dc wrote:
> I need to encode some data with a userID and then also be able to
>  decode it with the same key.
> This is basically a quick approach to obfuscate URLs. Its for an 
> environment where we know the users ID with some degree of
> certainty.

Simple obfuscation can be done by XORing a keyword. On a binary layer
this works as follows:

Calling Key K, Original messages O, transmitted Message T here's a
binary example:

K = 1010
V = 1001010111101001

1001010111101001
1010101010101010
0011111101000011

T = 0011111101000011

In this particular encoding is not secure because K is not random and
much shorter than V. In contrast to false rumors XOR coding is not
inherently insecure. Quite the opposite is true: When K is perfectly
random and at least as long as V the coding is the only one known to
mankind that can be mathematically proved to be unbreakable.
According to certain sources the XOR encoding with perfectly random K
 is used for the launch command for nuclear SMBs (submarine based
missiles). That may be an uran legend. A fact is that many programs
that allow you to password-encode a file actually XOR the file's
content with the Password. Which means that a more random and longer
passwords results in a more secure encoding.

じゃまた、

Jupp