P256.NoallocVersions of these functions which write their output in a buffer passed in as an argument
raw_to_compressed p result converts a "raw" point p (64 bytes) to a "compressed" point result (33 bytes).
raw_to_uncompressed p result converts a "raw" point p (64 bytes) to an "uncompressed" point result (65 bytes).
compressed_to_raw p result converts a "compressed" point p (33 bytes) to a "raw" point result (64 bytes). Returns true if successful.
uncompressed_to_raw p result converts an "uncompressed" point p (65 bytes) to a "raw" point result (64 bytes). Returns true if successful.
ECDH key agreement protocol
dh_initiator sk pk takes a 32-byte secret key sk and writes the corresponding 64-byte public key in pk.
dh_responder sk pk shared takes a 32-byte secret key sk and another party's 64-byte public key and writes the 64-byte ECDH shared key in shared. Buffer shared must be distinct from pk.