More renames, added secret key arithmetic

1 files changed, 181 insertions, 0 deletions

diff --git a/src/ec25519_secret.c b/src/ec25519_secret.c
new file mode 100644
index 0000000..0a58629
--- /dev/null
+++ b/src/ec25519_secret.c
@@ -0,0 +1,181 @@
+/*
+  Copyright (c) 2012, Matthias Schiffer <mschiffer@universe-factory.net>
+  Partly based on public domain code by Matthew Dempsky and D. J. Bernstein.
+  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.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
+*/
+
+/*
+  Simple finite field operations on the prime field F_p for
+  p = 2^252 + 27742317777372353535851937790883648493, which
+  is the order of the base point used for ec25519
+*/
+
+#include <libuecc/ecc.h>
+
+
+#define IS_NEGATIVE(n) ((int)((((unsigned)n) >> (8*sizeof(n)-1))&1))
+
+
+static const unsigned char q[32] = {
+	0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
+	0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
+};
+
+
+static void select(unsigned char out[32], const unsigned char r[32], const unsigned char s[32], unsigned int b) {
+	unsigned int j;
+	unsigned int t;
+	unsigned int bminus1;
+
+	bminus1 = b - 1;
+	for (j = 0;j < 32;++j) {
+		t = bminus1 & (r[j] ^ s[j]);
+		out[j] = s[j] ^ t;
+	}
+}
+
+void ecc_25519_add_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) {
+	unsigned int j;
+	int u1, u2, u3;
+	unsigned char out1[32], out2[32], out3[32];
+
+	u1 = u2 = u3 = 0;
+	for (j = 0; j < 31; ++j) {
+		u1 += in1->s[j] + in2->s[j];
+		u2 += in1->s[j] + in2->s[j] - 8*q[j];
+		u3 += in1->s[j] + in2->s[j] - 16*q[j];
+
+		out1[j] = u1; out2[j] = u2; out3[j] = u3;
+		u1 = (u1+IS_NEGATIVE(u1))/256 - IS_NEGATIVE(u1);
+		u2 = (u2+IS_NEGATIVE(u2))/256 - IS_NEGATIVE(u2);
+		u3 = (u3+IS_NEGATIVE(u3))/256 - IS_NEGATIVE(u3);
+	}
+	u1 += in1->s[31] + in2->s[31];
+	u2 += in1->s[31] + in2->s[31] - 8*q[31];
+	u3 += in1->s[31] + in2->s[31] - 16*q[31];
+	out1[31] = u1; out2[31] = u2; out3[31] = u3;
+
+	select(out->s, out1, out2, (u1 >> 8) & 1);
+	select(out->s, out->s, out3, ((u1 >> 8) & (u2 >> 8)) & 1);
+}
+
+void ecc_25519_sub_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) {
+	unsigned int j;
+	int u1, u2, u3;
+	unsigned char out1[32], out2[32], out3[32];
+
+	u1 = u2 = u3 = 0;
+	for (j = 0; j < 31; ++j) {
+		u1 += in1->s[j] - in2->s[j] + 16*q[j];
+		u2 += in1->s[j] - in2->s[j] + 8*q[j];
+		u3 += in1->s[j] - in2->s[j];
+
+		out1[j] = u1; out2[j] = u2; out3[j] = u3;
+		u1 = (u1+IS_NEGATIVE(u1))/256 - IS_NEGATIVE(u1);
+		u2 = (u2+IS_NEGATIVE(u2))/256 - IS_NEGATIVE(u2);
+		u3 = (u3+IS_NEGATIVE(u3))/256 - IS_NEGATIVE(u3);
+	}
+	u1 += in1->s[31] - in2->s[31] + 16*q[31];
+	u2 += in1->s[31] - in2->s[31] + 8*q[31];
+	u3 += in1->s[31] - in2->s[31];
+	out1[31] = u1; out2[31] = u2; out3[31] = u3;
+
+	select(out->s, out1, out2, (u1 >> 8) & 1);
+	select(out->s, out->s, out3, ((u1 >> 8) & (u2 >> 8)) & 1);
+}
+
+static void reduce(unsigned char a[32]) {
+	unsigned int j;
+	int nq = a[31] >> 4;
+	int u1, u2;
+	unsigned char out1[32], out2[32];
+
+	u1 = u2 = 0;
+	for (j = 0; j < 31; ++j) {
+		u1 += a[j] - nq*q[j];
+		u2 += a[j] - (nq-1)*q[j];
+
+		out1[j] = u1; out2[j] = u2;
+		u1 = (u1+IS_NEGATIVE(u1))/256 - IS_NEGATIVE(u1);
+		u2 = (u2+IS_NEGATIVE(u2))/256 - IS_NEGATIVE(u2);
+	}
+	u1 += a[31] - nq*q[31];
+	u2 += a[31] - (nq-1)*q[31];
+	out1[31] = u1; out2[31] = u2;
+
+	select(a, out1, out2, IS_NEGATIVE(u1));
+}
+
+/* Montgomery modular multiplication algorithm */
+static void montgomery(unsigned char out[32], const unsigned char a[32], const unsigned char b[32]) {
+	unsigned int a_i;
+	unsigned int i, j;
+	unsigned int r0;
+	unsigned int u;
+
+	for (i = 0; i < 32; i++)
+		out[i] = 0;
+
+	for (i = 0; i < 256; i++) {
+		a_i = a[i / 8] >> (i & 7);
+		a_i &= 1;
+
+		u = out[0] + a_i*b[0];
+		r0 = u & 1;
+		u += r0 * q[0];
+
+		for (j = 1; j < 32; ++j) {
+			u += (out[j] + a_i*b[j] + r0*q[j]) << 8;
+			out[j-1] = (u >> 1) & 255;
+			u >>= 8;
+		}
+
+		out[31] = u >> 1;
+	}
+}
+
+
+void ecc_25519_mult_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) {
+	/* 2^512 mod p */
+	static const unsigned char C[32] = {
+		0x01, 0x0f, 0x9c, 0x44, 0xe3, 0x11, 0x06, 0xa4,
+		0x47, 0x93, 0x85, 0x68, 0xa7, 0x1b, 0x0e, 0xd0,
+		0x65, 0xbe, 0xf5, 0x17, 0xd2, 0x73, 0xec, 0xce,
+		0x3d, 0x9a, 0x30, 0x7c, 0x1b, 0x41, 0x99, 0x03
+	};
+
+	unsigned char B[32];
+	unsigned char R[32];
+	unsigned int i;
+
+	for (i = 0; i < 32; i++)
+		B[i] = in2->s[i];
+
+	reduce(B);
+
+	montgomery(R, in1->s, B);
+	montgomery(out->s, R, C);
+}
+