Go语言中实现MD5-based分组密码：安全性考量与现代加密实践

package main

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/rand"
    "encoding/hex"
    "fmt"
    "io"
    "log"
)

// Encrypt 使用AES-GCM加密数据
func Encrypt(key, plaintext []byte) ([]byte, error) {
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }

    gcm, err := cipher.NewGCM(block)
    if err != nil {
        return nil, err
    }

    nonce := make([]byte, gcm.NonceSize())
    if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
        return nil, err
    }

    // 将nonce作为前缀添加到密文，方便解密时提取
    ciphertext := gcm.Seal(nonce, nonce, plaintext, nil)
    return ciphertext, nil
}

// Decrypt 使用AES-GCM解密数据
func Decrypt(key, ciphertext []byte) ([]byte, error) {
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }

    gcm, err := cipher.NewGCM(block)
    if err != nil {
        return nil, err
    }

    nonceSize := gcm.NonceSize()
    if len(ciphertext) < nonceSize {
        return nil, fmt.Errorf("ciphertext too short")
    }

    nonce, encryptedMessage := ciphertext[:nonceSize], ciphertext[nonceSize:]
    plaintext, err := gcm.Open(nil, nonce, encryptedMessage, nil)
    if err != nil {
        return nil, err
    }
    return plaintext, nil
}

func main() {
    // 32字节密钥 (AES-256)
    key := make([]byte, 32)
    if _, err := io.ReadFull(rand.Reader, key); err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Key: %s\n", hex.EncodeToString(key))

    plaintext := []byte("This is a secret message to be encrypted.")
    fmt.Printf("Original: %s\n", string(plaintext))

    encrypted, err := Encrypt(key, plaintext)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Encrypted: %s\n", hex.EncodeToString(encrypted))

    decrypted, err := Decrypt(key, encrypted)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Decrypted: %s\n", string(decrypted))

    if string(plaintext) != string(decrypted) {
        log.Fatal("Decryption failed: plaintext does not match original")
    }
}

// 这是一个概念性的示例，不代表完整的PHP MD5-based cipher
// 实际转换需要根据PHP代码的精确逻辑进行
package main

import (
    "crypto/md5"
    "fmt"
)

// simulatePHP_MD5_CipherBlock 模拟PHP MD5-based分组密码的一个块操作
// 假设：密钥是字符串，每个块的密钥流通过MD5(key + block_index)生成
func simulatePHP_MD5_CipherBlock(key string, block []byte, blockIndex int) ([]byte, error) {
    // 模拟PHP中将key和block_index组合生成哈希输入
    keyMaterial := []byte(fmt.Sprintf("%s%d", key, blockIndex))

    h := md5.New()
    h.Write(keyMaterial)
    keyStream := h.Sum(nil) // 16字节MD5哈希作为密钥流

    if len(block) > len(keyStream) {
        return nil, fmt.Errorf("block size exceeds key stream size (16 bytes)")
    }

    encryptedBlock := make([]byte, len(block))
    for i := 0; i < len(block); i++ {
        encryptedBlock[i] = block[i] ^ keyStream[i]
    }
    return encryptedBlock, nil
}

func main() {
    phpKey := "mysecretkey"
    dataBlock := []byte("hello world block 1")

    // 模拟加密第一个块
    encrypted, err := simulatePHP_MD5_CipherBlock(phpKey, dataBlock, 0)
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
    fmt.Printf("Encrypted block: %x\n", encrypted)

    // 模拟解密第一个块
    decrypted, err := simulatePHP_MD5_CipherBlock(phpKey, encrypted, 0) // 解密是再次异或
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
    fmt.Printf("Decrypted block: %s\n", decrypted)
}