Ceaser Cipher

drawmack

I'm still bored so I made up a ceaser cipher in php.

Here is the function

function ceaser($clicks,$input) {
    //set output to stop errors from showing
    $output = "";

//get the length of the string once to aid in efficency
$str_len = strlen($input);

//encryption loop
for($i=0;$i<$str_len;$i++) {
    //get the ascii value of the current character
    $cur_char = ord(substr($input,$i,1));

    //if this is an upper case letter
    if($cur_char > 64 && $cur_char < 91) {
        //turn the letter into its position in the alphebet
        $cur_char = $cur_char - 65;
        //move the position according to clicks and turn the position
        //back into the value of the ascii letter
        $cur_char = ($cur_char + $clicks)%26 + 65;

    //if this is a lower case letter 
    } elseif ($cur_char > 96 && $cur_char < 123) {
        //turn the letter into its position in the alphebet
        $cur_char = $cur_char - 97;
        //move the position according to clicks and turn the position
        //back into the value of the ascii letter
        $cur_char = ($cur_char + $clicks)%26 + 97; 
    } //end if

    $output .= chr($cur_char);
} //end for
return $output;
} //end rot13

the attachment is a complete working example

marque

yhub fxwh gudzpdfn!

Moonglobe

so is this just a rot13 implentation? 'cuz there is [man]str_rot13/man....

laserlight

Not quite.

str_rot13() is a special case of a Caesar cipher.

drawmack

rot13 is a ceaser cipher with a key of 13, this is a generic implementation of the cesear cipher where you can use any number of clicks.

Moonglobe

o of course lol, ya wasn't thinkin straight. thanks for clearing that up 🙂

drawmack

Originally posted by marque
yhub fxwh gudzpdfn!

I finally got around to programming the chi square attack on the ceaser cipher.

Tanslation: very cute drawmack!

with a key of 3, which is the classic ceaser cipher, very cute marque

procoder

Well done drawmack

One suggestion

change

function ceaser($clicks,$input) {

function ceaser($input, $clicks = 13) {

Just incase no clicks specified, it uses rot13 actully.

so people can just do ceaser('bla') for defautt cypher

drawmack

Originally posted by procoder
function ceaser($input, $clicks = 13) { 
Just incase no clicks specified, it uses rot13 actully.
so people can just do ceaser('bla') for defautt cypher [/B]

Actually since the original Ceaser cipher used 3 clicks then shouldn't I set the clicks to 3 if I'm going to default it?

The reason I didn't default it is because it's more flexible this way. I can define the default clicks in the calling code without changing the function at all.