This function does not check that the resulting pk is valid. It is slightly faster than pk_of_bytes but should only be used to deserialize bytes that were serialized from a pk. E.g. the pks in the storage of the protocol.
keypair generates both a secret key and its corresponding public key
to_bytes key returns the contents of the key. For P-256 public keys, it returns the compressed form (see hacl.ml for more details)
blit_to_bytes key ?pos buf copies all of the bytes of
buf starting at position
pos. As above, P-256 public keys are written in compressed form.