| From: | Paul Hill |
| Date: | 2 Aug 2000 at 14:18:39 |
| Subject: | Re: Programming encryption (poss OT) |
Kevin Fairhurst wrote:
>
> On Wed, 02 Aug 2000 11:30:23 -0000, Adam Bell (adambell@connectfree.co.uk) wrote:
>
> > The part I have forgotten is the boolean operation section. It must
> > work so that the same boolean operation can be used to convert the
> > coded letter back to its original form. As far as I can remember,
> > the binary value of the letter to be coded is NOT'd first and then
> > another operation such as AND OR or XOR etc is then applied.
> >
> > Any help, and sorry if too OT.
>
> You XOR against high values.
>
> (in Hex)
>
> FF Xor $Hex(MyLetter) = CodedLetter
>
> FF Xor $Hex(CodedLetter) = MyLetter
>
> It's not very secure though, now is it? ;)
It can be. The trick is to not use FF but a pseudo-random sequence generated
from a password. If this sequence is long enough (say 2^128) then the
encryption is very good.
This is pretty much how the best encryption schemes work.
Quote carefully and read all ADMIN:README mails