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smg_comms_packing...    1   -- Packing/unpacking for Eulora's communication protocol:
smg_comms_packing...    2   -- Serpent Message to/from Serpent Packet
smg_comms_packing...    3   -- RSA Message to/from RSA Packet
smg_comms_packing...    4   -- S.MG, 2018
smg_comms_packing...    5 
smg_comms_packing...    6 package body Packing is
smg_comms_packing...    7 
smg_comms_packing...    8   -- Packing a Serpent message into Serpent package, using the given key
smg_comms_packing...    9   function Pack( Msg : in Raw_Types.Serpent_Msg;
smg_comms_packing...   10                  K   : in Serpent.Key ) 
smg_comms_packing...   11                return Raw_Types.Serpent_Pkt is
smg_comms_packing...   12 
smg_comms_packing...   13     -- single Serpent blocks containing plain / encrypted data
smg_comms_packing...   14     Plain    : Serpent.Block;
smg_comms_packing...   15     Encr     : Serpent.Block;
smg_comms_packing...   16 
smg_comms_packing...   17     -- Serpent Key Schedule - needed for direct encr/decr calls
smg_comms_packing...   18     KS       : Serpent.Key_Schedule;
smg_comms_packing...   19 
smg_comms_packing...   20     -- final resulting Serpent package
smg_comms_packing...   21     Pkt      : Raw_Types.Serpent_Pkt := (others => 0);
smg_comms_packing...   22   begin
smg_comms_packing...   23     -- prepare the Serpent key schedule based on given key
smg_comms_packing...   24     Serpent.Prepare_Key( K, KS );
smg_comms_packing...   25 
smg_comms_packing...   26     -- encrypt message block by block and copy result in packet
smg_comms_packing...   27     for I in 1 .. S_Blocks loop
smg_comms_packing...   28       -- get current block to encrypt
smg_comms_packing...   29       Plain := Msg( Msg'First + (I-1) * Block_Len .. 
smg_comms_packing...   30                     Msg'First +  I    * Block_Len - 1 );
smg_comms_packing...   31       -- encrypt with Serpent
smg_comms_packing...   32       Serpent.Encrypt( KS, Plain, Encr );
smg_comms_packing...   33       -- copy result to output packet
smg_comms_packing...   34       Pkt( Pkt'First + (I-1) * Block_Len ..
smg_comms_packing...   35            Pkt'First +  I    * Block_Len - 1 ) 
smg_comms_packing...   36          := Encr;
smg_comms_packing...   37     end loop;
smg_comms_packing...   38 
smg_comms_packing...   39     -- return result
smg_comms_packing...   40     return Pkt;
smg_comms_packing...   41   end Pack;
smg_comms_packing...   42 
smg_comms_packing...   43   -- Unpacking a Serpent packet into contained message, using the given key
smg_comms_packing...   44   function Unpack( Pkt : in Raw_Types.Serpent_Pkt;
smg_comms_packing...   45                    K   : in Serpent.Key) 
smg_comms_packing...   46                  return Raw_Types.Serpent_Msg is
smg_comms_packing...   47     -- single Serpent blocks containing plain / encrypted data
smg_comms_packing...   48     Plain    : Serpent.Block;
smg_comms_packing...   49     Encr     : Serpent.Block;
smg_comms_packing...   50 
smg_comms_packing...   51     -- Serpent Key Schedule - needed for direct encr/decr calls
smg_comms_packing...   52     KS       : Serpent.Key_Schedule;
smg_comms_packing...   53 
smg_comms_packing...   54     -- the message extracted from the given packet
smg_comms_packing...   55     Msg : Raw_Types.Serpent_Msg := (others => 0);
smg_comms_packing...   56   begin
smg_comms_packing...   57     -- prepare the Serpent key for use
smg_comms_packing...   58     Serpent.Prepare_Key( K, KS );
smg_comms_packing...   59 
smg_comms_packing...   60     -- decrypt the Serpent packet block by block
smg_comms_packing...   61     for I in 1 .. S_Blocks loop
smg_comms_packing...   62       -- get current block from input and decrypt
smg_comms_packing...   63       Encr := Pkt( Pkt'First + (I-1) * Block_Len ..
smg_comms_packing...   64                    Pkt'First +  I    * Block_Len - 1 );
smg_comms_packing...   65       Serpent.Decrypt( KS, Encr, Plain );
smg_comms_packing...   66 
smg_comms_packing...   67       -- copy result to its correct position in final output
smg_comms_packing...   68       Msg( Msg'First + (I-1) * Block_Len ..
smg_comms_packing...   69            Msg'First +  I    * Block_Len - 1 )
smg_comms_packing...   70          := Plain;
smg_comms_packing...   71     end loop;
smg_comms_packing...   72 
smg_comms_packing...   73     -- return the result - the message content of given package
smg_comms_packing...   74     return Msg;
smg_comms_packing...   75   end Unpack;
smg_comms_packing...   76 
smg_comms_packing...   77 end Packing;