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diff --git a/src/secp256k1/src/ecmult_gen_impl.h b/src/secp256k1/src/ecmult_gen_impl.h
new file mode 100644
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+++ b/src/secp256k1/src/ecmult_gen_impl.h
@@ -0,0 +1,118 @@
+/**********************************************************************
+ * 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_GEN_IMPL_H_
+#define _SECP256K1_ECMULT_GEN_IMPL_H_
+
+#include "scalar.h"
+#include "group.h"
+#include "ecmult_gen.h"
+
+typedef struct {
+    /* For accelerating the computation of a*G:
+     * To harden against timing attacks, use the following mechanism:
+     * * Break up the multiplicand into groups of 4 bits, called n_0, n_1, n_2, ..., n_63.
+     * * Compute sum(n_i * 16^i * G + U_i, i=0..63), where:
+     *   * U_i = U * 2^i (for i=0..62)
+     *   * U_i = U * (1-2^63) (for i=63)
+     *   where U is a point with no known corresponding scalar. Note that sum(U_i, i=0..63) = 0.
+     * For each i, and each of the 16 possible values of n_i, (n_i * 16^i * G + U_i) is
+     * precomputed (call it prec(i, n_i)). The formula now becomes sum(prec(i, n_i), i=0..63).
+     * None of the resulting prec group elements have a known scalar, and neither do any of
+     * the intermediate sums while computing a*G.
+     * To make memory access uniform, the bytes of prec(i, n_i) are sliced per value of n_i. */
+    unsigned char prec[64][sizeof(secp256k1_ge_t)][16]; /* prec[j][k][i] = k'th byte of (16^j * i * G + U_i) */
+} secp256k1_ecmult_gen_consts_t;
+
+static const secp256k1_ecmult_gen_consts_t *secp256k1_ecmult_gen_consts = NULL;
+
+static void secp256k1_ecmult_gen_start(void) {
+    if (secp256k1_ecmult_gen_consts != NULL)
+        return;
+
+    /* Allocate the precomputation table. */
+    secp256k1_ecmult_gen_consts_t *ret = (secp256k1_ecmult_gen_consts_t*)malloc(sizeof(secp256k1_ecmult_gen_consts_t));
+
+    /* get the generator */
+    const secp256k1_ge_t *g = &secp256k1_ge_consts->g;
+    secp256k1_gej_t gj; secp256k1_gej_set_ge(&gj, g);
+
+    /* Construct a group element with no known corresponding scalar (nothing up my sleeve). */
+    secp256k1_gej_t nums_gej;
+    {
+        static const unsigned char nums_b32[32] = "The scalar for this x is unknown";
+        secp256k1_fe_t nums_x;
+        secp256k1_fe_set_b32(&nums_x, nums_b32);
+        secp256k1_ge_t nums_ge;
+        VERIFY_CHECK(secp256k1_ge_set_xo(&nums_ge, &nums_x, 0));
+        secp256k1_gej_set_ge(&nums_gej, &nums_ge);
+        /* Add G to make the bits in x uniformly distributed. */
+        secp256k1_gej_add_ge_var(&nums_gej, &nums_gej, g);
+    }
+
+    /* compute prec. */
+    secp256k1_ge_t prec[1024];
+    {
+        secp256k1_gej_t precj[1024]; /* Jacobian versions of prec. */
+        secp256k1_gej_t gbase; gbase = gj; /* 16^j * G */
+        secp256k1_gej_t numsbase; numsbase = nums_gej; /* 2^j * nums. */
+        for (int j=0; j<64; j++) {
+            /* Set precj[j*16 .. j*16+15] to (numsbase, numsbase + gbase, ..., numsbase + 15*gbase). */
+            precj[j*16] = numsbase;
+            for (int i=1; i<16; i++) {
+                secp256k1_gej_add_var(&precj[j*16 + i], &precj[j*16 + i - 1], &gbase);
+            }
+            /* Multiply gbase by 16. */
+            for (int i=0; i<4; i++) {
+                secp256k1_gej_double_var(&gbase, &gbase);
+            }
+            /* Multiply numbase by 2. */
+            secp256k1_gej_double_var(&numsbase, &numsbase);
+            if (j == 62) {
+                /* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
+                secp256k1_gej_neg(&numsbase, &numsbase);
+                secp256k1_gej_add_var(&numsbase, &numsbase, &nums_gej);
+            }
+        }
+        secp256k1_ge_set_all_gej_var(1024, prec, precj);
+    }
+    for (int j=0; j<64; j++) {
+        for (int i=0; i<16; i++) {
+            const unsigned char* raw = (const unsigned char*)(&prec[j*16 + i]);
+            for (size_t k=0; k<sizeof(secp256k1_ge_t); k++)
+                ret->prec[j][k][i] = raw[k];
+        }
+    }
+
+    /* Set the global pointer to the precomputation table. */
+    secp256k1_ecmult_gen_consts = ret;
+}
+
+static void secp256k1_ecmult_gen_stop(void) {
+    if (secp256k1_ecmult_gen_consts == NULL)
+        return;
+
+    secp256k1_ecmult_gen_consts_t *c = (secp256k1_ecmult_gen_consts_t*)secp256k1_ecmult_gen_consts;
+    secp256k1_ecmult_gen_consts = NULL;
+    free(c);
+}
+
+static void secp256k1_ecmult_gen(secp256k1_gej_t *r, const secp256k1_scalar_t *gn) {
+    const secp256k1_ecmult_gen_consts_t *c = secp256k1_ecmult_gen_consts;
+    secp256k1_gej_set_infinity(r);
+    secp256k1_ge_t add;
+    int bits;
+    for (int j=0; j<64; j++) {
+        bits = secp256k1_scalar_get_bits(gn, j * 4, 4);
+        for (size_t k=0; k<sizeof(secp256k1_ge_t); k++)
+            ((unsigned char*)(&add))[k] = c->prec[j][k][bits];
+        secp256k1_gej_add_ge(r, r, &add);
+    }
+    bits = 0;
+    secp256k1_ge_clear(&add);
+}
+
+#endif