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+/**
+ * \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion
+ *
+ * Copyright (C) 2006-2010, Brainspark B.V.
+ *
+ * This file is part of PolarSSL (http://www.polarssl.org)
+ * Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+/*
+ * The HAVEGE RNG was designed by Andre Seznec in 2002.
+ *
+ * http://www.irisa.fr/caps/projects/hipsor/publi.php
+ *
+ * Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
+ */
+
+#include "polarssl/config.h"
+
+#if defined(POLARSSL_HAVEGE_C)
+
+#include "polarssl/havege.h"
+#include "polarssl/timing.h"
+
+#include <string.h>
+#include <time.h>
+
+/* ------------------------------------------------------------------------
+ * On average, one iteration accesses two 8-word blocks in the havege WALK
+ * table, and generates 16 words in the RES array.
+ *
+ * The data read in the WALK table is updated and permuted after each use.
+ * The result of the hardware clock counter read is used for this update.
+ *
+ * 25 conditional tests are present. The conditional tests are grouped in
+ * two nested groups of 12 conditional tests and 1 test that controls the
+ * permutation; on average, there should be 6 tests executed and 3 of them
+ * should be mispredicted.
+ * ------------------------------------------------------------------------
+ */
+
+#define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
+
+#define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
+#define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
+
+#define TST1_LEAVE U1++; }
+#define TST2_LEAVE U2++; }
+
+#define ONE_ITERATION \
+ \
+ PTEST = PT1 >> 20; \
+ \
+ TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
+ TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
+ TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
+ \
+ TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
+ TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
+ TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
+ \
+ PTX = (PT1 >> 18) & 7; \
+ PT1 &= 0x1FFF; \
+ PT2 &= 0x1FFF; \
+ CLK = (int) hardclock(); \
+ \
+ i = 0; \
+ A = &WALK[PT1 ]; RES[i++] ^= *A; \
+ B = &WALK[PT2 ]; RES[i++] ^= *B; \
+ C = &WALK[PT1 ^ 1]; RES[i++] ^= *C; \
+ D = &WALK[PT2 ^ 4]; RES[i++] ^= *D; \
+ \
+ IN = (*A >> (1)) ^ (*A << (31)) ^ CLK; \
+ *A = (*B >> (2)) ^ (*B << (30)) ^ CLK; \
+ *B = IN ^ U1; \
+ *C = (*C >> (3)) ^ (*C << (29)) ^ CLK; \
+ *D = (*D >> (4)) ^ (*D << (28)) ^ CLK; \
+ \
+ A = &WALK[PT1 ^ 2]; RES[i++] ^= *A; \
+ B = &WALK[PT2 ^ 2]; RES[i++] ^= *B; \
+ C = &WALK[PT1 ^ 3]; RES[i++] ^= *C; \
+ D = &WALK[PT2 ^ 6]; RES[i++] ^= *D; \
+ \
+ if( PTEST & 1 ) SWAP( A, C ); \
+ \
+ IN = (*A >> (5)) ^ (*A << (27)) ^ CLK; \
+ *A = (*B >> (6)) ^ (*B << (26)) ^ CLK; \
+ *B = IN; CLK = (int) hardclock(); \
+ *C = (*C >> (7)) ^ (*C << (25)) ^ CLK; \
+ *D = (*D >> (8)) ^ (*D << (24)) ^ CLK; \
+ \
+ A = &WALK[PT1 ^ 4]; \
+ B = &WALK[PT2 ^ 1]; \
+ \
+ PTEST = PT2 >> 1; \
+ \
+ PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]); \
+ PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8); \
+ PTY = (PT2 >> 10) & 7; \
+ \
+ TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
+ TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
+ TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
+ \
+ TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
+ TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
+ TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
+ \
+ C = &WALK[PT1 ^ 5]; \
+ D = &WALK[PT2 ^ 5]; \
+ \
+ RES[i++] ^= *A; \
+ RES[i++] ^= *B; \
+ RES[i++] ^= *C; \
+ RES[i++] ^= *D; \
+ \
+ IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK; \
+ *A = (*B >> (10)) ^ (*B << (22)) ^ CLK; \
+ *B = IN ^ U2; \
+ *C = (*C >> (11)) ^ (*C << (21)) ^ CLK; \
+ *D = (*D >> (12)) ^ (*D << (20)) ^ CLK; \
+ \
+ A = &WALK[PT1 ^ 6]; RES[i++] ^= *A; \
+ B = &WALK[PT2 ^ 3]; RES[i++] ^= *B; \
+ C = &WALK[PT1 ^ 7]; RES[i++] ^= *C; \
+ D = &WALK[PT2 ^ 7]; RES[i++] ^= *D; \
+ \
+ IN = (*A >> (13)) ^ (*A << (19)) ^ CLK; \
+ *A = (*B >> (14)) ^ (*B << (18)) ^ CLK; \
+ *B = IN; \
+ *C = (*C >> (15)) ^ (*C << (17)) ^ CLK; \
+ *D = (*D >> (16)) ^ (*D << (16)) ^ CLK; \
+ \
+ PT1 = ( RES[(i - 8) ^ PTX] ^ \
+ WALK[PT1 ^ PTX ^ 7] ) & (~1); \
+ PT1 ^= (PT2 ^ 0x10) & 0x10; \
+ \
+ for( n++, i = 0; i < 16; i++ ) \
+ hs->pool[n % COLLECT_SIZE] ^= RES[i];
+
+/*
+ * Entropy gathering function
+ */
+static void havege_fill( havege_state *hs )
+{
+ int i, n = 0;
+ int U1, U2, *A, *B, *C, *D;
+ int PT1, PT2, *WALK, RES[16];
+ int PTX, PTY, CLK, PTEST, IN;
+
+ WALK = hs->WALK;
+ PT1 = hs->PT1;
+ PT2 = hs->PT2;
+
+ PTX = U1 = 0;
+ PTY = U2 = 0;
+
+ memset( RES, 0, sizeof( RES ) );
+
+ while( n < COLLECT_SIZE * 4 )
+ {
+ ONE_ITERATION
+ ONE_ITERATION
+ ONE_ITERATION
+ ONE_ITERATION
+ }
+
+ hs->PT1 = PT1;
+ hs->PT2 = PT2;
+
+ hs->offset[0] = 0;
+ hs->offset[1] = COLLECT_SIZE / 2;
+}
+
+/*
+ * HAVEGE initialization
+ */
+void havege_init( havege_state *hs )
+{
+ memset( hs, 0, sizeof( havege_state ) );
+
+ havege_fill( hs );
+}
+
+/*
+ * HAVEGE rand function
+ */
+int havege_random( void *p_rng, unsigned char *buf, size_t len )
+{
+ int val;
+ size_t use_len;
+ havege_state *hs = (havege_state *) p_rng;
+ unsigned char *p = buf;
+
+ while( len > 0 )
+ {
+ use_len = len;
+ if( use_len > sizeof(int) )
+ use_len = sizeof(int);
+
+ if( hs->offset[1] >= COLLECT_SIZE )
+ havege_fill( hs );
+
+ val = hs->pool[hs->offset[0]++];
+ val ^= hs->pool[hs->offset[1]++];
+
+ memcpy( p, &val, use_len );
+
+ len -= use_len;
+ p += use_len;
+ }
+
+ return( 0 );
+}
+
+#endif
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