<?php
function encrypt($decrypted, $password, $salt='!kQm*fF3pXe1Kbm%9') {
	// Build a 256-bit $key which is a SHA256 hash of $salt and $password.
	$key = hash('SHA256', $salt . $password, true);
	// Build $iv and $iv_base64.  We use a block size of 128 bits (AES compliant) and CBC mode.  (Note: ECB mode is inadequate as IV is not used.)
	srand(); $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_RAND);
	if (strlen($iv_base64 = rtrim(base64_encode($iv), '=')) != 22) return false;
	// Encrypt $decrypted and an MD5 of $decrypted using $key.  MD5 is fine to use here because it's just to verify successful decryption.
	$encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $decrypted . md5($decrypted), MCRYPT_MODE_CBC, $iv));
	// We're done!
	return $iv_base64 . $encrypted;
}

function decrypt($encrypted, $password, $salt='!kQm*fF3pXe1Kbm%9') {
	// Build a 256-bit $key which is a SHA256 hash of $salt and $password.
	$key = hash('SHA256', $salt . $password, true);
	// Retrieve $iv which is the first 22 characters plus ==, base64_decoded.
	$iv = base64_decode(substr($encrypted, 0, 22) . '==');
	// Remove $iv from $encrypted.
	$encrypted = substr($encrypted, 22);
	// Decrypt the data.  rtrim won't corrupt the data because the last 32 characters are the md5 hash; thus any \0 character has to be padding.
	$decrypted = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, base64_decode($encrypted), MCRYPT_MODE_CBC, $iv), "\0\4");
	// Retrieve $hash which is the last 32 characters of $decrypted.
	$hash = substr($decrypted, -32);
	// Remove the last 32 characters from $decrypted.
	$decrypted = substr($decrypted, 0, -32);
	// Integrity check.  If this fails, either the data is corrupted, or the password/salt was incorrect.
	if (md5($decrypted) != $hash) return false;
	// Yay!
	return $decrypted;
}

//Dont change the salt, the salt will be same

// lets say you let your user sign up, he will enter password = "mybroeddie", and year of birth = "1991"

//when he submits the form, you get those values in your php and then do this

$password = sha1(md5("mybroeddie")); //assume we have someting like this
$year = "1991";

	//NOW,

$userskey = base64_encode($password . $year);

//so now you have the users key.
// lets say you want to encrypt their firstname

$firstname = "Eddie Brewer";

$value_in_db =  encrypt($firstname, $userskey); //HtPigqENKqg/aLtv5vIB0gsuFKHr8yS12hDK+SWWEFWUhCnKK+aznYrLxTU8cRF2DZpkCdGXVF9hWXX6J3ZuSG <-- Save this to your database

//so now when ever user wants to see their data, you give them 2 text boxes and ask them to enter their password and year of birth.

//CASE 1 : They enter wrongly

$inputpasswordbyuser = "mypass";

// then you would do the exact same stuff which you did before

$password = sha1(md5($inputpasswordbyuser));
$year = "1991"; //assuming he gets the year right somehow


$userskey = base64_encode($password . $year); //so now your system made the key with the wrongly provided stuff, lets see if this can decrypt your data;

$yourdatafromdb = "HtPigqENKqg/aLtv5vIB0gsuFKHr8yS12hDK+SWWEFWUhCnKK+aznYrLxTU8cRF2DZpkCdGXVF9hWXX6J3ZuSG";

//echo decrypt($yourdatafromdb, $userskey);



//CASE 2 : They enter CORRECTLY

$inputpasswordbyuser = "mybroeddie";

// then you would do the exact same stuff which you did before

$password = sha1(md5($inputpasswordbyuser));
$year = "1991"; //assuming he gets the year right somehow


$userskey = base64_encode($password . $year); //so now your system made the key with the wrongly provided stuff, lets see if this can decrypt your data;

$yourdatafromdb = "HtPigqENKqg/aLtv5vIB0gsuFKHr8yS12hDK+SWWEFWUhCnKK+aznYrLxTU8cRF2DZpkCdGXVF9hWXX6J3ZuSG";

echo decrypt($yourdatafromdb, $userskey);









//$res = encrypt("myssn123", "mysecretkey");
//echo "ENCRYTPTED STUFF IS : " . $res;

//echo "<br/><br/>DECRYPTED STUFF IS : " . decrypt($res, "mysecretkey");


?>