Need pointed in right direction Serial generation

This is what I want to do in php.

This is an example:

--------- Keygenerator.php


Use A Seed Key: 10952783587 <- any of my choosing
Enter a Name: billy bob



---------

result:

Name: billy bob
Key: 7319C0258CD6502BFFFEC44D


In a decrypte.php

enter 7319C0258CD6502BFFFEC44D

to get the original name: billy bob


can this be done?


jobesd

How good does the encryption need to be? Here's a fast and dirty one, but not too hard to break if you know what to look for and you have at least one sample of a before and after value:

for each letter in your key, do a binary xor against the corrasponding letter in your input value. If key runs out of characters, start again from the first character. Take end results, convert to Hex (since it can end up being any value)

To reverse, convert hex to string, and xor against your key again.

The only problem with this, is if someone knows both the start and end values, they can xor them against each other to get your key.

I use this method for encrypting files on my HD (without the hex conversion) since no one could possibly know the before value. (even the file name is encrypted)

I think that I can do it this way. I am using base64 encoding with a variety of encoding,slicing and dicing, rencoding and an eregi at the end.

seed key "0123456789";
name = "My Name";

cryptkey1 = "1268469bGr4576KfRGVD22307"
cryptkey2 = "5lu7s3fg5ll8591311lygfd"
cryptkey3 = "kl582fg69hjlddWNgf458FF12886"


after doing what I do I get this serial. to decrypt I just do a reverse order of the steps.


serial =



decrypted = My Name



I just don't know how secure it would be using this method. I don't have mcrypt available.

If I wanted to xor two serials like above together how could I do that?

I figure if I can make the scheme screewy and enough steps I can really make it difficult.


jobesd

I don't know about PHP, but to xor two values in Perl or C, you just do:

newval=oldval[x]^key[x];

The "^" character is the binary xor operator.