File : g-shshco.adb
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT LIBRARY COMPONENTS --
4 -- --
5 -- 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 --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 2009, Free Software Foundation, Inc. --
10 -- --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 package body GNAT.Secure_Hashes.SHA2_Common is
33
34 ---------------
35 -- Transform --
36 ---------------
37
38 procedure Transform
39 (H_St : in out Hash_State.State;
40 M_St : in out Message_State)
41 is
42 use System;
43
44 subtype Word is Hash_State.Word;
45 use type Hash_State.Word;
46
47 function Ch (X, Y, Z : Word) return Word;
48 function Maj (X, Y, Z : Word) return Word;
49 pragma Inline (Ch, Maj);
50 -- Elementary functions from FIPS PUB 180-3
51
52 --------
53 -- Ch --
54 --------
55
56 function Ch (X, Y, Z : Word) return Word is
57 begin
58 return (X and Y) xor ((not X) and Z);
59 end Ch;
60
61 ---------
62 -- Maj --
63 ---------
64
65 function Maj (X, Y, Z : Word) return Word is
66 begin
67 return (X and Y) xor (X and Z) xor (Y and Z);
68 end Maj;
69
70 type Words is array (Natural range <>) of Word;
71
72 X : Words (0 .. 15);
73 for X'Address use M_St.Buffer'Address;
74 pragma Import (Ada, X);
75
76 W : Words (0 .. Rounds - 1);
77
78 A, B, C, D, E, F, G, H, T1, T2 : Word;
79
80 -- Start of processing for Transform
81
82 begin
83 if Default_Bit_Order /= High_Order_First then
84 for J in X'Range loop
85 Hash_State.Swap (X (J)'Address);
86 end loop;
87 end if;
88
89 -- 1. Prepare message schedule
90
91 W (0 .. 15) := X;
92
93 for T in 16 .. Rounds - 1 loop
94 W (T) := S1 (W (T - 2)) + W (T - 7) + S0 (W (T - 15)) + W (T - 16);
95 end loop;
96
97 -- 2. Initialize working variables
98
99 A := H_St (0);
100 B := H_St (1);
101 C := H_St (2);
102 D := H_St (3);
103 E := H_St (4);
104 F := H_St (5);
105 G := H_St (6);
106 H := H_St (7);
107
108 -- 3. Perform transformation rounds
109
110 for T in 0 .. Rounds - 1 loop
111 T1 := H + Sigma1 (E) + Ch (E, F, G) + K (T) + W (T);
112 T2 := Sigma0 (A) + Maj (A, B, C);
113 H := G;
114 G := F;
115 F := E;
116 E := D + T1;
117 D := C;
118 C := B;
119 B := A;
120 A := T1 + T2;
121 end loop;
122
123 -- 4. Update hash state
124
125 H_St (0) := A + H_St (0);
126 H_St (1) := B + H_St (1);
127 H_St (2) := C + H_St (2);
128 H_St (3) := D + H_St (3);
129 H_St (4) := E + H_St (4);
130 H_St (5) := F + H_St (5);
131 H_St (6) := G + H_St (6);
132 H_St (7) := H + H_St (7);
133 end Transform;
134
135 end GNAT.Secure_Hashes.SHA2_Common;