加密/解密会导致字符串开头的替换和不正确的字符

Question

Here are my encrypt and decrypt functions

public function encrypt($text){
        $key = hash("md5", KEY);
        $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_TWOFISH, MCRYPT_MODE_CBC), MCRYPT_RAND);
        $result = base64_encode(mcrypt_encrypt(MCRYPT_TWOFISH, $key, $text, MCRYPT_MODE_CBC, $iv));
        return $result;
}

public function decrypt($text){
        $key = hash("md5", KEY);
        $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_TWOFISH, MCRYPT_MODE_CBC), MCRYPT_RAND);
        $result = trim(mcrypt_decrypt(MCRYPT_TWOFISH, $key, base64_decode($text), MCRYPT_MODE_CBC, $iv));    
        return $result;
}

When encryption is run on a JSON string to be stored as a text file and then retrieved and decrypted the front section of the resulting string has replacement and/or incorrect characters:

Expected:

{"players":[{"label":"...

Actual:

�Ӹ�!G@${�W�Rՙ�bel":"...

If it makes any difference the actual placement/incorrect chars are different each time I refresh the page on the same file.

Answer 1

In case anyone comes across this...

The IV needs to be prepended to the file before encoding, like so:

public function encrypt($text){
    $key = hash("md5", KEY);
    $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_TWOFISH, MCRYPT_MODE_CBC), MCRYPT_DEV_URANDOM);
    $result = base64_encode($iv.mcrypt_encrypt(MCRYPT_TWOFISH, $key, $text, MCRYPT_MODE_CBC, $iv));
    return $result;
}

Then when decrypting take the IV from the decoded string and use it to decrypt, like so:

public function decrypt($text){
    $key = hash("md5", KEY);
    $decode = base64_decode($text);
    $iv = substr($decode, 0, 16);
    $decrypt = substr($decode, 16);
    $result = mcrypt_decrypt(MCRYPT_TWOFISH, $key, $decrypt, MCRYPT_MODE_CBC, $iv);
    return $result;
}