(12 . 6)(12 . 10)
  -- no side effects or internal state
  Pragma Pure(Raw_Types);

  -- raw, low-level type
  -- all messages and packets are simply arrays of octets at low level/raw
  type Octets is array( Natural range <> ) of Interfaces.Unsigned_8;

  -- constants from SMG.COMMS standard specification

    -- RSA key size in octets
(21 . 22)(25 . 29)
    -- a. it's C code that should import this, not the other way around.
    -- b. it needs to be static here.
  RSA_KEY_OCTETS : constant Positive := 490;
    
    -- OAEP constants: defined here as still part of standard spec.
    -- OAEP package will use those values when using Raw_Types
    -- (NOT the other way around since dependency is oaep on types.)
  OAEP_R_STR     : constant String  := "TMSR-RSA";
    -- "TMSR-RSA" as unsigned_8 values:
  OAEP_RESERVED  : constant Octets  := (84,77,83,82,45,82,83,65);
    -- max length of useful payload in a OAEP-encrypted entity
  OAEP_MAX_LEN   : constant Natural := RSA_KEY_OCTETS / 2 - 
                                           OAEP_R_STR'Length - 3;

    -- size of a RSA-encrypted packet and message in octets and bits
  RSA_PKT_OCTETS : constant Positive := 1470;
  RSA_MSG_OCTETS : constant Positive := RSA_PKT_OCTETS / 
                                          RSA_KEY_OCTETS *
                                            OAEP_MAX_LEN;
  RSA_MSG_BITS   : constant Positive := RSA_MSG_OCTETS * 8; 

    -- size of a serpent-encrypted packet and message, in octets
    -- note that this corresponds to 1472/16 = 92 Serpent blocks
    -- NB: lengths are the same!
  SERPENT_OCTETS : constant Positive := 1472;

    -- size of a RSA-encrypted packet and message in octets and bits
  RSA_PKT_OCTETS     : constant Positive := 1470;
  RSA_MSG_OCTETS     : constant Positive := 234;
  RSA_MSG_BITS       : constant Positive := RSA_MSG_OCTETS * 8; --1872

  -- raw, low-level types
  -- all messages and packets are simply arrays of octets at low level/raw
  type Octets is array( Natural range <> ) of Interfaces.Unsigned_8;

  -- raw representations of basic types (with fixed, well-defined sizes)
  subtype Octets_1 is Octets( 1 .. 1 );
  subtype Octets_2 is Octets( 1 .. 2 );