doubts on internal representation of key triples “types"

[thomas-fossati]

A couple of questions about the internal representation of key triples:

typed-crypto-key = {
  key: $crypto-key-type-choice
  ? key-type: uint .bits key-type
}

key-type = &(
  attest-key: 0
  identity-key: 1
)

1. Why is the key-type optional? What is the default?
2. Why is key-type a bitmask? Is this a case of compression?

[yogeshbdeshpande]

1. There are cases, when the key-type is not known, hence it is optional.
2. It follows the original pattern of cm-type, but this can be changed, if there is an additional comparison complexity and hence a bottleneck for implementors.