Re: [Algorithms] Message signature in token ring

[Space N. E. P. <SPA...@ho...>]

Thanks for your help.

How do people generate these really prime large numbers and relative primes,
anyway? Simple brute force? Does the choice of prime numbers affect the
security of the algorithm? (Does their magnitude affect the security?)

I know that it's a hard problem, but I'm not using these communications as
any sort of pervasive fundamental protocol in a game. The communication is
important, but low frequency, and its disruption is only a nuisance - it
won't allow you to access anything you're not supposed to be able to, it
won't give you any powers you don't have. But like I said, it's important
enough that I can't just leave it unguarded. The parameters you list below
are all true, but every peer-to-peer file sharing network suffers from those
same problems, and yet they continue to run. Why? If you hack, at best all
you can be is uncooperative and disrupt communication in some locality and
create spam. There's nothing to gain; it gets old. In other words, humor me
and let me follow this mostly academic pursuit. :^)

snx

----- Original Message -----
From: "Dave Moore" <dm...@od...>
To: <gda...@li...>
Sent: Tuesday, April 15, 2003 11:31 AM
Subject: Re: [Algorithms] Message signature in token ring


> Space Needle Exchange Program wrote:
> >
> [...]
> > know. But you can explain more what you meant by "RSA's minimum
> > message length is the length of the modulus"?
>
>   Here's a concise description of the algorithm.
> http://www.pvv.ntnu.no/~asgaut/crypto/thesis/node18.html.  In step 4,
> you can see that the ciphertext is going to be a number between 0 and
> PQ, the modulus.  For secure moduli sizes, (512 bits for security
> against a college student with access to a campus full of computers)
> this is a pretty large overhead, which is why products like PGP use
> public key algorithms only to transport keys for symmetric algorithms.
> 256 bits is a really low number for RSA.  It's about an 80 digit number
> which could be factored probably in a couple of days by someone who had
> access to just a few decent computers.
>
>   Honestly, you should forget about all of this.  You'll get it wrong.
> This is not a statement about your coding skills, because EVERYONE gets
> it wrong.  Security is a REALLY hard problem to solve correctly, and
> you've got just about the hardest case there is.  (P2P, no authoritative
> server, minimal precommunication between peers, full executable
> available to hackers, packets explicitly handed to people for
> man-in-the-middle attacks.)  Your time is much better spent making a
> game that people want to hack... :)
>
> ...dave
>
>
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