base64_hash.php

<?php

/*
 * Because we are removing the ending `=` padding we will have a string length of
 * md5 <= 24
 * sha1 <= 28
 *
 * Probably should just remove the code that trims the equal sign since it's kind of pointless....
 */

$value = microtime(TRUE);

function base64_hash($data, $algo = 'md5')
{
	// also remove the extra `=` trailing padding.
	return rtrim(base64_encode(pack('H*', $algo($data))), '=');
}

function base64_hash_restore($hash)
{
	// If the length isn't a multiple of 4 characters, add = characters until it is
	$number = abs(4 - (strlen($hash) % 4));
	return $hash . str_repeat('=', $number === 4 ? 0 : $number);
}

$hash = base64_hash($value);

foreach (array('md5', 'sha1') as $algo) {
	print $algo . "\n";
	for ($i=0; $i < 5; $i++) {
		print $hash . ' + ' . $i . ' = ' . (strlen($hash) + $i) . "\n";
		$new = base64_hash_restore($hash . str_repeat('=', $i), $algo);
		print $new . ' : ' . strlen($new). "\n";
	}
}