> And besides, how will you update our map that says that protocol "age" 1 uses rsa, "age" 2 uses ed25519? That's right, with "Registries". Unless you convince

> And besides, how will you update our map that says that protocol "age" 1 uses rsa, "age" 2 uses ed25519? That's right, with "Registries". Unless you convince the whole world to just instantly switch to the new version at the same time, so that you can also drop the old version. There is a not so subtle difference here. Rule: When more than one algorithm is implemented in a protocol, negotiation is unavoidable. What you can choose is to do one of two things: 1. Run-Time Negotiation --- Within a given version of a protocol, you can have multiple simultaneous in-flight algorithms, modes, key sizes, etc. at play. 2. Compile-Time Negotiation -- Version 1 only does Algorithm ABC with config XYZ, Version 2 does Algorithm DEF with config VXW. You cannot get version 1 with another algorithm. (I use "Compile-Time" somewhat hand-wavy here; some programming languages are interpreted instead of compiled.) It should be plainly obvious why option 1 is more dangerous and harder to prove secure than option 2.