php objective-c 中的 AES256 加密兼容性

Question

我在 php 中编写了一个代码（作为一项服务）来解密通过协议发送的密码。该协议要求使用 AES256 "Mac then Encrypt"ed (MtE) 密码，然后使用 base-64 编码。

base46encoded (iv + ecrypted(mac + password))

使用 php

过程很简单

public static function getPassword($password, $key, $mac_algorithm = 'sha1',
                                       $enc_algorithm = MCRYPT_RIJNDAEL_256, $enc_mode = MCRYPT_MODE_CBC)
    {
        // truncating pre-shared key to 32 bytes.
        $key = substr($key, 0, 32);

        // decoding the message (being a password) from base64
        $password = base64_decode($password);

        // getting the iv size based on algorithm and encryption mode
        $iv_size = mcrypt_get_iv_size($enc_algorithm, $enc_mode);

        // extracting iv from message header (normally the first 32 byte) for decryption
        $iv_dec = substr($password, 0, $iv_size);

        // getting the encrypted message after the header (after the first 32 byte)
        $password = substr($password, $iv_size);

        // decrypting message using the pre-shared key and extracted iv
        $password = mcrypt_decrypt($enc_algorithm, $key, $password, $enc_mode, $iv_dec);

        // getting block size for hash algorithm in bytes (sha1 block size is 160 bit)
        $mac_block_size = ceil(static::getMacAlgoBlockSize($mac_algorithm)/8);

        // extracting the mac from the header of decrypted message
        $mac_dec = substr($password, 0, $mac_block_size);

        // extracting the valuable message
        $password = substr($password, $mac_block_size);

        // eliminate extra null terminators padded as the result of enc/decryption the following if and the next statement are check clauses for unpack function
        $password = unpack('Z*', $password);
        if (!isset($password[1]))
        {
            return false;
        }

        // obtaining the pure intended message (being the password) from the unpack result
        $password = $password[1];

        // regenerating the mac to control the authenticity and correctness of transmission
        $mac = hash_hmac($mac_algorithm, $password, $key, true);

        // see if transmitted mac (mac_dec) and the generated mac are the same and the data is valid
        if($mac_dec == $mac)
        {
            return $password;
        }
        else
        {
            return false;
        }
    }

现在的问题是，iOS就是围绕这个协议开发的应用，试过AESCrypt和CCCrypt，但是解密结果不一样（乱码）

我们使用标准 CCHmac，Base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithCarriageReturn 和 This SO answer 用于 CCCrypt。

Answer 1

mcrypt_generic_init 函数通过指定密钥和 IV 来初始化密码。密钥的长度决定了我们进行的是 128 位、192 位还是 256 位加密。

所以使用 MCRYPT_RIJNDAEL_128 与 256 位（32 字节）密钥兼容 AES256。

php objective-c 中的 AES256 加密兼容性

php AES256 encryption compatibility in objective-c

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