Principal are generic identifiers for canisters and users.
raw, _ := hex.DecodeString("abcd01")
p := principal.Principal(raw)
fmt.Println(p.Encode())
// Output:
// em77e-bvlzu-aqThese are always generated by the system and have no structure of interest outside the system. Typically, these end with the byte 0x01.
An external user can use these ids as the sender of a request if they own the corresponding private key.
sha224(public_key) 0x02
Derived IDs are currently not explicitly used, but they may be used internally or in the future.
sha224(len(registering_principal) registering_principal derivation_nonce) 0x03
Used for the anonymous caller. It can be used in call and query requests without a signature.