mcrypt_decrypt return strange code - php

Question

I tried to encrypt an array then decrypt it back to string by calling a function, it's seem return the correct value if I does all encrypt and decrypt at once time in the function, however, if I return the encrypt value, then call the function again to decrypt it will return me some strange code.
Example 1:
public main()
{
$dataArray = array("one"=>1, "two"=>2, "three"=>3);
$a = $this->encryptDecryptInfo(json_encode($dataArray),$this->key);
var_dump($a);
}
public function encryptDecryptInfo($text,$key)
{
$iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256,
$text= base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_CFB, $iv));
return mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, base64_decode($text), MCRYPT_MODE_CFB, $iv);
}
This will return me the correct value which is string(27) "{"one":1,"two":2,"three":3}"
Example 2:
public main()
{
$dataArray = array("one"=>1, "two"=>2, "three"=>3);
$a = $this->encryptDecryptInfo(json_encode($dataArray),$this->key,"encrypt");
$b = $this->encryptDecryptInfo($a,$this->key,"decrypt");
var_dump($b);
}
public function encryptDecryptInfo($text,$key,$type)
{
$iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CFB), MCRYPT_RAND);
if($type == "encrypt")
return base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_CFB, $iv));
else return mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, base64_decode($text), MCRYPT_MODE_CFB, $iv);
}
However if I do my code in this way, it will return me strange value which is like this string(27) "�ÔérôŸY éXgíœÈÐN*é౜CµÖ" .
Deos anyone know why this is happen? Both encrypt and decrypt coding are the same for example 1 and example 2, but why it will return strange code in example instead? Any way to fix this issue?

Answer 1

I think this is encoding issue look for UTF here - http://php.net/manual/en/function.base64-encode.php in the comments there is a UTF8 safe encoding function.
By passing the parameters left and right you are changing the encoding and you loose it in the translation. Welcome to PHP :)

Answer 2

You must use the same IV for decryption. Just save it along with encrypted data, for example:
if($type == "encrypt") {
$iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CFB), MCRYPT_RAND);
return base64_encode($iv . '##' .
mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_CFB, $iv));
} else {
list($iv, $data) = explode('##', base64_decode($text));
return mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $data, MCRYPT_MODE_CFB, $iv);
}

Answer 3

I had a similar issue. In the database I originally set it up for 16 characters. When I changed to encrypting, I forgot to change that number so the entire encrypted value was not stored. Once I corrected this it returned normal characters :)