[sldev] Cryptographic signing of UDP packets

[Argent Stonecutter]

On 2008-12-16, at 05:35, Robin Cornelius wrote:
> Is this going to be ALL UDP packets or just certain ones that are
> certainly more sensitive than others? Not applying to all still leaves
> a potential attack point but wastes bandwidth. This is also related to
> the size of the signature. If the signature is too small a brute force
> attack may be possible by just trying combinations of packets and
> getting a reply from the server, too large a signature and we have
> massive UDP packets so more bandwidth and lag?

If you instead encrypt the UDP packets you won't need to add a  
signature to the packet itself, you can just encrypt the packet with a  
key passed through HTTPS CAPS at login. The computational overhead  
should be similar for encryption or signing at equivalent levels of  
security, and encryption would add privacy.

Since you have a secure channel via HTTPS, you don't need to use a  
separate key exchange protocol, and you don't need the computational  
overhead of private keys.

In fact just periodically exchanging a UUID over HTTPS to use in some  
fast short-period encryption technique would probably be enough. Don't  
serialize the packets, just keep updating the key.