-- Packing/unpacking for Eulora's communication protocol:
  -- Serpent Message to/from Serpent Packet
  -- RSA Message to/from RSA Packet
  -- S.MG, 2018

with Raw_Types;
with Serpent;
with RSA_OAEP;

package Packing is
  -- no side effects or internal state BUT it depends on non-pure:
  -- rsa_oaep because it uses rng (exceptions and sequential_io)

  -- Packing a Serpent message into Serpent packet, using the given key
  function Pack( Msg : in Raw_Types.Serpent_Msg;
                 K   : in Serpent.Key ) 
                return Raw_Types.Serpent_Pkt;

  -- Unpacking a Serpent packet into contained message, using the given key
  function Unpack( Pkt : in Raw_Types.Serpent_Pkt;
                   K   : in Serpent.Key) 
                  return Raw_Types.Serpent_Msg;

  -- Packing a RSA message into RSA packet, using the given key
  function Pack( Msg : in Raw_Types.RSA_Msg;
                 K   : in RSA_OAEP.RSA_pkey)
                return Raw_Types.RSA_Pkt;

  -- Unpacking a RSA packet into contained message, using the given key
  function Unpack( Pkt     : in Raw_Types.RSA_Pkt;
                   K       : in RSA_OAEP.RSA_skey;
                   Success : out Boolean)
                  return Raw_Types.RSA_Msg;

  -- internals of this package, NOT for outside use
private
  -- length of 1 Serpent block
  Block_Len: constant Natural := Serpent.Block'Length;

  -- number of Serpent blocks in one single Serpent message/packet
  S_Blocks : constant Natural := Raw_Types.SERPENT_OCTETS / Block_Len;

end Packing;