1 files changed, 390 insertions, 0 deletions
diff --git a/test/monniaux/BearSSL/src/ec/ec_c25519_i31.c b/test/monniaux/BearSSL/src/ec/ec_c25519_i31.c
new file mode 100644
index 00000000..f8ffc2c2
--- /dev/null
+++ b/test/monniaux/BearSSL/src/ec/ec_c25519_i31.c
@@ -0,0 +1,390 @@
+/*
+ * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/*
+ * Parameters for the field:
+ *   - field modulus p = 2^255-19
+ *   - R^2 mod p (R = 2^(31k) for the smallest k such that R >= p)
+ */
+
+static const uint32_t C255_P[] = {
+	0x00000107,
+	0x7FFFFFED, 0x7FFFFFFF, 0x7FFFFFFF, 0x7FFFFFFF, 0x7FFFFFFF,
+	0x7FFFFFFF, 0x7FFFFFFF, 0x7FFFFFFF, 0x0000007F
+};
+
+#define P0I   0x286BCA1B
+
+static const uint32_t C255_R2[] = {
+	0x00000107,
+	0x00000000, 0x02D20000, 0x00000000, 0x00000000, 0x00000000,
+	0x00000000, 0x00000000, 0x00000000, 0x00000000
+};
+
+static const uint32_t C255_A24[] = {
+	0x00000107,
+	0x53000000, 0x0000468B, 0x00000000, 0x00000000, 0x00000000,
+	0x00000000, 0x00000000, 0x00000000, 0x00000000
+};
+
+/* obsolete
+#include <stdio.h>
+#include <stdlib.h>
+static void
+print_int_mont(const char *name, const uint32_t *x)
+{
+	uint32_t y[10];
+	unsigned char tmp[32];
+	size_t u;
+
+	printf("%s = ", name);
+	memcpy(y, x, sizeof y);
+	br_i31_from_monty(y, C255_P, P0I);
+	br_i31_encode(tmp, sizeof tmp, y);
+	for (u = 0; u < sizeof tmp; u ++) {
+		printf("%02X", tmp[u]);
+	}
+	printf("\n");
+}
+*/
+
+static const unsigned char GEN[] = {
+	0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+static const unsigned char ORDER[] = {
+	0x7F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
+};
+
+static const unsigned char *
+api_generator(int curve, size_t *len)
+{
+	(void)curve;
+	*len = 32;
+	return GEN;
+}
+
+static const unsigned char *
+api_order(int curve, size_t *len)
+{
+	(void)curve;
+	*len = 32;
+	return ORDER;
+}
+
+static size_t
+api_xoff(int curve, size_t *len)
+{
+	(void)curve;
+	*len = 32;
+	return 0;
+}
+
+static void
+cswap(uint32_t *a, uint32_t *b, uint32_t ctl)
+{
+	int i;
+
+	ctl = -ctl;
+	for (i = 0; i < 10; i ++) {
+		uint32_t aw, bw, tw;
+
+		aw = a[i];
+		bw = b[i];
+		tw = ctl & (aw ^ bw);
+		a[i] = aw ^ tw;
+		b[i] = bw ^ tw;
+	}
+}
+
+static void
+c255_add(uint32_t *d, const uint32_t *a, const uint32_t *b)
+{
+	uint32_t ctl;
+	uint32_t t[10];
+
+	memcpy(t, a, sizeof t);
+	ctl = br_i31_add(t, b, 1);
+	ctl |= NOT(br_i31_sub(t, C255_P, 0));
+	br_i31_sub(t, C255_P, ctl);
+	memcpy(d, t, sizeof t);
+}
+
+static void
+c255_sub(uint32_t *d, const uint32_t *a, const uint32_t *b)
+{
+	uint32_t t[10];
+
+	memcpy(t, a, sizeof t);
+	br_i31_add(t, C255_P, br_i31_sub(t, b, 1));
+	memcpy(d, t, sizeof t);
+}
+
+static void
+c255_mul(uint32_t *d, const uint32_t *a, const uint32_t *b)
+{
+	uint32_t t[10];
+
+	br_i31_montymul(t, a, b, C255_P, P0I);
+	memcpy(d, t, sizeof t);
+}
+
+static void
+byteswap(unsigned char *G)
+{
+	int i;
+
+	for (i = 0; i < 16; i ++) {
+		unsigned char t;
+
+		t = G[i];
+		G[i] = G[31 - i];
+		G[31 - i] = t;
+	}
+}
+
+static uint32_t
+api_mul(unsigned char *G, size_t Glen,
+	const unsigned char *kb, size_t kblen, int curve)
+{
+	uint32_t x1[10], x2[10], x3[10], z2[10], z3[10];
+	uint32_t a[10], aa[10], b[10], bb[10];
+	uint32_t c[10], d[10], e[10], da[10], cb[10];
+	unsigned char k[32];
+	uint32_t swap;
+	int i;
+
+	(void)curve;
+
+	/*
+	 * Points are encoded over exactly 32 bytes. Multipliers must fit
+	 * in 32 bytes as well.
+	 * RFC 7748 mandates that the high bit of the last point byte must
+	 * be ignored/cleared.
+	 */
+	if (Glen != 32 || kblen > 32) {
+		return 0;
+	}
+	G[31] &= 0x7F;
+
+	/*
+	 * Byteswap the point encoding, because it uses little-endian, and
+	 * the generic decoding routine uses big-endian.
+	 */
+	byteswap(G);
+
+	/*
+	 * Decode the point ('u' coordinate). This should be reduced
+	 * modulo p, but we prefer to avoid the dependency on
+	 * br_i31_decode_reduce(). Instead, we use br_i31_decode_mod()
+	 * with a synthetic modulus of value 2^255 (this must work
+	 * since G was truncated to 255 bits), then use a conditional
+	 * subtraction. We use br_i31_decode_mod() and not
+	 * br_i31_decode(), because the ec_prime_i31 implementation uses
+	 * the former but not the latter.
+	 *    br_i31_decode_reduce(a, G, 32, C255_P);
+	 */
+	br_i31_zero(b, 0x108);
+	b[9] = 0x0080;
+	br_i31_decode_mod(a, G, 32, b);
+	a[0] = 0x107;
+	br_i31_sub(a, C255_P, NOT(br_i31_sub(a, C255_P, 0)));
+
+	/*
+	 * Initialise variables x1, x2, z2, x3 and z3. We set all of them
+	 * into Montgomery representation.
+	 */
+	br_i31_montymul(x1, a, C255_R2, C255_P, P0I);
+	memcpy(x3, x1, sizeof x1);
+	br_i31_zero(z2, C255_P[0]);
+	memcpy(x2, z2, sizeof z2);
+	x2[1] = 0x13000000;
+	memcpy(z3, x2, sizeof x2);
+
+	/*
+	 * kb[] is in big-endian notation, but possibly shorter than k[].
+	 */
+	memset(k, 0, (sizeof k) - kblen);
+	memcpy(k + (sizeof k) - kblen, kb, kblen);
+	k[31] &= 0xF8;
+	k[0] &= 0x7F;
+	k[0] |= 0x40;
+
+	/* obsolete
+	print_int_mont("x1", x1);
+	*/
+
+	swap = 0;
+	for (i = 254; i >= 0; i --) {
+		uint32_t kt;
+
+		kt = (k[31 - (i >> 3)] >> (i & 7)) & 1;
+		swap ^= kt;
+		cswap(x2, x3, swap);
+		cswap(z2, z3, swap);
+		swap = kt;
+
+		/* obsolete
+		print_int_mont("x2", x2);
+		print_int_mont("z2", z2);
+		print_int_mont("x3", x3);
+		print_int_mont("z3", z3);
+		*/
+
+		c255_add(a, x2, z2);
+		c255_mul(aa, a, a);
+		c255_sub(b, x2, z2);
+		c255_mul(bb, b, b);
+		c255_sub(e, aa, bb);
+		c255_add(c, x3, z3);
+		c255_sub(d, x3, z3);
+		c255_mul(da, d, a);
+		c255_mul(cb, c, b);
+
+		/* obsolete
+		print_int_mont("a ", a);
+		print_int_mont("aa", aa);
+		print_int_mont("b ", b);
+		print_int_mont("bb", bb);
+		print_int_mont("e ", e);
+		print_int_mont("c ", c);
+		print_int_mont("d ", d);
+		print_int_mont("da", da);
+		print_int_mont("cb", cb);
+		*/
+
+		c255_add(x3, da, cb);
+		c255_mul(x3, x3, x3);
+		c255_sub(z3, da, cb);
+		c255_mul(z3, z3, z3);
+		c255_mul(z3, z3, x1);
+		c255_mul(x2, aa, bb);
+		c255_mul(z2, C255_A24, e);
+		c255_add(z2, z2, aa);
+		c255_mul(z2, e, z2);
+
+		/* obsolete
+		print_int_mont("x2", x2);
+		print_int_mont("z2", z2);
+		print_int_mont("x3", x3);
+		print_int_mont("z3", z3);
+		*/
+	}
+	cswap(x2, x3, swap);
+	cswap(z2, z3, swap);
+
+	/*
+	 * Inverse z2 with a modular exponentiation. This is a simple
+	 * square-and-multiply algorithm; we mutualise most non-squarings
+	 * since the exponent contains almost only ones.
+	 */
+	memcpy(a, z2, sizeof z2);
+	for (i = 0; i < 15; i ++) {
+		c255_mul(a, a, a);
+		c255_mul(a, a, z2);
+	}
+	memcpy(b, a, sizeof a);
+	for (i = 0; i < 14; i ++) {
+		int j;
+
+		for (j = 0; j < 16; j ++) {
+			c255_mul(b, b, b);
+		}
+		c255_mul(b, b, a);
+	}
+	for (i = 14; i >= 0; i --) {
+		c255_mul(b, b, b);
+		if ((0xFFEB >> i) & 1) {
+			c255_mul(b, z2, b);
+		}
+	}
+	c255_mul(b, x2, b);
+
+	/*
+	 * To avoid a dependency on br_i31_from_monty(), we use
+	 * a Montgomery multiplication with 1.
+	 *    memcpy(x2, b, sizeof b);
+	 *    br_i31_from_monty(x2, C255_P, P0I);
+	 */
+	br_i31_zero(a, C255_P[0]);
+	a[1] = 1;
+	br_i31_montymul(x2, a, b, C255_P, P0I);
+
+	br_i31_encode(G, 32, x2);
+	byteswap(G);
+	return 1;
+}
+
+static size_t
+api_mulgen(unsigned char *R,
+	const unsigned char *x, size_t xlen, int curve)
+{
+	const unsigned char *G;
+	size_t Glen;
+
+	G = api_generator(curve, &Glen);
+	memcpy(R, G, Glen);
+	api_mul(R, Glen, x, xlen, curve);
+	return Glen;
+}
+
+static uint32_t
+api_muladd(unsigned char *A, const unsigned char *B, size_t len,
+	const unsigned char *x, size_t xlen,
+	const unsigned char *y, size_t ylen, int curve)
+{
+	/*
+	 * We don't implement this method, since it is used for ECDSA
+	 * only, and there is no ECDSA over Curve25519 (which instead
+	 * uses EdDSA).
+	 */
+	(void)A;
+	(void)B;
+	(void)len;
+	(void)x;
+	(void)xlen;
+	(void)y;
+	(void)ylen;
+	(void)curve;
+	return 0;
+}
+
+/* see bearssl_ec.h */
+const br_ec_impl br_ec_c25519_i31 = {
+	(uint32_t)0x20000000,
+	&api_generator,
+	&api_order,
+	&api_xoff,
+	&api_mul,
+	&api_mulgen,
+	&api_muladd
+};