[sldev] Cryptographic signing of UDP packets

[Tateru Nino]

The current protocol would mean that you couldn't rely on any cipher
block-chaining, mind. The packets can arrive out of order, and it is not
critical if some are missed, as currently specified - but the overhead
for a simple symmetrical cipher with a periodic key-exchange would be
quite low.

Argent Stonecutter wrote:
> 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.
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