kragen@pobox.com wrote:
> Jeff Bone <jbone@jump.net> writes:
> > > Of course, if you're up against a big enemy, and they know the type of
> > > observation you're doing then they can do the equivalent of a brute force
> > > search (record all TV stations, measure all stars, etc.).
> >
> > That's essentially the same as "generate all possible one-time pads of form X." If
> > you can make the problem that hard for "them," you've won. ;-)
>
> It's not at all essentially the same, although you may be correct that
> it's good enough. If you find a star that decrypts the message to
> something sensible, you can be pretty sure the decryption was correct;
> that's not at all true of one-time pads.
You're missing the point. It's not just about finding the star, it's about finding the
time interval in which the observations yielded the keypad bitstring in question. (I.e.,
it's not assumed that the star in question / source of bits repeats.) Only two
approaches are possible: record all data for all stars and try all bit substrings of
those, which are bound in size only by knowing (a) the earliest time the system was
deployed and / or earliest possible recorded observations, and (b) the latest possible
bitstring position that could've been used (from the time of the message intercept) OR
generate all possible bitstrings.
Cf. my "Crypto" message. Some guy at Hahvahd is poking at this, too.
jb
>
>
> The imaginable --- the space of one-time pad keys --- is unimaginably
> larger than the universe.
>
> > BTW, my posting this was simply to document that it's been thought
>
> This is a major reason for kragen-tol --- unfortunately, as far as I
> know, nobody but me is maintaining archives of it.
This archive was generated by hypermail 2b29 : Fri Apr 27 2001 - 23:17:58 PDT