Java - Python AES 加密解密

Question

我有一个使用 AES 来自 Java(v8) 的加密文本，我试图在 python 中使用相同的 SecretKey、Salt 对其进行解密，但是在取消索引超出范围时遇到问题。当我做相反的事情时，即在 python 中加密并在 java 中解密然后我能够得到文本，但带有一些不需要的前缀。

以下是我尝试过的java和python代码。

Java 代码（来自 org.apache.commons.codec.binary.Base64 的 Base64）

public static String encrypt(String secretKey, String salt, String value) throws Exception {
        Cipher cipher = initCipher(secretKey, salt, Cipher.ENCRYPT_MODE);
        byte[] encrypted = cipher.doFinal(value.getBytes());
        return Base64.encodeBase64String(encrypted);
    }

    public static String decrypt(String secretKey, String salt, String encrypted) throws Exception {
        Cipher cipher = initCipher(secretKey, salt, Cipher.DECRYPT_MODE);
        byte[] original = cipher.doFinal(Base64.decodeBase64(encrypted));
        return new String(original);
    }

    private static Cipher initCipher(String secretKey, String salt, int mode) throws Exception {

        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");

        KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt.getBytes(), 65536, 256);
        SecretKey tmp = factory.generateSecret(spec);
        SecretKeySpec skeySpec = new SecretKeySpec(tmp.getEncoded(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
        cipher.init(mode, skeySpec, new IvParameterSpec(new byte[16]));
        return cipher;
    }

    public static void main(String[] args) throws Exception {
        String secretKey = "Secret";
        String fSalt = "tJHnN5b1i6wvXMwzYMRk";
        String plainText = "England";

        String cipherText = encrypt(secretKey, fSalt, plainText);
        System.out.println("Cipher: " + cipherText);
//      cipherText = "6peDTxE1xgLE4hTGg0PKTnuuhFC1Vftsd7NH9DF/7WM="; // Cipher from python
        String dcrCipherText = decrypt(secretKey, fSalt, cipherText);
        System.out.println(dcrCipherText);

    }

Python 代码（3.6 版）和 Pycrypto V2.6

import base64
import hashlib
import os

from Crypto.Cipher import AES

BS = 16
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)

# unpad = lambda s: s[:-ord(s[len(s) - 1:])]
unpad = lambda s: s[0:-s[-1]]

def get_private_key(secretKey, salt):
    key = hashlib.pbkdf2_hmac('SHA256', secretKey.encode(), salt.encode(), 65536, 32)
    return key


def encrypt(message, salt, secretKey):
    private_key = get_private_key(secretKey, salt)
    message = pad(message)
    iv = os.urandom(BS)  # 128-bit IV
    cipher = AES.new(private_key, AES.MODE_CBC, iv, segment_size=256)
    return base64.b64encode(iv + cipher.encrypt(message))


def decrypt(enc, salt, secretKey):
    private_key = get_private_key(secretKey, salt)
    enc = base64.b64decode(enc)
    iv = enc[:BS]
    cipher = AES.new(private_key, AES.MODE_CBC, iv, segment_size=256)
    return unpad(cipher.decrypt(enc[BS:]))


secretKey = "Secret"
salt = "tJHnN5b1i6wvXMwzYMRk"
plainText = "England"
cipher = encrypt(plainText, salt, secretKey)
print("Cipher: " + bytes.decode(cipher))

# cipher = "0JrZdg9YBRshfTdr1d4zwQ==" # Cipher from java
decrypted = decrypt(cipher, salt, secretKey)
print("Decrypted " + bytes.decode(decrypted))

Java 解密输出：�U�����or���England 当我通过 python 密码时，预期：England Python 解密输出：unpad = lambda s : s[0:-s[-1]] IndexError: index out of range，预期：England

关于这个问题，我也浏览了堆栈上的其他帖子，但是由于他们使用了不同的模式，所以没有成功。

Answer 1

使用pycryptodome 的正确python 3 代码将与Java 代码匹配，如下所示：

import base64
from Crypto.Cipher import AES
from Crypto.Util.Padding import unpad,pad
import hashlib

def get_private_key(secretKey, salt):
    # _prf = lambda p,s: HMAC.new(p, s, SHA256).digest()
    # private_key = PBKDF2(secretKey, salt.encode(), dkLen=32,count=65536, prf=_prf )
    # above code is equivalent but slow
    key = hashlib.pbkdf2_hmac('SHA256', secretKey.encode(), salt.encode(), 65536, 32)
    # KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt.getBytes(), 65536, 256);
    return key

def encrypt(message, salt, secretKey):
    private_key = get_private_key(secretKey, salt)
    message = pad(message.encode(), AES.block_size)
    iv = "\x00"*AES.block_size  # 128-bit IV
    cipher = AES.new(private_key, AES.MODE_CBC, iv.encode())
    return base64.b64encode(cipher.encrypt(message))


def decrypt(enc, salt, secretKey):
    # _prf = lambda p,s: HMAC.new(p, s, SHA256).digest()
    # private_key = PBKDF2(secretKey, salt.encode(), dkLen=32,count=65536, prf=_prf )
    private_key = get_private_key(secretKey, salt)
    enc = base64.b64decode(enc)
    iv = "\x00"*AES.block_size
    cipher = AES.new(private_key, AES.MODE_CBC, iv.encode())
    return unpad(cipher.decrypt(enc), AES.block_size).decode('utf-8')


secretKey = "Secret"
salt = "tJHnN5b1i6wvXMwzYMRk"
plainText = "England"
enc_datta = encrypt(plainText, salt, secretKey)
print(f"Encrypted: {enc_datta}")
# Encrypted: 0JrZdg9YBRshfTdr1d4zwQ==

cipher = "0JrZdg9YBRshfTdr1d4zwQ==" # Cipher from java
decrypted = decrypt(cipher, salt, secretKey)
print(f"Decrypted: {decrypted}" )
# Decrypted: England

Answer 2

在 python 中，您将 iv（初始化向量）存储在加密消息的前 16 个字节中。

在 Java 中，您并没有做这样的事情 - 您传递的是一个空的 IV，并且您将包括前 16 个字节在内的整个消息视为密文。

您需要确保 Java 和 Python 匹配。

您要么在两者中都不使用 IV，在这种情况下，您将在 Python 中删除该部分。

或者您在两者中都使用 IV，在这种情况下，您需要更新 Java 代码以在加密时生成随机 IV，并将其添加到加密结果中。解密时，Java 代码需要将前 16 个字节作为 IV 并传递给Cipher。