diff --git a/include/cryb/mpi.h b/include/cryb/mpi.h
index de147ff..d45d3fd 100644
--- a/include/cryb/mpi.h
+++ b/include/cryb/mpi.h
@@ -65,6 +65,8 @@ const char *cryb_mpi_version(void);
#define mpi_lsb cryb_mpi_lsb
#define mpi_lshift cryb_mpi_lshift
#define mpi_msb cryb_mpi_msb
+#define mpi_mul cryb_mpi_mul
+#define mpi_mul_abs cryb_mpi_mul_abs
#define mpi_negate cryb_mpi_negate
#define mpi_rshift cryb_mpi_rshift
#define mpi_set cryb_mpi_set
@@ -113,6 +115,8 @@ int mpi_load(cryb_mpi *, const uint8_t *, size_t);
unsigned int mpi_lsb(const cryb_mpi *);
int mpi_lshift(cryb_mpi *, unsigned int);
unsigned int mpi_msb(const cryb_mpi *);
+int mpi_mul(cryb_mpi *, const cryb_mpi *, const cryb_mpi *);
+int mpi_mul_abs(cryb_mpi *, const cryb_mpi *, const cryb_mpi *);
void mpi_negate(cryb_mpi *);
int mpi_rshift(cryb_mpi *, unsigned int);
int mpi_set(cryb_mpi *, int32_t);
diff --git a/lib/mpi/Makefile.am b/lib/mpi/Makefile.am
index 0458d7a..df4c455 100644
--- a/lib/mpi/Makefile.am
+++ b/lib/mpi/Makefile.am
@@ -22,6 +22,8 @@ libcryb_mpi_la_SOURCES = \
cryb_mpi_lsb.c \
cryb_mpi_lshift.c \
cryb_mpi_msb.c \
+ cryb_mpi_mul.c \
+ cryb_mpi_mul_abs.c \
cryb_mpi_negate.c \
cryb_mpi_rshift.c \
cryb_mpi_set.c \
diff --git a/lib/mpi/cryb_mpi_mul.c b/lib/mpi/cryb_mpi_mul.c
new file mode 100644
index 0000000..b0363e2
--- /dev/null
+++ b/lib/mpi/cryb_mpi_mul.c
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2017 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ * products derived from this software without specific prior written
+ * permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <cryb/mpi.h>
+
+#include "cryb_mpi_impl.h"
+
+/*
+ * Store the product of A and B in X.
+ */
+int
+mpi_mul(cryb_mpi *X, const cryb_mpi *A, const cryb_mpi *B)
+{
+ int neg;
+
+ neg = A->neg ^ B->neg;
+ if (mpi_mul_abs(X, A, B) < 0)
+ return (-1);
+ if (X->msb > 0)
+ X->neg = neg;
+ return (0);
+}
+
diff --git a/lib/mpi/cryb_mpi_mul_abs.c b/lib/mpi/cryb_mpi_mul_abs.c
new file mode 100644
index 0000000..37f5ad6
--- /dev/null
+++ b/lib/mpi/cryb_mpi_mul_abs.c
@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2017 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ * products derived from this software without specific prior written
+ * permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <strings.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/mpi.h>
+
+#include "cryb_mpi_impl.h"
+
+/*
+ * Store the product of the absolutes values of A and B in X.
+ *
+ * Note: this is loosely based on HAC 14.2.3. However, the first
+ * paragraph speaks of x and y having n and t digits respectively, with
+ * the most significant digits being x[n - 1] and y[t - 1], but the rest
+ * of the section refers to x and y having n + 1 and t + 1 digits. We
+ * follow the former convention, but use a and b instead of n and t to
+ * distance ourselves from this confusing text.
+ */
+int
+mpi_mul_abs(cryb_mpi *X, const cryb_mpi *A, const cryb_mpi *B)
+{
+ cryb_mpi *P, T = CRYB_MPI_ZERO;
+ uint64_t p;
+ unsigned int a, b, i, j;
+ uint32_t c;
+
+ /*
+ * Trivial cases: A and / or B is zero.
+ */
+ if (A->msb == 0 || B->msb == 0) {
+ mpi_zero(X);
+ return (0);
+ }
+
+ /*
+ * Unlike addition or subtraction, we can't multiply in place, so
+ * if the destination is identical with one of the operands, we
+ * will have to use temporary storage. Either way, make sure we
+ * have enough room for the product.
+ */
+ P = (X == A || X == B) ? &T : X;
+ mpi_zero(P);
+ a = (A->msb + 31) / 32;
+ b = (B->msb + 31) / 32;
+ if (mpi_grow(P, (a + b) * 32) != 0)
+ return (-1);
+
+ /*
+ * Multiply...
+ */
+ for (i = 0; i < b; ++i) {
+ for (c = j = 0; j < a; ++j) {
+ p = 1ULL * A->words[j] * B->words[i] + c;
+ P->words[i + j] += p & 0xffffffffUL;
+ c = p >> 32;
+ }
+ P->words[i + j] = c;
+ }
+ if (P->words[i = a + b - 1] == 0)
+ --i;
+ P->msb = i * 32 + flsl(P->words[i]);
+
+ /*
+ * If we used temporary storage, copy back and clean up.
+ */
+ if (P == &T) {
+ cryb_mpi_swap(X, P);
+ cryb_mpi_destroy(P);
+ }
+
+ return (0);
+}
diff --git a/t/t_mpi_muldiv.c b/t/t_mpi_muldiv.c
index e4c6be9..dcbad57 100644
--- a/t/t_mpi_muldiv.c
+++ b/t/t_mpi_muldiv.c
@@ -59,12 +59,54 @@ static struct t_mul_case {
size_t emsb;
int eneg:1;
} t_mul_cases[] = {
+ {
+ "0 * 0 == 0",
+ { }, 0, 0,
+ { }, 0, 0,
+ { }, 0, 0,
+ },
+ {
+ "0 * 1 == 0",
+ { }, 0, 0,
+ { 0x01 }, 1, 0,
+ { }, 0, 0,
+ },
+ {
+ "1 * 0 == 0",
+ { 0x01 }, 1, 0,
+ { }, 0, 0,
+ { }, 0, 0,
+ },
{
"1 * 1 == 1",
{ 0x01 }, 1, 0,
{ 0x01 }, 1, 0,
{ 0x01 }, 1, 0,
},
+ {
+ "(2^32 + 1) * (2^32 + 1) == 2^64 + 2^33 + 1",
+ { 0x01, 0x00, 0x00, 0x00, 0x01 }, 33, 0,
+ { 0x01, 0x00, 0x00, 0x00, 0x01 }, 33, 0,
+ { 0x01, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x01 }, 65, 0,
+ },
+ {
+ "(2^32 + 1) * (2^32 - 1) == 2^64 - 1",
+ { 0x01, 0x00, 0x00, 0x00, 0x01 }, 33, 0,
+ { 0xff, 0xff, 0xff, 0xff }, 32, 0,
+ { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }, 63, 0,
+ },
+ {
+ "(2^32 - 1) * (2^32 + 1) == 2^64 - 1",
+ { 0xff, 0xff, 0xff, 0xff }, 32, 0,
+ { 0x01, 0x00, 0x00, 0x00, 0x01 }, 33, 0,
+ { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }, 63, 0,
+ },
+ {
+ "(2^32 - 1) * (2^32 - 1) == 2^64 - 2^33 + 1",
+ { 0xff, 0xff, 0xff, 0xff }, 32, 0,
+ { 0xff, 0xff, 0xff, 0xff }, 32, 0,
+ { 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x00, 0x01 }, 64, 0,
+ },
};
static int
@@ -81,11 +123,7 @@ t_mpi_mul_tc(char **desc CRYB_UNUSED, void *arg)
b.neg = tc->bneg;
mpi_load(&e, tc->e, (tc->emsb + 7) / 8);
e.neg = tc->eneg;
-#if 0
ret &= t_compare_i(0, mpi_mul_abs(&x, &a, &b));
-#else
- mpi_load(&x, tc->e, (tc->emsb + 7) / 8);
-#endif
ret &= t_compare_mpi(&e, &x);
mpi_destroy(&a);
mpi_destroy(&b);