So I’m doing some work on extending BIP85 functionality on SeedSigner to include GPG key generation, file verification, encrypted messaging, etc, but the resource limitation on low power devices like the Raspberry Pi really makes RSA keys quite painful to use at any useful bit length. (RSA3072 takes 15-20 minutes for a primary key + 3 subs)
Basically I’m suggesting an expansion of the current functionality to add support for some common ECC curves and provide a bit of a process for future curves to be added in a way that doesn’t break existing implementations. (The simplest solution is to just use ECC with key length on the existing RSA derivation, but that doesn’t seem very consistent with how BIP85 works for other similar use cases where the derivation path should tell you everything you need to know about the output data/entropy/usage)
While it would have been nice to have a separate derivation level for key_type, that ship has probably sailed, so rather than add that, I am just suggesting a different applicationID for each key type. (Similar to how variations are handled with the existing password application type)
While I’m at it, I’m also suggesting some information about how additional and mixed key types should be handled.
Anyway, just keen to get some input on a way forward, can add some additional test vectors and stuff once others have provided some input about a preferred way forward.
