> Ample information, including documentation, installation > instructions, > and project details, is available at: > > * https://www.wireguard.com/ > * https://www.wireguard.com/papers/wireguard.pdf In your paper you say this: > Finally, WireGuard is cryptographically opinionated. It intentionally > lacks cipher and protocol agility. If > holes are found in the underlying primitives, all endpoints will be > required to update. The only thing that's certain (beyond death and taxes) is that your crypto choice will one day need updating; either in response to an urgent CVE because an algorithm is compromised or in response to a less urgent one because it is deprecated. Assuming wireguard is reasonably successful we'll have a large ecosystem dependent on it. On this day, we're going to have the choice of either breaking the entire ecosystem by rolling out a change that can't connect to lower protocol versions or trying to wedge version agility into wireguard in a hurry. The former is too awful to contemplate because of the almost universal ecosystem breakage it would cause and the latter is going to lead to additional bugs because people in a hurry aren't as careful as they should be. Could we please build planning for this crypto failure day into wireguard now rather than have to do it later? It doesn't need to be full cipher agility, it just needs to be the ability to handle multiple protocol versions ... two should do it because that gives a template to follow (and test version to try to find bugs in the implementation). It looks like the protocol could simply be updated to put the version into one (or more) of the three reserved bytes in the handshake headers, so perhaps doing this before they get used for something else would be a good first step? James
