

• The transaction input contains a list of signers and their private keys.

• Each signer submits their public key, which is verified by other signers.

• If a signer’s public key matches the expected one, they can proceed to sign the transaction using their private key.

OP_CHECKSIGVERIFY vs. OP_CHECKSIGVERIFY; OP_CHECKSIG

The OP_CHECKSIG opcode alone would only validate signatures from multiple signers without considering the specific requirements of the BCH multisig system. This leads to several issues:

• Inefficient validation

  

  : OP_CHECKSIG can be slow and resource-intensive, which could negatively impact the overall performance of BCH transactions.

• Lack of security: It does not provide any additional security features over traditional signatures.

The introduction of “OP_CHECKSIGVERIFY” addresses these concerns by providing a more secure and efficient way to validate multi-signature transactions in BCH. The use of hierarchical deterministic wallets ensures that multiple signers can co-sign transactions, while the OP_CHECKSIGVERIFY opcode provides robust signature verification mechanisms.

Conclusion

In conclusion, choosing “OP_CHECKSIGVERIFY” as the first operation for multisig transactions in Bitcoin Cash is a deliberate design decision aimed at improving the overall security and efficiency of BCH. By understanding the implications of this change, developers can better appreciate the innovative features that make Bitcoin Cash unique and attractive to users.

Sample code: OP_CHECKSIGVERIFY

To illustrate how OP_CHECKSIGVERIFY works, here is a Python example:

“`python

import hashlib

def verify_signature(signer_public_key, signature):

Use a secure hash function such as SHA-256

hash_signature = hashlib.sha256(str(signature).encode()).digest()

Extract the signer’s private key from his public key

private_key = signer_public_key.hex()

private_bytes = bytes.fromhex(private_key)

Compute the expected signature using the private key

expected_signature = hashlib.sha256(private_bytes).