Choose appropriate default algorithms for the given key types

[phish108]

The tools should not require that algorithms are explicity mentioned. Instead sign and encrypt should select suitable defaults if alg or enc are missing.

[phish108]

The tools should be able to select appropriate keys based on their use and the appropriate alg based on the related key's alg property.

[phish108]

This may not always be possible, depending on the token and the key-store.