MD5-based block cipher
Below is a MD5-based block cipher (MDC-like), which works in 128bit CFB mode.
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It is very useful to encrypt secret data before transfer it over the network.
function md5_encrypt($plain_text, $password, $iv_len = 16){
$plain_text .= "\x13";
$n = strlen($plain_text);
if ($n % 16) $plain_text .= str_repeat("\0", 16 - ($n % 16));
$i = 0;
$enc_text = get_rnd_iv($iv_len);
$iv = substr($password ^ $enc_text, 0, 512);
while ($i < $n) {
$block = substr($plain_text, $i, 16) ^ pack('H*', md5($iv));
$enc_text .= $block;
$iv = substr($block . $iv, 0, 512) ^ $password;
$i += 16;
}
return base64_encode($enc_text);
}
function md5_decrypt($enc_text, $password, $iv_len = 16){
$enc_text = base64_decode($enc_text);
$n = strlen($enc_text);
$i = $iv_len;
$plain_text = '';
$iv = substr($password ^ substr($enc_text, 0, $iv_len), 0, 512);
while ($i < $n) {
$block = substr($enc_text, $i, 16);
$plain_text .= $block ^ pack('H*', md5($iv));
$iv = substr($block . $iv, 0, 512) ^ $password;
$i += 16;
}
return preg_replace('/\\x13\\x00*$/', '', $plain_text);
}
function get_rnd_iv($iv_len){
$iv = '';
while ($iv_len-- > 0) {
$iv .= chr(mt_rand() & 0xff);
}
return $iv;
}
//
// Example:
//
$plain_text = 'very secret string';
$password = 'very secret password';
print "plain text is: [${plain_text}]<br />\n";
print "password is: [${password}]<br />\n";
$enc_text = md5_encrypt($plain_text, $password);
print "encrypted text is: [${enc_text}]<br />\n";
$plain_text2 = md5_decrypt($enc_text, $password);
print "decrypted text is: [${plain_text2}]<br />\n";
Url: http://www.jonasjohn.de/snippets/php/md5-based-block-cipher.htm
Language: PHP | User: ShareMySnippets | Created: Oct 16, 2013