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diff --git a/src/secp256k1/src/ecmult_impl.h b/src/secp256k1/src/ecmult_impl.h
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+/**********************************************************************
+ * Copyright (c) 2013, 2014 Pieter Wuille                             *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _SECP256K1_ECMULT_IMPL_H_
+#define _SECP256K1_ECMULT_IMPL_H_
+
+#include "num.h"
+#include "group.h"
+#include "ecmult.h"
+
+/* optimal for 128-bit and 256-bit exponents. */
+#define WINDOW_A 5
+
+/** larger numbers may result in slightly better performance, at the cost of
+    exponentially larger precomputed tables. WINDOW_G == 14 results in 640 KiB. */
+#define WINDOW_G 14
+
+/** Fill a table 'pre' with precomputed odd multiples of a. W determines the size of the table.
+ *  pre will contains the values [1*a,3*a,5*a,...,(2^(w-1)-1)*a], so it needs place for
+ *  2^(w-2) entries.
+ *
+ *  There are two versions of this function:
+ *  - secp256k1_ecmult_precomp_wnaf_gej, which operates on group elements in jacobian notation,
+ *    fast to precompute, but slower to use in later additions.
+ *  - secp256k1_ecmult_precomp_wnaf_ge, which operates on group elements in affine notations,
+ *    (much) slower to precompute, but a bit faster to use in later additions.
+ *  To compute a*P + b*G, we use the jacobian version for P, and the affine version for G, as
+ *  G is constant, so it only needs to be done once in advance.
+ */
+static void secp256k1_ecmult_table_precomp_gej_var(secp256k1_gej_t *pre, const secp256k1_gej_t *a, int w) {
+    pre[0] = *a;
+    secp256k1_gej_t d; secp256k1_gej_double_var(&d, &pre[0]);
+    for (int i=1; i<(1 << (w-2)); i++)
+        secp256k1_gej_add_var(&pre[i], &d, &pre[i-1]);
+}
+
+static void secp256k1_ecmult_table_precomp_ge_var(secp256k1_ge_t *pre, const secp256k1_gej_t *a, int w) {
+    const int table_size = 1 << (w-2);
+    secp256k1_gej_t prej[table_size];
+    prej[0] = *a;
+    secp256k1_gej_t d; secp256k1_gej_double_var(&d, a);
+    for (int i=1; i<table_size; i++) {
+        secp256k1_gej_add_var(&prej[i], &d, &prej[i-1]);
+    }
+    secp256k1_ge_set_all_gej_var(table_size, pre, prej);
+}
+
+/** The number of entries a table with precomputed multiples needs to have. */
+#define ECMULT_TABLE_SIZE(w) (1 << ((w)-2))
+
+/** The following two macro retrieves a particular odd multiple from a table
+ *  of precomputed multiples. */
+#define ECMULT_TABLE_GET(r,pre,n,w,neg) do { \
+    VERIFY_CHECK(((n) & 1) == 1); \
+    VERIFY_CHECK((n) >= -((1 << ((w)-1)) - 1)); \
+    VERIFY_CHECK((n) <=  ((1 << ((w)-1)) - 1)); \
+    if ((n) > 0) \
+        *(r) = (pre)[((n)-1)/2]; \
+    else \
+        (neg)((r), &(pre)[(-(n)-1)/2]); \
+} while(0)
+
+#define ECMULT_TABLE_GET_GEJ(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_gej_neg)
+#define ECMULT_TABLE_GET_GE(r,pre,n,w)  ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_ge_neg)
+
+typedef struct {
+    /* For accelerating the computation of a*P + b*G: */
+    secp256k1_ge_t pre_g[ECMULT_TABLE_SIZE(WINDOW_G)];    /* odd multiples of the generator */
+    secp256k1_ge_t pre_g_128[ECMULT_TABLE_SIZE(WINDOW_G)]; /* odd multiples of 2^128*generator */
+} secp256k1_ecmult_consts_t;
+
+static const secp256k1_ecmult_consts_t *secp256k1_ecmult_consts = NULL;
+
+static void secp256k1_ecmult_start(void) {
+    if (secp256k1_ecmult_consts != NULL)
+        return;
+
+    /* Allocate the precomputation table. */
+    secp256k1_ecmult_consts_t *ret = (secp256k1_ecmult_consts_t*)malloc(sizeof(secp256k1_ecmult_consts_t));
+
+    /* get the generator */
+    const secp256k1_ge_t *g = &secp256k1_ge_consts->g;
+    secp256k1_gej_t gj; secp256k1_gej_set_ge(&gj, g);
+
+    /* calculate 2^128*generator */
+    secp256k1_gej_t g_128j = gj;
+    for (int i=0; i<128; i++)
+        secp256k1_gej_double_var(&g_128j, &g_128j);
+
+    /* precompute the tables with odd multiples */
+    secp256k1_ecmult_table_precomp_ge_var(ret->pre_g, &gj, WINDOW_G);
+    secp256k1_ecmult_table_precomp_ge_var(ret->pre_g_128, &g_128j, WINDOW_G);
+
+    /* Set the global pointer to the precomputation table. */
+    secp256k1_ecmult_consts = ret;
+}
+
+static void secp256k1_ecmult_stop(void) {
+    if (secp256k1_ecmult_consts == NULL)
+        return;
+
+    secp256k1_ecmult_consts_t *c = (secp256k1_ecmult_consts_t*)secp256k1_ecmult_consts;
+    secp256k1_ecmult_consts = NULL;
+    free(c);
+}
+
+/** Convert a number to WNAF notation. The number becomes represented by sum(2^i * wnaf[i], i=0..bits),
+ *  with the following guarantees:
+ *  - each wnaf[i] is either 0, or an odd integer between -(1<<(w-1) - 1) and (1<<(w-1) - 1)
+ *  - two non-zero entries in wnaf are separated by at least w-1 zeroes.
+ *  - the index of the highest non-zero entry in wnaf (=return value-1) is at most bits, where
+ *    bits is the number of bits necessary to represent the absolute value of the input.
+ */
+static int secp256k1_ecmult_wnaf(int *wnaf, const secp256k1_num_t *a, int w) {
+    int ret = 0;
+    int zeroes = 0;
+    secp256k1_num_t x;
+    secp256k1_num_copy(&x, a);
+    int sign = 1;
+    if (secp256k1_num_is_neg(&x)) {
+        sign = -1;
+        secp256k1_num_negate(&x);
+    }
+    while (!secp256k1_num_is_zero(&x)) {
+        while (!secp256k1_num_is_odd(&x)) {
+            zeroes++;
+            secp256k1_num_shift(&x, 1);
+        }
+        int word = secp256k1_num_shift(&x, w);
+        while (zeroes) {
+            wnaf[ret++] = 0;
+            zeroes--;
+        }
+        if (word & (1 << (w-1))) {
+            secp256k1_num_inc(&x);
+            wnaf[ret++] = sign * (word - (1 << w));
+        } else {
+            wnaf[ret++] = sign * word;
+        }
+        zeroes = w-1;
+    }
+    return ret;
+}
+
+static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const secp256k1_num_t *na, const secp256k1_num_t *ng) {
+    const secp256k1_ecmult_consts_t *c = secp256k1_ecmult_consts;
+
+#ifdef USE_ENDOMORPHISM
+    secp256k1_num_t na_1, na_lam;
+    /* split na into na_1 and na_lam (where na = na_1 + na_lam*lambda, and na_1 and na_lam are ~128 bit) */
+    secp256k1_gej_split_exp_var(&na_1, &na_lam, na);
+
+    /* build wnaf representation for na_1 and na_lam. */
+    int wnaf_na_1[129];   int bits_na_1   = secp256k1_ecmult_wnaf(wnaf_na_1,   &na_1,   WINDOW_A);
+    int wnaf_na_lam[129]; int bits_na_lam = secp256k1_ecmult_wnaf(wnaf_na_lam, &na_lam, WINDOW_A);
+    int bits = bits_na_1;
+    if (bits_na_lam > bits) bits = bits_na_lam;
+#else
+    /* build wnaf representation for na. */
+    int wnaf_na[257];     int bits_na     = secp256k1_ecmult_wnaf(wnaf_na,     na,      WINDOW_A);
+    int bits = bits_na;
+#endif
+
+    /* calculate odd multiples of a */
+    secp256k1_gej_t pre_a[ECMULT_TABLE_SIZE(WINDOW_A)];
+    secp256k1_ecmult_table_precomp_gej_var(pre_a, a, WINDOW_A);
+
+#ifdef USE_ENDOMORPHISM
+    secp256k1_gej_t pre_a_lam[ECMULT_TABLE_SIZE(WINDOW_A)];
+    for (int i=0; i<ECMULT_TABLE_SIZE(WINDOW_A); i++)
+        secp256k1_gej_mul_lambda(&pre_a_lam[i], &pre_a[i]);
+#endif
+
+    /* Splitted G factors. */
+    secp256k1_num_t ng_1, ng_128;
+
+    /* split ng into ng_1 and ng_128 (where gn = gn_1 + gn_128*2^128, and gn_1 and gn_128 are ~128 bit) */
+    secp256k1_num_split(&ng_1, &ng_128, ng, 128);
+
+    /* Build wnaf representation for ng_1 and ng_128 */
+    int wnaf_ng_1[129];   int bits_ng_1   = secp256k1_ecmult_wnaf(wnaf_ng_1,   &ng_1,   WINDOW_G);
+    int wnaf_ng_128[129]; int bits_ng_128 = secp256k1_ecmult_wnaf(wnaf_ng_128, &ng_128, WINDOW_G);
+    if (bits_ng_1 > bits) bits = bits_ng_1;
+    if (bits_ng_128 > bits) bits = bits_ng_128;
+
+    secp256k1_gej_set_infinity(r);
+    secp256k1_gej_t tmpj;
+    secp256k1_ge_t tmpa;
+
+    for (int i=bits-1; i>=0; i--) {
+        secp256k1_gej_double_var(r, r);
+        int n;
+#ifdef USE_ENDOMORPHISM
+        if (i < bits_na_1 && (n = wnaf_na_1[i])) {
+            ECMULT_TABLE_GET_GEJ(&tmpj, pre_a, n, WINDOW_A);
+            secp256k1_gej_add_var(r, r, &tmpj);
+        }
+        if (i < bits_na_lam && (n = wnaf_na_lam[i])) {
+            ECMULT_TABLE_GET_GEJ(&tmpj, pre_a_lam, n, WINDOW_A);
+            secp256k1_gej_add_var(r, r, &tmpj);
+        }
+#else
+        if (i < bits_na && (n = wnaf_na[i])) {
+            ECMULT_TABLE_GET_GEJ(&tmpj, pre_a, n, WINDOW_A);
+            secp256k1_gej_add_var(r, r, &tmpj);
+        }
+#endif
+        if (i < bits_ng_1 && (n = wnaf_ng_1[i])) {
+            ECMULT_TABLE_GET_GE(&tmpa, c->pre_g, n, WINDOW_G);
+            secp256k1_gej_add_ge_var(r, r, &tmpa);
+        }
+        if (i < bits_ng_128 && (n = wnaf_ng_128[i])) {
+            ECMULT_TABLE_GET_GE(&tmpa, c->pre_g_128, n, WINDOW_G);
+            secp256k1_gej_add_ge_var(r, r, &tmpa);
+        }
+    }
+}
+
+#endif