(57 . 7)(57 . 34)
                            Counter : out Interfaces.Unsigned_16;
                            KMgm    : out Keys_Mgm);

  ----------------- File Transfer ----------------------

  -- Writes the given File Chunk to a File Transfer type of message
  -- Chunk - chunk of file to write; contains counter, filename, content
  procedure Write_File_Transfer( Chunk   : in File_Chunk;
                                 Msg     : out Raw_Types.Serpent_Msg);

  -- The opposite of Write_File_Transfer method above.
  -- Chunk will contain the counter, filename and content
  procedure Read_File_Transfer( Msg     : in Raw_Types.Serpent_Msg;
                                Chunk   : out File_Chunk);

  ----------------- File Request  ----------------------
  -- Writes a message to request the files specified through their names
  -- Written parameter will hold the number of filenames actually written
  -- NB: this can be less than the number of filenames provided!
  -- When Written < FR.F_No, the FIRST Written filenames were written; the rest
  -- did not fit into the message and it's up to caller to decide what to do.
  procedure Write_File_Request( FR      : in Filenames;
                                Counter : in Interfaces.Unsigned_16;
                                Msg     : out Raw_Types.Serpent_Msg;
                                Written : out Natural);
  
  -- Reads a request for files; the opposite of Write_File_Request above
  -- Raises Invalid_Msg exception if the provided message fails checks.
  procedure Read_File_Request( Msg      : in Raw_Types.Serpent_Msg;
                               Counter  : out Interfaces.Unsigned_16;
                               FR       : out Filenames);

  ------------------
  -- RSA Messages --
(90 . 12)(117 . 20)

  -- Reads a Key management structure from the given RSA Message
  -- The opposite of Write_KMgm_SMsg above
  -- Raises Invalid_Message exception if given message fails sanity checks
  -- Raises Invalid_Msg exception if given message fails sanity checks
  procedure Read_KMgm_RMsg( Msg     : in Raw_Types.RSA_Msg;
                            Counter : out Interfaces.Unsigned_16;
                            KMgm    : out Keys_Mgm);


  -- String to Octets conversion
  -- NB: Str'Length has to be EQUAL to Octets'Length!
  procedure String_To_Octets(Str: in String; O: out Raw_Types.Octets);

  -- Octets to string conversion
  -- NB: Str'Length has to be EQUAL to Octets'Length!
  procedure Octets_To_String(O: in Raw_Types.Octets; Str: out String);

private
  
  -- if native is little endian, does nothing;
(103 . 6)(138 . 10)
  -- (strictly for arrays of octets)
  procedure Cast_LE( LE: in out Raw_Types.Octets );

  -- separator used for list of filenames
  F_Sep: constant String := ";"; --as string
  Sep: constant Interfaces.Unsigned_8 := 16#3B#; -- ascii code

  -- protocol message types IDs, fixed as per protocol specification
  -- Serpent messages end in "S_Type" 
  -- RSA messages end in "R_Type"
(164 . 4)(203 . 24)
                       Counter : out Interfaces.Unsigned_16;
                       KMgm    : out Keys_Mgm);

  -- helper methods to read/write a value on 16 bits (using Cast_LE as needed)

  -- Writing a 16-bits value to the given Octets at specified position.
  -- NB: Caller has to make sure Pos <= Msg'Last -1 ; NO check here!
  -- Msg - the array of octets into which the value is to be written
  -- Pos - the position in Msg at which to write the value;
  --       NB: Pos will be increased by 2 after the write!
  -- U16 - the value to write
  procedure Write_U16( Msg: in out Raw_Types.Octets;
                       Pos: in out Natural;
                       U16: in Interfaces.Unsigned_16);

  -- Reading a 16-bits value from the given Octets at specified position.
  -- NB: Caller has to make sure Pos <= Msg'Last -1 ; NO check here! 
  -- Pos - the position in Msg from which to read the value;
  --       NB: Pos will be increased by 2 after the read!
  -- The opposite of Write_U16 above.
  procedure Read_U16( Msg: in Raw_Types.Octets;
                      Pos: in out Natural;
                      U16: out Interfaces.Unsigned_16);
end Messages;