[sldev] Cryptographic signing of UDP packets

[Argent Stonecutter]

The proposed solutions are these:

1. add a signature to each packet.
2. encrypt each packet
3. transfer money-related packets over SSL
4. wrap the entire session in an IPSEC layer

Of these, I think option 3 is most secure, most standards-compliant,  
and lowest overhead. It would also be likely to increase the  
reliability of money transactions at the cost of some increased  
latency. Since money transactions are not real-time events, and even  
many seconds of additional latency is acceptable, there's no reason  
not to use it.