Android AES解密和来自iOS的数据：javax.crypto.BadPaddingException：pad块损坏

Question

public  String decrypt(byte[] cipherText, SecretKey key, byte [] initialVector) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
    IvParameterSpec ivParameterSpec = new IvParameterSpec(initialVector);
    cipher.init(Cipher.DECRYPT_MODE, key, ivParameterSpec);
    cipherText = cipher.doFinal(cipherText);

    return new String(cipherText, "UTF-8");
}

public static byte[] decodeWebSafe(String s) throws Base64DecoderException {
    byte[] bytes = s.getBytes();
    return decodeWebSafe(bytes, 0, bytes.length);
}

byte[] iv = Base64.decodeWebSafe(enciv);
byte[] salt = Base64.decodeWebSafe(encsalt);
byte[] data = Base64.decodeWebSafe(encdata);
SecretKey key = Security.getExistingKey(password, salt);
String original = aes.decrypt(data, key, iv);

public static SecretKey getExistingKey(String password, byte[] salt) throws Exception{
    SecretKey key= null;
    KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, 10000, 256);
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");

    byte[] keyBytes=new byte[32]; 
    keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
    key= new SecretKeySpec(keyBytes, "AES");

    return key;
}

附注：这是我们在IOS中设置加密的方式：

CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
self.encryptionKey.bytes, kCCKeySizeAES128,
self.encryptionIV.bytes, [rawData bytes], dataLength, 
/* input */buffer, bufferSize, /* output */&numBytesEncrypted);

key和IV的推导方法：

(NSData *)keyForPassword:(NSString *)password salt:(NSData *)salt {
NSMutableData *
derivedKey = [NSMutableData dataWithLength:kCCKeySizeAES128];

int result = CCKeyDerivationPBKDF(kCCPBKDF2,            // algorithm
                              password.UTF8String, 
                              password.length,  
                              salt.bytes,           // salt
                              salt.length,          // saltLen
                              kCCPRFHmacAlgSHA1,    // PRF
                              kPBKDFRounds,         // rounds
                              derivedKey.mutableBytes, // derivedKey
                              derivedKey.length); // derivedKeyLen
}

Answer 1

我可以看到您生成密钥的方式有几个不同之处：

• 在iOS中，生成16字节/128位的密钥；在Android中是256位。
• 在iOS中，密码是UTF-8编码的，而Android要么取每个字符的低8位，要么取完整的16位（具体算法细节我不知道）。
• 在iOS中，您传递的密码长度无效（在UTF-8编码中是字符数，而不是字节数）。

您最好在更好地匹配密钥生成和解密前比较密钥方面投入一些时间。