What are opcodes in Bitcoin?

In the context of general purpose computers, an opcode, short for “operation code,” is a fundamental component of computer programming and assembly language. It represents a specific instruction that a computer’s central processing unit (CPU) can execute. Opcodes are essential for telling the CPU what operation to perform, such as arithmetic calculations, data manipulation, memory access, and control flow.

In the context of Bitcoin scripting and smart contracts, opcodes are used to define the individual steps that make up a transaction script. Bitcoin’s scripting language is a stack-based language, which means that opcodes manipulate data on a stack, executing various operations to achieve specific outcomes. Bitcoin scripting is primarily used for defining conditions that must be met for spending funds (e.g., requiring a cryptographic signature) and enabling complex contract functionality.

However, it’s important to note that Bitcoin’s scripting language is intentionally limited and conservative to ensure security and prevent potential vulnerabilities. As a result, some opcodes are disabled or restricted to maintain the network’s stability and reduce the risk of unintended behaviours.

Opcodes play a crucial role in defining the rules and conditions for spending and managing Bitcoin transactions, allowing for both simple and more complex transaction scripting on Bitcoin.

The Lightning Network primarily uses a subset of Bitcoin’s existing opcodes. The Lightning Network’s design relies on a combination of Bitcoin’s scripting capabilities and the concept of Hash Time-Locked Contracts (HTLCs) to enable off-chain transactions and payment channels.

While the Lightning Network doesn’t introduce new opcodes, it utilises several key opcodes to create the necessary conditions for secure and trustless payment routing through payment channels. Some of the important opcodes used in LN include:

These opcodes, in combination with payment channel mechanisms and Hash Time-Locked Contracts, enable the Lightning Network to facilitate secure and fast off-chain transactions. Keep in mind that while these opcodes are essential for the Lightning Network’s operation, the specific ways they are used might vary depending on the Lightning Network implementation and its associated protocols.