havege.c

00001 /**
00002  *  \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion
00003  *
00004  *  Copyright (C) 2006-2014, Brainspark B.V.
00005  *
00006  *  This file is part of PolarSSL (http://www.polarssl.org)
00007  *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
00008  *
00009  *  All rights reserved.
00010  *
00011  *  This program is free software; you can redistribute it and/or modify
00012  *  it under the terms of the GNU General Public License as published by
00013  *  the Free Software Foundation; either version 2 of the License, or
00014  *  (at your option) any later version.
00015  *
00016  *  This program is distributed in the hope that it will be useful,
00017  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  *  GNU General Public License for more details.
00020  *
00021  *  You should have received a copy of the GNU General Public License along
00022  *  with this program; if not, write to the Free Software Foundation, Inc.,
00023  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
00024  */
00025 /*
00026  *  The HAVEGE RNG was designed by Andre Seznec in 2002.
00027  *
00028  *  http://www.irisa.fr/caps/projects/hipsor/publi.php
00029  *
00030  *  Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
00031  */
00032 
00033 #if !defined(POLARSSL_CONFIG_FILE)
00034 #include "polarssl/config.h"
00035 #else
00036 #include POLARSSL_CONFIG_FILE
00037 #endif
00038 
00039 #if defined(POLARSSL_HAVEGE_C)
00040 
00041 #include "polarssl/havege.h"
00042 #include "polarssl/timing.h"
00043 
00044 #include <string.h>
00045 
00046 /* ------------------------------------------------------------------------
00047  * On average, one iteration accesses two 8-word blocks in the havege WALK
00048  * table, and generates 16 words in the RES array.
00049  *
00050  * The data read in the WALK table is updated and permuted after each use.
00051  * The result of the hardware clock counter read is used  for this update.
00052  *
00053  * 25 conditional tests are present.  The conditional tests are grouped in
00054  * two nested  groups of 12 conditional tests and 1 test that controls the
00055  * permutation; on average, there should be 6 tests executed and 3 of them
00056  * should be mispredicted.
00057  * ------------------------------------------------------------------------
00058  */
00059 
00060 #define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
00061 
00062 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
00063 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
00064 
00065 #define TST1_LEAVE U1++; }
00066 #define TST2_LEAVE U2++; }
00067 
00068 #define ONE_ITERATION                                   \
00069                                                         \
00070     PTEST = PT1 >> 20;                                  \
00071                                                         \
00072     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00073     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00074     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00075                                                         \
00076     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00077     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00078     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00079                                                         \
00080     PTX = (PT1 >> 18) & 7;                              \
00081     PT1 &= 0x1FFF;                                      \
00082     PT2 &= 0x1FFF;                                      \
00083     CLK = (int) hardclock();                            \
00084                                                         \
00085     i = 0;                                              \
00086     A = &WALK[PT1    ]; RES[i++] ^= *A;                 \
00087     B = &WALK[PT2    ]; RES[i++] ^= *B;                 \
00088     C = &WALK[PT1 ^ 1]; RES[i++] ^= *C;                 \
00089     D = &WALK[PT2 ^ 4]; RES[i++] ^= *D;                 \
00090                                                         \
00091     IN = (*A >> (1)) ^ (*A << (31)) ^ CLK;              \
00092     *A = (*B >> (2)) ^ (*B << (30)) ^ CLK;              \
00093     *B = IN ^ U1;                                       \
00094     *C = (*C >> (3)) ^ (*C << (29)) ^ CLK;              \
00095     *D = (*D >> (4)) ^ (*D << (28)) ^ CLK;              \
00096                                                         \
00097     A = &WALK[PT1 ^ 2]; RES[i++] ^= *A;                 \
00098     B = &WALK[PT2 ^ 2]; RES[i++] ^= *B;                 \
00099     C = &WALK[PT1 ^ 3]; RES[i++] ^= *C;                 \
00100     D = &WALK[PT2 ^ 6]; RES[i++] ^= *D;                 \
00101                                                         \
00102     if( PTEST & 1 ) SWAP( A, C );                       \
00103                                                         \
00104     IN = (*A >> (5)) ^ (*A << (27)) ^ CLK;              \
00105     *A = (*B >> (6)) ^ (*B << (26)) ^ CLK;              \
00106     *B = IN; CLK = (int) hardclock();                   \
00107     *C = (*C >> (7)) ^ (*C << (25)) ^ CLK;              \
00108     *D = (*D >> (8)) ^ (*D << (24)) ^ CLK;              \
00109                                                         \
00110     A = &WALK[PT1 ^ 4];                                 \
00111     B = &WALK[PT2 ^ 1];                                 \
00112                                                         \
00113     PTEST = PT2 >> 1;                                   \
00114                                                         \
00115     PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]);   \
00116     PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8);  \
00117     PTY = (PT2 >> 10) & 7;                              \
00118                                                         \
00119     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00120     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00121     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00122                                                         \
00123     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00124     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00125     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00126                                                         \
00127     C = &WALK[PT1 ^ 5];                                 \
00128     D = &WALK[PT2 ^ 5];                                 \
00129                                                         \
00130     RES[i++] ^= *A;                                     \
00131     RES[i++] ^= *B;                                     \
00132     RES[i++] ^= *C;                                     \
00133     RES[i++] ^= *D;                                     \
00134                                                         \
00135     IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK;             \
00136     *A = (*B >> (10)) ^ (*B << (22)) ^ CLK;             \
00137     *B = IN ^ U2;                                       \
00138     *C = (*C >> (11)) ^ (*C << (21)) ^ CLK;             \
00139     *D = (*D >> (12)) ^ (*D << (20)) ^ CLK;             \
00140                                                         \
00141     A = &WALK[PT1 ^ 6]; RES[i++] ^= *A;                 \
00142     B = &WALK[PT2 ^ 3]; RES[i++] ^= *B;                 \
00143     C = &WALK[PT1 ^ 7]; RES[i++] ^= *C;                 \
00144     D = &WALK[PT2 ^ 7]; RES[i++] ^= *D;                 \
00145                                                         \
00146     IN = (*A >> (13)) ^ (*A << (19)) ^ CLK;             \
00147     *A = (*B >> (14)) ^ (*B << (18)) ^ CLK;             \
00148     *B = IN;                                            \
00149     *C = (*C >> (15)) ^ (*C << (17)) ^ CLK;             \
00150     *D = (*D >> (16)) ^ (*D << (16)) ^ CLK;             \
00151                                                         \
00152     PT1 = ( RES[(i - 8) ^ PTX] ^                        \
00153             WALK[PT1 ^ PTX ^ 7] ) & (~1);               \
00154     PT1 ^= (PT2 ^ 0x10) & 0x10;                         \
00155                                                         \
00156     for( n++, i = 0; i < 16; i++ )                      \
00157         hs->pool[n % COLLECT_SIZE] ^= RES[i];
00158 
00159 /*
00160  * Entropy gathering function
00161  */
00162 static void havege_fill( havege_state *hs )
00163 {
00164     int i, n = 0;
00165     int  U1,  U2, *A, *B, *C, *D;
00166     int PT1, PT2, *WALK, RES[16];
00167     int PTX, PTY, CLK, PTEST, IN;
00168 
00169     WALK = hs->WALK;
00170     PT1  = hs->PT1;
00171     PT2  = hs->PT2;
00172 
00173     PTX  = U1 = 0;
00174     PTY  = U2 = 0;
00175 
00176     memset( RES, 0, sizeof( RES ) );
00177 
00178     while( n < COLLECT_SIZE * 4 )
00179     {
00180         ONE_ITERATION
00181         ONE_ITERATION
00182         ONE_ITERATION
00183         ONE_ITERATION
00184     }
00185 
00186     hs->PT1 = PT1;
00187     hs->PT2 = PT2;
00188 
00189     hs->offset[0] = 0;
00190     hs->offset[1] = COLLECT_SIZE / 2;
00191 }
00192 
00193 /*
00194  * HAVEGE initialization
00195  */
00196 void havege_init( havege_state *hs )
00197 {
00198     memset( hs, 0, sizeof( havege_state ) );
00199 
00200     havege_fill( hs );
00201 }
00202 
00203 /*
00204  * HAVEGE rand function
00205  */
00206 int havege_random( void *p_rng, unsigned char *buf, size_t len )
00207 {
00208     int val;
00209     size_t use_len;
00210     havege_state *hs = (havege_state *) p_rng;
00211     unsigned char *p = buf;
00212 
00213     while( len > 0 )
00214     {
00215         use_len = len;
00216         if( use_len > sizeof(int) )
00217             use_len = sizeof(int);
00218 
00219         if( hs->offset[1] >= COLLECT_SIZE )
00220             havege_fill( hs );
00221 
00222         val  = hs->pool[hs->offset[0]++];
00223         val ^= hs->pool[hs->offset[1]++];
00224 
00225         memcpy( p, &val, use_len );
00226 
00227         len -= use_len;
00228         p += use_len;
00229     }
00230 
00231     return( 0 );
00232 }
00233 
00234 #endif /* POLARSSL_HAVEGE_C */
00235 
00236