The Grapevine Project

Stephen Blackheath stephen@blacksapphire.com
Thu, 6 Dec 2001 13:13:28 +1300


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Steve,

On Thu, 06 Dec 2001 13:00, you wrote:
> Stephen Blackheath wrote:
> > We use a 'hash cash' technique
> > (which we call "Solve A Hard Problem") for defence against
> > denial-of-service attacks - the assumption being that legitimate nodes
> > have more CPU power than attackers.
>
> that seems like a silly assumption. What about DDoS?

Firstly, understand that when I say "legitimate nodes have more CPU power", I 
am referring to the sum of all legitimate nodes vs. the sum of all attackers.

Ultimately, if an attacker has more of something than you do, then the 
attacker will win.  The only thing you have control over as designer is what 
that something is.  We chose CPU time rather than network bandwidth or access 
to IP addresses, because none of the strategies relating to the latter things 
seemed to work.  I am certainly open to better ideas.

DDoS - if you're talking about it as an attack from nodes outside the network 
- - is difficult against the Grapevine due to the high cost of 'harvesting' IP 
addresses.

As for attacks by worms infecting the machines that make up the network, we 
simply cannot defend against that.  I don't think any network can.  (The 
Internet itself doesn't have this problem, because its routing takes place on 
secure hardware.)


Steve
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see http://www.gnupg.org

iD8DBQE8Drgo7I0ehz47OHERAhCMAJ4yIoedtb9Bt//x3102iE5gdxTbhACeOsgk
Q3VtO/QOCEwvLBpE3nDBHSU=
=EpFN
-----END PGP SIGNATURE-----