[SOLVED] Simple Encryption/Decryption?

[Michdd]

How could I make a simple encryption that would encrypt a string, but I could decrypt it back with a different script.

[blueman378]

it really depends on you.

 

i mean if you really wanted you could do something simple like assign a=1 b=2 ect

 

then count the string length  add that onto each number

and then change the string to the numbers.

 

decrypt it by reversing lol

[corbin]

Think if encryption as a function, and think of decrypting as the inverse of said function.

 

 

For example, if f(1) = 3, then f^-1(3) should = 1.  (f^-1 meaning opposite of f.)

 

 

 

So, you'll essentially need to come up with something that can be reversed, but not done so easily.  You could use a key to encrypt it against, or you could just change the value or what ever.

 

 

 

Or, you could use some of the algorithms already out there.

[Michdd]

it really depends on you.

 

i mean if you really wanted you could do something simple like assign a=1 b=2 ect

 

then count the string length  add that onto each number

and then change the string to the numbers.

 

decrypt it by reversing lol

 

How could I make something that would change all, for example, a's to 3, within a certain string?

[blueman378]

regex

[blueman378]

it really depends on you.

 

i mean if you really wanted you could do something simple like assign a=1 b=2 ect

 

then count the string length  add that onto each number

and then change the string to the numbers.

 

decrypt it by reversing lol

 

How could I make something that would change all, for example, a's to 3, within a certain string?

 

regex

[DarkWater]

Horrid ideas. >_>  Just use simple XOR encryption.  I wrote up a quick set of functions for you:

 

<?php
function xor_crypt($input, $key) {
$input_l = strlen($input);
$key_l = strlen($key);
for ($i=0;$i<$input_l;$i++) {
	$pos = $i % $key_l;
	$input[$i] = chr(ord($input[$i]) ^ ord($key[$pos]));
}
return $input;
}

function do_encrypt($input, $key) {
$input = xor_crypt($input, $key);
$input = base64_encode($input);
return $input;
}

function do_decrypt($input, $key) {
$input = base64_decode($input);
$input = xor_crypt($input, $key);
return $input;
}

 

Usage:

<?php
$string = "JUST some RANDOM string going on here.... >_>";
$key = "ASHD77278qu389*A*S*D0a)))(ASdjuio!$^$RHF";
$enc = do_encrypt($string, $key);
echo "$enc\n";
echo do_decrypt($enc, $key) . "\n";