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------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- G N A T . S E C U R E _ H A S H E S . S H A 2 _ C O M M O N --
-- --
-- B o d y --
-- --
-- Copyright (C) 2009, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
package body GNAT.Secure_Hashes.SHA2_Common is
---------------
-- Transform --
---------------
procedure Transform
(H_St : in out Hash_State.State;
M_St : in out Message_State)
is
use System;
subtype Word is Hash_State.Word;
use type Hash_State.Word;
function Ch (X, Y, Z : Word) return Word;
function Maj (X, Y, Z : Word) return Word;
pragma Inline (Ch, Maj);
-- Elementary functions from FIPS PUB 180-3
--------
-- Ch --
--------
function Ch (X, Y, Z : Word) return Word is
begin
return (X and Y) xor ((not X) and Z);
end Ch;
---------
-- Maj --
---------
function Maj (X, Y, Z : Word) return Word is
begin
return (X and Y) xor (X and Z) xor (Y and Z);
end Maj;
type Words is array (Natural range <>) of Word;
X : Words (0 .. 15);
for X'Address use M_St.Buffer'Address;
pragma Import (Ada, X);
W : Words (0 .. Rounds - 1);
A, B, C, D, E, F, G, H, T1, T2 : Word;
-- Start of processing for Transform
begin
if Default_Bit_Order /= High_Order_First then
for J in X'Range loop
Hash_State.Swap (X (J)'Address);
end loop;
end if;
-- 1. Prepare message schedule
W (0 .. 15) := X;
for T in 16 .. Rounds - 1 loop
W (T) := S1 (W (T - 2)) + W (T - 7) + S0 (W (T - 15)) + W (T - 16);
end loop;
-- 2. Initialize working variables
A := H_St (0);
B := H_St (1);
C := H_St (2);
D := H_St (3);
E := H_St (4);
F := H_St (5);
G := H_St (6);
H := H_St (7);
-- 3. Perform transformation rounds
for T in 0 .. Rounds - 1 loop
T1 := H + Sigma1 (E) + Ch (E, F, G) + K (T) + W (T);
T2 := Sigma0 (A) + Maj (A, B, C);
H := G;
G := F;
F := E;
E := D + T1;
D := C;
C := B;
B := A;
A := T1 + T2;
end loop;
-- 4. Update hash state
H_St (0) := A + H_St (0);
H_St (1) := B + H_St (1);
H_St (2) := C + H_St (2);
H_St (3) := D + H_St (3);
H_St (4) := E + H_St (4);
H_St (5) := F + H_St (5);
H_St (6) := G + H_St (6);
H_St (7) := H + H_St (7);
end Transform;
end GNAT.Secure_Hashes.SHA2_Common;
|
