Java：AES/CFB/nopadding加密与Base64编码

Question

我想在Java中使用aes/cfb/nopadding加密字节。

package main

import (
    "io"
    "crypto/aes"
    "crypto/cipher"
    "encoding/base64"
    "crypto/rand"
)

func encrypt(key, data []byte) string {
    block, err := aes.NewCipher(key)
    if err != nil {
      return nil, err
    }
    encoded := base64.StdEncoding.EncodeToString(data)
    ciphertext := make( []byte, aes.BlockSize+len(encoded) )
    iv := ciphertext[:aes.BlockSize]
    if _, err := io.ReadFull(rand.Reader, iv); err != nil {
      return nil, err
    }
    cfb := cipher.NewCFBEncrypter(block, iv)
    cfb.XORKeyStream( ciphertext[aes.BlockSize:], []byte(encoded) )
    return ciphertext, nil
}

func decrypt(key, data []byte) ([]byte, error) {
  blockcipher, err := aes.NewCipher(key)
  if err != nil {
    return nil, err
  }
  if len(data) < aes.BlockSize {
    return nil, errors.New("ciphertext too short")
  }
  iv := data[:aes.BlockSize]
  data = data[aes.BlockSize:]
  cfb := cipher.NewCFBDecrypter(blockcipher, iv)
  cfb.XORKeyStream(data, data)
  return data, nil
}

private byte[] encrypt(byte[] payload) {
    try {
        SecretKeySpec key_spec = new SecretKeySpec(current_encryption_key, "AES");
        Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
        byte[] encoded_payload = Base64.encode(payload, Base64.DEFAULT);
        IvParameterSpec iv = new IvParameterSpec( new byte[16] );
        cipher.init(Cipher.ENCRYPT_MODE, key_spec, iv);
        return cipher.doFinal(encoded_payload);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return new byte[0];
}

我的加密代码如下所示（在Golang和Java中都能正常工作）：

private byte[] decrypt(byte[] payload) {
    try {
        SecretKeySpec key_spec = new SecretKeySpec(current_encryption_key, "AES");
        Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
        int block_size = cipher.getBlockSize();
        IvParameterSpec iv = new IvParameterSpec( Arrays.copyOf(payload, block_size) );
        byte[] decryption_data = Arrays.copyOfRange(payload, block_size, payload.length);
        cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);
        byte[] decrypted_payload = cipher.doFinal(decryption_data);
        return Base64.decode(decrypted_payload, Base64.DEFAULT);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return new byte[0];
}

当我在Java中加密某些内容，然后尝试使用Java中的解密器时，我得到以下解密错误：

04-13 14:16:48.382 3791-3791/com.domain.interpretest W/System.err: java.lang.IllegalArgumentException: 16 > 9
04-13 14:16:48.388 3791-3791/com.domain.interpretest W/System.err:     at java.util.Arrays.copyOfRange(Arrays.java:3447)

Answer 1

Go加密摘要：

• 用一个随机的IV（和您没有描述的密钥）加密base-64ed数据，将IV和密文放在一个缓冲区中

您的Java解密摘要：

null

null

解决方案：您的Java加密应该使用一个随机的IV，并返回一个缓冲区，其中包含IV后跟密文，就像Go加密一样。一种非常类似于你的方法：

// once, during initialization 
SecureRandom rand = new SecureRandom(); // or .getInstance* as you prefer 

// unchanged 
SecretKeySpec key_spec = new SecretKeySpec(current_encryption_key, "AES");
Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
byte[] encoded_payload = Base64.encode(payload, Base64.DEFAULT);
// changed 
int block_size = cipher.getBlockSize();
// create random IV
byte[] buffer = new byte[block_size];
rand.nextBytes(buffer);
IvParameterSpec iv = new IvParameterSpec (buffer);
// expand buffer already containing IV to make room for ciphertext
buffer = Arrays.copyOf (buffer, block_size+encoded_payload.length);
// unchanged 
cipher.init(Cipher.ENCRYPT_MODE, key_spec, iv);
// changed
// do encryption into correct part of existing buffer
cipher.doFinal(encoded_payload,0,encoded_payload.length, buffer,block_size);
return buffer;

PS：你为什么要费心用base64编码和解码明文呢？像所有现代密码一样，AES可以很好地处理任何比特的组合。当其他代码不能将密文和IV作为位/二进制来处理时，使用base64更常见。