golang crypt包的AES加密函数的使用

golang AES加密函数的使用

1. 什么是AES

AES： Advanced Encryption Standard

高阶加密标准，是用来代替 老的DES的。

AES加密算法的加密块必须是16字节(128bit)，所以不足部分需要填充，常用的填充算法是PKCS7。

AES加密算法的key可以是16字节(AES128)，或者24字节(AES192)，或者是32字节(AES256)

2. AES算法的具体实现种类

ECB：Electronic Codebook Book

CBC：Cipher Block Chaining：这是最常见的块加密实现

CTR：Counter

CFB：Cipher FeedBack

OFB：Output FeedBack

具体的差异我也没去弄明白，知道这么个意思，加密算法稍后差异。

3. golang crypt库实现的加密函数

包括AES，CBC，CTR，OFB，CFB，GCM。

这其中GCM不需要加密块必须16字节长度，可以是任意长度，其他的都需要16字节对其，所以不足部分都需要补充。

package main

import (
   "io"
   "fmt"
   "crypto/aes"
   "crypto/cipher"
   "crypto/rand"
)

func main() {
  key := []byte("12345678901234567890123456789012")    // 32 bytes long

  plainText := []byte("123")
  fmt.Printf("Original  Text: [%s]\n",plainText)

  cipherText, _  := AESEncrypt(key, plainText)   // replace with corresponding encrypt implementation
  decryptText, _ := AESDecrypt(key, cipherText)
  fmt.Printf("AES Decrypted Text: [%s]\n", decryptText)
}

3.1 AES

func AESEncrypt(key []byte, data[]byte) ([]byte, error) {
    data = pad(data, aes.BlockSize)
    c, _ := aes.NewCipher(key)
    out := make([]byte, len(data))
    c.Encrypt(out, []byte(data))
    return out, nil
}

func AESDecrypt(key []byte, data[]byte) ([]byte, error) {
    c, _ := aes.NewCipher(key)
    out := make([]byte, len(data))
    c.Decrypt(out, data)

    out, _ = unpad(out)
    return out, nil
}

3.2 CBC

func CBCEncrypt(key []byte, data []byte) ([]byte, error) {
    data = pad(data, aes.BlockSize)
    block, _ := aes.NewCipher(key)
    out := make([]byte, aes.BlockSize + len(data))
    iv := out[:aes.BlockSize]
    io.ReadFull(rand.Reader, iv)

    mode := cipher.NewCBCEncrypter(block, iv)
    mode.CryptBlocks(out[aes.BlockSize:], []byte(data))
    return out, nil
}

func CBCDecrypt(key []byte, data []byte) ([]byte, error) {
    block, _ := aes.NewCipher(key)
    iv  := data[:aes.BlockSize]
    data = data[aes.BlockSize:]
    if len(data) % aes.BlockSize != 0 {
      return nil, fmt.Errorf("data is not a multiple of the block size")
    }

    out := make([]byte, len(data))
    mode := cipher.NewCBCDecrypter(block, iv)
    mode.CryptBlocks(out, data)

    out, _ = unpad(out)
    return out, nil
}

3.3 CTR

func CTREncrypt(key []byte, data[]byte) ([]byte, error) {
    data = pad(data, aes.BlockSize)
    block, _ := aes.NewCipher([]byte(key))
    out := make([]byte, aes.BlockSize + len(data))
    iv := out[:aes.BlockSize]
    if _, err := io.ReadFull(rand.Reader, iv); err != nil {
        return nil, err
    }

    stream := cipher.NewCTR(block, iv)
    stream.XORKeyStream(out[aes.BlockSize:], data)
    return out, nil
}

func CTRDecrypt(key []byte, data[]byte) ([]byte, error) {
    block, _ := aes.NewCipher([]byte(key))
    iv  := data[:aes.BlockSize]
    data = data[aes.BlockSize:]
    if len(data) % aes.BlockSize != 0 {
        return nil, fmt.Errorf("data is not a multiple of the block size")
    }

    out := make([]byte, len(data))
    mode := cipher.NewCTR(block, iv)
    mode.XORKeyStream(out, data)

    out, _ = unpad(out)
    return out, nil
}

3.4 OFB

func OFBEncrypt(key []byte, data[]byte) ([]byte, error) {
    data = pad(data, aes.BlockSize)
    block, _ := aes.NewCipher([]byte(key))
    out := make([]byte, aes.BlockSize + len(data))
    iv := out[:aes.BlockSize]
    if _, err := io.ReadFull(rand.Reader, iv); err != nil {
        return nil, err
    }

    stream := cipher.NewOFB(block, iv)
    stream.XORKeyStream(out[aes.BlockSize:], data)
    return out, nil
}

func OFBDecrypt(key []byte, data[]byte) ([]byte, error) {
    block, _ := aes.NewCipher([]byte(key))
    iv  := data[:aes.BlockSize]
    data = data[aes.BlockSize:]
    if len(data) % aes.BlockSize != 0 {
        return nil, fmt.Errorf("data is not a multiple of the block size")
    }

    out := make([]byte, len(data))
    mode := cipher.NewOFB(block, iv)
    mode.XORKeyStream(out, data)

    out, _ = unpad(out)
    return out, nil
}

3.5 CFB

func CFBEncrypt(key []byte, data[]byte) ([]byte, error) {
    data = pad(data, aes.BlockSize)
    block, _ := aes.NewCipher([]byte(key))

    out := make([]byte, aes.BlockSize + len(data))
    iv := out[:aes.BlockSize]
    if _, err := io.ReadFull(rand.Reader, iv); err != nil {
        return nil, err
    }

    stream := cipher.NewCFBEncrypter(block, iv)
    stream.XORKeyStream(out[aes.BlockSize:], data)
    return out, nil
}

func CFBDecrypt(key []byte, data[]byte) ([]byte, error) {
    block, _ := aes.NewCipher([]byte(key))
    iv  := data[:aes.BlockSize]
    data = data[aes.BlockSize:]
    if len(data) % aes.BlockSize != 0 {
        return nil, fmt.Errorf("data is not a multiple of the block size")
    }

    out := make([]byte, len(data))
    mode := cipher.NewCFBDecrypter(block, iv)
    mode.XORKeyStream(out, data)

    out, _ = unpad(out)
    return out, nil
}

3.6 GCM

GCM实现算法不需要pad。

func GCMEncrypt(key []byte, data[]byte) ([]byte, error) {
    block, _ := aes.NewCipher([]byte(key))
    aesgcm, _ := cipher.NewGCM(block)

    nonce := make([]byte, aesgcm.NonceSize())
    io.ReadFull(rand.Reader, nonce)

    out := aesgcm.Seal(nonce, nonce, data, nil)
    return out, nil
}

func GCMDecrypt(key []byte, data[]byte) ([]byte, error) {
    block, _ := aes.NewCipher([]byte(key))
    aesgcm, _ := cipher.NewGCM(block)

    nonce, ciphertext := data[:aesgcm.NonceSize()], data[aesgcm.NonceSize():]
    out, err := aesgcm.Open(nil, nonce, ciphertext, nil)

    return out, nil
}