I set myself a chalange last year (purley for fun) to write an encryption cypher without using someone elses code or without using the same methods. After researching the different types of encryption cyphers that are out there, I decided to go with a Symmetric Encryption cypher.
Symmetric Encryption cyphers basicaly use a key (word, phrase or string) to encrypt and decrypt the input and output data.
The code that I have wrote below is by no means bullet proof or useable in every environment (talking along the lines of encoding and characters).
Im not going to write much more on this as the code is not fully tested but does work I asure you. The code will encrypt and decrypt lower case, upper case, numerical and all special characters found on an english/american key pad.
<?php
header('Content-Type: text/html; charset=utf-8');
function ACT_encrypt_cipher($str, $key){
if( is_string($str) && is_string($key) ) {
$str = mb_convert_encoding($str, 'HTML-ENTITIES', "UTF-8");
$sl = strlen($str); $kl = strlen($key);
$fk = str_split(str_repeat($key, ceil($sl/$kl)));
$es = ' abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789&;:[]<>!"$%^*_-=+.,/\\()@?\'`';
$ea = array( 'a' => array(), 'm' => array(), 'c' => array());
foreach( str_split( $es ) as $key => $char ) { $ea['a'][] = $key; $ea['m'][] = md5($char); $ea['c'][] = $char; }
$ns = '';
$sp = str_split($str);
foreach( $fk as $k => $_char ) {
if( ! isset( $sp[$k] ) ) break;
$cm = md5($sp[$k]);
if( in_array( $cm, $ea['m'] ) ) {
$kk = array_keys( $ea['m'], $cm );
if( in_array( md5($_char), $ea['m'] ) ) {
$sk = array_keys( $ea['m'], md5($_char) );
$n = $ea['a'][$kk[0]] - $ea['a'][$sk[0]];
if( $n < 0 )
$n = $n + (strlen($es));
$ns .= $es[$n];
}else
$ns .= $_char;
}else
$ns .= $_char;
}
return $ns;
}
}
function ACT_decrypt_cipher($str, $key){
if( is_string($str) && is_string($key) ) {
$str = mb_convert_encoding($str, 'HTML-ENTITIES', "UTF-8");
$sl = strlen($str); $kl = strlen($key);
$fk = str_split(str_repeat($key, ceil($sl/$kl)));
$es = ' abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789&;:[]<>!"$%^*_-=+.,/\\()@?\'`';
$ea = array( 'a' => array(), 'm' => array(), 'c' => array());
foreach( str_split( $es ) as $key => $char ) { $ea['a'][] = $key; $ea['m'][] = md5($char); $ea['c'][] = $char; }
$ns = '';
$sp = str_split($str);
foreach( $fk as $k => $_char ) {
if( ! isset( $sp[$k] ) ) break;
$cm = md5($sp[$k]);
if( in_array( $cm, $ea['m'] ) ) {
$kk = array_keys( $ea['m'], $cm );
if( in_array( md5($_char), $ea['m'] ) ) {
$sk = array_keys( $ea['m'], md5($_char) );
$n = $ea['a'][$kk[0]] + $ea['a'][$sk[0]];
if( $n > (strlen($es)-1) )
$n = $n - strlen($es);
$ns .= $es[$n];
}else
$ns .= $_char;
}else
$ns .= $_char;
}
return $ns;
}
}
$keyd = 's3cr3t';
$str = 'Me `and` my "email" [foo@example.co.uk], website (http://www.example.co.uk) went 4 a\ walk WHICH I might add cost \'£0.00\' (or $0.00?).';
$en = ACT_encrypt_cipher($str, $keyd);
$de = ACT_decrypt_cipher($en, $keyd);
echo "<strong>String:</strong> $str<br />";
echo "<strong>Encrypted:</strong> " . htmlentities($en) . "<br />";
echo "<strong>Decrypted:</strong> $de";
?>
The output would be:
String: Me `and` my "email" [foo@example.co.uk], website (http://www.example.co.uk) went 4 a\ walk WHICH I might add cost '£0.00' (or $0.00?).
Encrypted: tM?"I(*G?)6!ZMj%Q/ZH&=W)]Mu%U@\M-*W7bS;&Hc_Jp,1*"Beb1@Tz+e4c8Mu%U@\M-*W7bS/$4*)1?MH";Ht%T,"\Eq&n">?)Q-+1?%L^"Kla1!>gx*Q'^h7'Wa)L8IxGHF?[W'"pX9?G<C-
Decrypted: Me `and` my "email" [foo@example.co.uk], website (http://www.example.co.uk) went 4 a\ walk WHICH I might add cost '£0.00' (or $0.00?).
