golang builds blockchain

The concept of blockchain has received worldwide attention and heated discussions since the release of the Bitcoin white paper in 2008. Its core value is decentralization and immutability. In recent years, with the deepening of people's understanding of blockchain technology and the development of the open source community, using golang to build blockchain has become more and more popular.

Golang is a programming language developed by Google. It has the advantages of efficiency, simplicity, security, etc., and supports multi-threading and garbage collection. The features of this language are ideal for developing distributed systems and demonstrate excellent performance in a variety of scenarios. In this article, we will introduce how to use golang to build a blockchain.

1. Overview

The core technology of blockchain is actually very simple, mainly composed of decentralization, consensus algorithm, block data structure, blockchain storage and encryption, etc. Among them, the storage and encryption of the blockchain use hash algorithm.

In golang, we can use golang's hash algorithm library for implementation. For example, we can use the crypto/sha256 library to complete the hash calculation and the encoding/hex library to convert the hash value to a hexadecimal string. Such an implementation is not only highly efficient, but also ensures high reliability of the hash value.

2. Data structure

We define a blockchain to contain multiple blocks, and each block contains four pieces of information:

1. BlockHeader ): Contains the previous block (PrevBlockHash), timestamp (TimeStamp), and the hash value of the current block (Hash).
2. Transaction information (Transaction): consists of one or more transactions.
3. Block height (Height): Indicates the height of the current block in the entire blockchain.
4. Difficulty value (Difficulty): used to determine whether the consensus algorithm meets the requirements.

In golang, we can use the following structure to represent a block:

type Block struct {
  BlockHeader BlockHeader
  Transaction []Transaction
}

type BlockHeader struct {
  PrevBlockHash []byte
  TimeStamp int64
  Hash []byte
}

type Transaction struct {
  Data []byte
}

Among them, []byte represents binary data. Transaction information can be defined according to specific needs.

3. Blockchain Storage

Since the blockchain is a distributed system, all participants need to know the status of the entire blockchain. Therefore, we need to store the blockchain in a distributed database.

In golang, we can use databases such as LevelDB or RocksDB for storage. These databases are lightweight key-value databases that support high concurrency and high throughput. At the same time, they support loading data from the hard disk or memory, and can automatically perform data compression and garbage collection.

When using these databases, we need to store the blocks in the database according to the hash value of the block as the key. At the same time, we need to record the hash value and height of the longest branch (LongestChain) of the current blockchain to facilitate the implementation of the consensus algorithm.

type BlockChain struct {
  blocks []*Block
  db     *leveldb.DB
  LongestChainHash []byte // 最长分支的哈希值
  LongestChainHeight int   // 最长分支的高度
}

4. Consensus Algorithm

The consensus algorithm of the blockchain is the core of ensuring the security of the blockchain. Common consensus algorithms include Proof-of-Work ("Proof of Work") and Proof-of-Stake ("Proof of Stake").

In this article, we only introduce the implementation of the Proof-of-Work algorithm. The Proof-of-Work algorithm requires participants to perform a large number of hash calculations and requires the calculation results to meet certain conditions. If the conditions are met, the block mined by the node is broadcast to the entire network, and other nodes verify and update their status. In this way, even if there is collusion between nodes, the entire network cannot be deceived due to differences in computing power.

The specific implementation process is as follows:

1. Initially, record the hash value and height of the longest branch.
2. When a node mines a new block and broadcasts it to the entire network, other nodes will first perform some basic verification after receiving it (such as whether the hash of the previous block is correct), and then verify the current block. .
3. The verification process is to hash the hash value of the current block and compare it with the difficulty value. If the calculated hash value is less than the difficulty value, it means that the node's workload meets the requirements and the new block can be added to its own blockchain. Otherwise, the node will be rejected by other nodes and marked as an invalid node.
4. After receiving a new block, in order to ensure the security of the blockchain, the node will verify the current block together with the blocks it depends on. If the block it depends on is invalid, the current block will also be marked as invalid.

The specific implementation can be carried out through the following code:

func (bc *BlockChain) AddBlock(b *Block) bool {
  if !bc.isValidBlock(b) {
    return false
  }
  bc.db.Put(b.Hash, []byte(b.Encode()))
  if b.BlockHeader.TimeStamp > bc.blocks[bc.LongestChainHeight-1].BlockHeader.TimeStamp {
    bc.LongestChainHash = b.Hash
    bc.LongestChainHeight = bc.blocks[bc.LongestChainHeight-1].BlockHeader.Height + 1
  }
  bc.blocks = append(bc.blocks, b)
  return true
}

func (bc *BlockChain) isValidBlock(b *Block) bool {
  prevBlock := bc.getPrevBlock(b)
  if prevBlock == nil {
    return false
  }
  if !isValidHash(b.Hash) {
    return false
  }
  if b.BlockHeader.TimeStamp <= prevBlock.BlockHeader.TimeStamp {
    return false
  }
  if !isValidProofOfWork(b) {
    return false
  }
  return true
}

func (bc *BlockChain) getPrevBlock(b *Block) *Block {
  if len(bc.blocks) == 0 {
    return nil
  }
  lastBlock := bc.blocks[len(bc.blocks)-1]
  if lastBlock.BlockHeader.Hash == b.BlockHeader.PrevBlockHash {
    return lastBlock
  }
  return nil
}

func isValidProofOfWork(b *Block) bool {
  hash := sha256.Sum256(b.Encode())
  target := calculateTarget()
  return hash[:4] == target
}

In actual applications, complex situations such as forks and malicious attacks also need to be considered. This is only introduced as a basic implementation method. In actual applications, further optimization needs to be carried out according to your own needs.

5. Summary

This article introduces the basic process of using golang to build a blockchain, including data structure, blockchain storage and consensus algorithm. In practical applications, it is also necessary to strengthen the understanding of distributed systems and ensure the security of the blockchain while ensuring performance. At the same time, golang's efficiency and reliability also provide us with more choices.

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