AES/ECB/PKCS5Padding加密：Java与Python结果不一致求助

问题说明 #

参照Java的AES加密逻辑编写Python版本代码，但两者输出的加密结果完全不同，排查多日未解决，需技术协助。

Java原加密代码 #

public String encrypt(String strToEncrypt, String myKey) throws Exception {
    try {
        MessageDigest sha = null;
        byte[] key = myKey.getBytes("UTF-8");
        sha = MessageDigest.getInstance("SHA-1");
        key = sha.digest(key);
        key = Arrays.copyOf(key, 32); // 将SHA-1的20字节结果补0到32字节
        SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        return Base64.getEncoder().encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")));
    } catch (Exception e) {
        throw e;
    }
}

原Python实现代码 #

import base64
import hashlib
from Crypto.Cipher import AES

def encrypt(str_to_encrypt, my_key):
    try:
        sha = hashlib.sha1()
        sha.update(my_key.encode('utf-8'))
        key = sha.digest()
        key = key[:16]  # 错误：仅取前16字节，对应AES-128，与Java逻辑不符
        cipher = AES.new(key, AES.MODE_ECB)
        byte_array = str_to_encrypt.encode("UTF-8")
        padded_data = pad(byte_array, AES.block_size)
        encrypted_data = cipher.encrypt(padded_data)
        return base64.b64encode(encrypted_data).decode('utf-8')
    except Exception as e:
        raise e

def pad(byte_array: bytearray, block_size: int):
    pad_len = block_size - len(byte_array) % block_size
    return byte_array + (bytes([pad_len]) * pad_len)

# 测试示例
my_key = "mySecretKey"
str_to_encrypt = "This is the string to encrypt"
encrypted_string = encrypt(str_to_encrypt, my_key)
print(encrypted_string)

结果对比 #

• Java加密结果：0xfLbMxzLp0B1v10jgySMuPsNn74Ow55x2R6GUyY9XE=
• 原Python加密结果：jhfQIBB0vFeerfp1LdhZwIW/Bj6VXsPy84YWkci8oPA=

问题核心原因 #

1. 密钥长度不匹配：Java代码中，SHA-1生成20字节密钥后，通过Arrays.copyOf(key, 32)将密钥补0填充至32字节，使用AES-256加密；而原Python代码仅取前16字节，使用AES-128加密，这是结果不一致的根本原因。
2. 填充逻辑两者一致（均为PKCS5Padding），此部分无问题。

修正后的Python代码 #

import base64
import hashlib
from Crypto.Cipher import AES

def encrypt(str_to_encrypt, my_key):
    try:
        sha = hashlib.sha1()
        sha.update(my_key.encode('utf-8'))
        key = sha.digest()
        # 对应Java的Arrays.copyOf(key, 32)：将20字节SHA-1结果补0至32字节
        key = key.ljust(32, b'\x00')
        cipher = AES.new(key, AES.MODE_ECB)
        byte_array = str_to_encrypt.encode("UTF-8")
        padded_data = pad(byte_array, AES.block_size)
        encrypted_data = cipher.encrypt(padded_data)
        return base64.b64encode(encrypted_data).decode('utf-8')
    except Exception as e:
        raise e

def pad(byte_array: bytes, block_size: int):
    pad_len = block_size - len(byte_array) % block_size
    return byte_array + (bytes([pad_len]) * pad_len)

# 测试示例
my_key = "mySecretKey"
str_to_encrypt = "This is the string to encrypt"
encrypted_string = encrypt(str_to_encrypt, my_key)
print(encrypted_string)  # 输出与Java一致：0xfLbMxzLp0B1v10jgySMuPsNn74Ow55x2R6GUyY9XE=

内容的提问来源于stack exchange，提问作者Shubham