initial_salt = 0x38762cf7f55934b34d179ae6a4c80cadccbb7f0a
initial_secret = HKDF-Extract(initial_salt,
                              client_dst_connection_id)

client_initial_secret = HKDF-Expand-Label(initial_secret,
                                          "client in", "",
                                          Hash.length)
server_initial_secret = HKDF-Expand-Label(initial_secret,
                                          "server in", "",
                                          Hash.length)