Best way to use PHP to encrypt and decrypt passwords? [duplicate]

Possible Duplicate:
PHP 2-way encryption: I need to store passwords that can be retrieved

I plan to store foreign account information for my users on my website, aka rapidshare username and passwords, etc... I want to keep information secure, but I know that if I hash their information, I can't retrieve it for later use.

Base64 is decrypt-able so there's no point using that just plain off. My idea is to scramble the user and pass before and after it gets base64ed that way even after you decrypt it, you get some funny looking text if you try to decrypt. Is there a php function that accepts values that will make an unique scramble of a string and de-scramble it later when the value is reinputed?

Any suggestions?

You should not encrypt passwords, instead you should hash them using an algorithm like bcrypt. This answer explains how to properly implement password hashing in PHP. Still, here is how you would encrypt/decrypt:

$key = 'password to (en/de)crypt';
$string = ' string to be encrypted '; // note the spaces

To Encrypt:

$iv = mcrypt_create_iv(
    mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC),
    MCRYPT_DEV_URANDOM
);

$encrypted = base64_encode(
    $iv .
    mcrypt_encrypt(
        MCRYPT_RIJNDAEL_128,
        hash('sha256', $key, true),
        $string,
        MCRYPT_MODE_CBC,
        $iv
    )
);

To Decrypt:

$data = base64_decode($encrypted);
$iv = substr($data, 0, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC));

$decrypted = rtrim(
    mcrypt_decrypt(
        MCRYPT_RIJNDAEL_128,
        hash('sha256', $key, true),
        substr($data, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC)),
        MCRYPT_MODE_CBC,
        $iv
    ),
    "\0"
);

Warning: The above example encrypts information, but it does not authenticate the ciphertext to prevent tampering. You should not rely on unauthenticated encryption for security, especially since the code as provided is vulnerable to padding oracle attacks.

See also:

• https://stackoverflow.com/a/30189841/2224584
• https://stackoverflow.com/a/30166085/2224584
• https://stackoverflow.com/a/30159120/2224584

Also, don't just use a "password" for an encryption key. Encryption keys are random strings.

Demo at 3v4l.org:

echo 'Encrypted:' . "\n";
var_dump($encrypted); // "m1DSXVlAKJnLm7k3WrVd51omGL/05JJrPluBonO9W+9ohkNuw8rWdJW6NeLNc688="

echo "\n";

echo 'Decrypted:' . "\n";
var_dump($decrypted); // " string to be encrypted "

Security Warning: This class is not secure. It's using Rijndael256-ECB, which is not semantically secure. Just because "it works" doesn't mean "it's secure". Also, it strips tailing spaces afterwards due to not using proper padding.

Found this class recently, it works like a dream!

class Encryption {
    var $skey = "yourSecretKey"; // you can change it

    public  function safe_b64encode($string) {
        $data = base64_encode($string);
        $data = str_replace(array('+','/','='),array('-','_',''),$data);
        return $data;
    }

    public function safe_b64decode($string) {
        $data = str_replace(array('-','_'),array('+','/'),$string);
        $mod4 = strlen($data) % 4;
        if ($mod4) {
            $data .= substr('====', $mod4);
        }
        return base64_decode($data);
    }

    public  function encode($value){ 
        if(!$value){return false;}
        $text = $value;
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $this->skey, $text, MCRYPT_MODE_ECB, $iv);
        return trim($this->safe_b64encode($crypttext)); 
    }

    public function decode($value){
        if(!$value){return false;}
        $crypttext = $this->safe_b64decode($value); 
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        $decrypttext = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $this->skey, $crypttext, MCRYPT_MODE_ECB, $iv);
        return trim($decrypttext);
    }
}

And to call it:

$str = "My secret String";

$converter = new Encryption;
$encoded = $converter->encode($str );
$decoded = $converter->decode($encoded);    

echo "$encoded<p>$decoded";