Encryption question.

Anon

I am trying to build a very simple encryption algorithm, for demonstration purposes. Does anybody know of a way to take a string and break it into each of its char elements (just as a string in C or C++ is represented)?

Once I have that down I can use the old "Caesar" crypto trick, add 5 to each char element, and then dencrypt it as I please (using the reverse, e.g. -5 from each char).

Note: what I am after is turning a PHP string into its C++ equivalent (an array of char). Once I have that, anything is possible. But I don't see anything in the PHP library that will do this conversion.

Anon

$string = "hello world";
echo $string[0];

is how you treat strings like char arrays

Anon

Ok, so can I assume then, given your example, that $string[0] == "h", $string[1] == "e", $string[2] == "l", etc. ?

Anon

yes ... then just use str_len function to get the lenght and just loop and +5.

Cheers,

Anon

This guy is more or less correct. Of course you can't just add 5 to the characters, as this will type cast the letter to have the value of 5, he doesn't mean that literally. You actually do it like this:
(note ord() to get the value, chr() to make it a char again.)

function encrypt($string)
{
$cheese = "";
for($i = 0; $i < strlen($string); $i++)
{
$cheese.= chr(ord($string[$i])+5);
}
return $cheese;
}

Anon

Just forgot my "C" roots there for a moment.

Seems to me a much more sophisticated encryption algorithm can then be built by substituting a specific character during the encryption, e.g., a = 'x', b = 'h', c = '8', etc. rather than just adding chr(ord($string[$i])+5), or whatever to each char. Or perhaps the +5 value could be varied, depending upon the inital letter and its position in the alphabet, e.g., for 'a' thru 'e', add 5, for 'f' thru 'j', add 6, etc. Or perhaps each string could even be timed stamped, and the seconds value used to vary the encryption.

This isn't meant to be a very sophisticated encryption scheme, just one good enough to keep the data temporarily safe until I can download it from the server.