How to use Go language for blockchain wallet development?

With the continuous development and application of blockchain technology, blockchain wallets, as a management tool for digital assets, have become an area of ​​concern to more and more people, and have also become an important part of blockchain development. The security and ease of use of wallets are two core issues in blockchain applications. Today we will learn how to use Go language for blockchain wallet development, ensuring security without losing ease of use.

1. Basic knowledge of blockchain wallet

First of all, we need to understand what a blockchain wallet is. Relative to digital wallets in the traditional financial world, blockchain wallets refer more to an application for managing cryptocurrencies and digital assets. In blockchain, transactions are verified through digital signatures, and wallets are software that store private keys and create digital signatures. Therefore, security is the first element of a blockchain wallet, followed by ease of use.

2. Develop a simple blockchain wallet

In this article, we will use the Go language as an example to develop a blockchain wallet. We will build a simple blockchain wallet program with the following basic functions:

• Generate a public and private key pair
• Save the private key
• Import from the private key Public key
• Create transaction
• Sign transaction
• Broadcast transaction

2.1 Generate public and private key pair

Provided in Go language It has good support and can easily generate public and private key pairs. We can use the following command to generate a public and private key pair:

package main

import (
    "crypto/ecdsa"
    "crypto/rand"
    "crypto/x509"
    "encoding/hex"
    "encoding/pem"
    "errors"
    "fmt"
    "io/ioutil"
    "os"
)

func generateKeys() (*ecdsa.PrivateKey, error) {
    key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
    if err != nil {
        return nil, errors.New("generate keys error: " + err.Error())
    }

    file, err := os.Create("private.pem")
    if err != nil {
        return nil, errors.New("create private key file error: " + err.Error())
    }
    defer file.Close()

    err = pem.Encode(file, &pem.Block{
        Type:  "PRIVATE KEY",
        Bytes: x509.MarshalECPrivateKey(key),
    })
    if err != nil {
        return nil, errors.New("encode private key error: " + err.Error())
    }

    pub := key.PublicKey
    pubBytes, err := x509.MarshalPKIXPublicKey(&pub)
    if err != nil {
        return nil, errors.New("marshal public key error: " + err.Error())
    }

    pubStr := hex.EncodeToString(pubBytes)
    fmt.Println("public key: " + pubStr)

    return key, nil
}

The above command will generate a public and private key pair and save the private key to a local file. When generating a public-private key pair, the elliptic curve encryption algorithm is used, which has high security.

2.2 Import public key from private key

When we need to use the wallet next time, we can read the private key from the local file, calculate the public key, and save it to memory for subsequent use. The following is a code example for importing a public key from a private key:

package main

import (
    "crypto/ecdsa"
    "crypto/elliptic"
    "crypto/rand"
    "crypto/x509"
    "encoding/pem"
    "flag"
    "fmt"
    "io/ioutil"
    "os"
)

var privateKeyFile string
var publicKey *ecdsa.PublicKey

func init() {
    flag.StringVar(&privateKeyFile, "key", "private.pem", "private key file")
}

func main() {
    flag.Parse()

    key, err := readPrivateKeyFromFile(privateKeyFile)
    if err != nil {
        fmt.Println("read private key from file error:", err)
        return
    }

    publicKey = &key.PublicKey

    fmt.Println("public key:", publicKey)
}

func readPrivateKeyFromFile(filename string) (*ecdsa.PrivateKey, error) {
    data, err := ioutil.ReadFile(filename)
    if err != nil {
        return nil, err
    }

    block, _ := pem.Decode(data)
    if block == nil {
        return nil, fmt.Errorf("decode failed at %s", filename)
    }

    return x509.ParseECPrivateKey(block.Bytes)
}

2.3 Creating a transaction

In actual use, one of the main functions of the wallet is to create transactions. The following is a code example for creating a transfer transaction:

package main

import (
    "crypto/ecdsa"
    "crypto/rand"
    "crypto/sha256"
    "encoding/hex"
    "errors"
    "fmt"
    "math/big"
    "os"
)

type transaction struct {
    senderPrivateKey *ecdsa.PrivateKey
    recipient        string
    amount           *big.Int
}

func newTransaction(senderPrivateKey *ecdsa.PrivateKey, recipient string, amount *big.Int) (*transaction, error) {
    if senderPrivateKey == nil {
        return nil, errors.New("`senderPrivateKey` is nil")
    }

    if recipient == "" {
        return nil, errors.New("`recipient` is empty")
    }

    if amount == nil || amount.Cmp(big.NewInt(0)) <= 0 {
        return nil, errors.New("`amount` is invalid")
    }

    return &transaction{
        senderPrivateKey: senderPrivateKey,
        recipient:        recipient,
        amount:           amount,
    }, nil
}

func (t *transaction) sign() (string, error) {
    if t.senderPrivateKey == nil {
        return "", errors.New("`senderPrivateKey` is nil")
    }

    hash := sha256.Sum256([]byte(fmt.Sprintf("%s%s%d", t.senderPrivateKey.PublicKey.X.String(), t.senderPrivateKey.PublicKey.Y.String(), t.amount)))

    r, s, err := ecdsa.Sign(rand.Reader, t.senderPrivateKey, hash[:])
    if err != nil {
        return "", errors.New("sign error: " + err.Error())
    }

    sig := r.String() + "," + s.String()

    return sig, nil
}

In the above code, we use SHA-256 for hash calculation and the ECDSA algorithm to sign the transaction to ensure the security of the transaction.

2.4 Broadcast Transaction

After creating and signing the transaction, we need to broadcast it to the blockchain network so that any node in the entire network can see and verify the transaction. The following is a code example of a broadcast transaction:

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "net/http"
    "net/url"
)

type client struct {
}

func newClient() *client {
    return &client{}
}

func (c *client) post(url string, data url.Values) ([]byte, error) {
    res, err := http.PostForm(url, data)
    if err != nil {
        return nil, err
    }

    defer res.Body.Close()

    content, err := ioutil.ReadAll(res.Body)
    if err != nil {
        return nil, err
    }

    return content, nil
}

func (c *client) broadcastTransaction(tx *transaction) (string, error) {
    data := url.Values{}
    data.Add("sender_public_key", tx.senderPrivateKey.PublicKey.X.String()+tx.senderPrivateKey.PublicKey.Y.String())
    data.Add("recipient", tx.recipient)
    data.Add("amount", tx.amount.String())

    sig, err := tx.sign()
    if err != nil {
        return "", err
    }

    data.Add("signature", sig)

    content, err := c.post("http://localhost:8080/api/transactions", data)
    if err != nil {
        return "", err
    }

    var result struct {
        Success bool   `json:"success"`
        Message string `json:"message"`
    }

    err = json.Unmarshal(content, &result)
    if err != nil {
        return "", err
    }

    if result.Success {
        return result.Message, nil
    }

    return "", fmt.Errorf("broadcast error: %s", result.Message)
}

During the broadcast transaction, we send the transaction content to the nodes in the network and wait for responses from other nodes. Due to the P2P nature of the blockchain network, we need to ensure that transactions can be verified and identified by other nodes.

3. Summary

Through the introduction of this article, we can see that using Go language for blockchain wallet development is both interesting and challenging. When developing a wallet, we need to consider both security and ease of use so that the wallet can be accepted and used by more people. Therefore, we need to pay attention to enhancing the stability, reliability, ease of maintenance, etc. of the code during the development process. In future applications and development, we also need to pay more attention to the social impact and development of blockchain and continue to support its application and promotion.

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