More renames, added secret key arithmetic

3 files changed, 198 insertions, 17 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1bad208..edcee42 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,6 +1,6 @@
 include_directories(${LIBUECC_SOURCE_DIR}/include)
 
-add_library(uecc STATIC ec25519.c)
+add_library(uecc STATIC ec25519.c ec25519_secret.c)
 
 install(TARGETS uecc
   ARCHIVE DESTINATION lib
diff --git a/src/ec25519.c b/src/ec25519.c
index effbfc6..7887f61 100644
--- a/src/ec25519.c
+++ b/src/ec25519.c
@@ -74,7 +74,7 @@ static void squeeze(unsigned int a[32]) {
 
 static const unsigned int minusp[32] = {
 	19, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128
-} ;
+};
 
 static void freeze(unsigned int a[32]) {
 	unsigned int aorig[32];
@@ -156,13 +156,13 @@ static int check_equal(const unsigned int x[32], const unsigned int y[32]) {
 	return (1-(1 & ((differentbits - 1) >> 16)));
 }
 
-static void selectw(ec_25519_work *out, const ec_25519_work *r, const ec_25519_work *s, unsigned int b) {
+static void selectw(ecc_25519_work *out, const ecc_25519_work *r, const ecc_25519_work *s, unsigned int b) {
 	unsigned int j;
 	unsigned int t;
 	unsigned int bminus1;
 
 	bminus1 = b - 1;
-	for (j = 0;j < 32;++j) {
+	for (j = 0; j < 32; ++j) {
 		t = bminus1 & (r->X[j] ^ s->X[j]);
 		out->X[j] = s->X[j] ^ t;
 
@@ -340,7 +340,7 @@ static void recip(unsigned int out[32], const unsigned int z[32]) {
 	/* 2^255 - 21 */ mult(out, t1, z11);
 }
 
-void ec_25519_load(ec_25519_work *out, const ec_public_key_256 *in) {
+void ecc_25519_load(ecc_25519_work *out, const ecc_public_key_256 *in) {
 	int i;
 	unsigned int X2[32], d_X2[32] = {0x04, 0x6d, 0x07} /* 486660 */, a_X2[32] = {0x08, 0x6d, 0x07} /* 486664 */, _1_a_X2[32], d_X2_a_X2[32], Y[32], Yt[32];
 
@@ -362,7 +362,7 @@ void ec_25519_load(ec_25519_work *out, const ec_public_key_256 *in) {
 	select(out->Y, Y, Yt, (in->p[31] >> 7) ^ (Y[0] & 1));
 }
 
-void ec_25519_store(ec_public_key_256 *out, const ec_25519_work *in) {
+void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in) {
 	unsigned int x[32], y[32], z[32];
 	int i;
 
@@ -380,9 +380,9 @@ void ec_25519_store(ec_public_key_256 *out, const ec_25519_work *in) {
 	out->p[31] |= (y[0] << 7);
 }
 
-static const ec_25519_work infty = {{0}, {0}, {1}};
+static const ecc_25519_work infty = {{0}, {0}, {1}};
 
-void ec_25519_double(ec_25519_work *out, const ec_25519_work *in) {
+void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in) {
 	unsigned int A[32], B[32], C[32], D[32], E[32], U[32], t0[32], t1[32], t2[32], t3[32], t4[32], t5[32];
 
 	square(A, in->X);
@@ -403,7 +403,7 @@ void ec_25519_double(ec_25519_work *out, const ec_25519_work *in) {
 	selectw(out, &infty, out, check_zero(out->X)*check_zero(out->Y));
 }
 
-void ec_25519_add(ec_25519_work *out, const ec_25519_work *in1, const ec_25519_work *in2) {
+void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2) {
 	unsigned int A[32], B[32], C[32], D[32], E[32], H[32], I[32], t0[32], t1[32], t2[32], t3[32], t4[32], t5[32], t6[32], t7[32], t8[32];
 
 	mult(A, in1->Z, in2->Z);
@@ -429,8 +429,8 @@ void ec_25519_add(ec_25519_work *out, const ec_25519_work *in1, const ec_25519_w
 	selectw(out, in2, out, check_zero(t2));
 }
 
-void ec_25519_scalarmult(ec_25519_work *out, const ec_secret_key_256 *n, const ec_25519_work *base) {
-	ec_25519_work Q2, Q2p, cur;
+void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base) {
+	ecc_25519_work Q2, Q2p, cur;
 	int i, b, pos;
 
 	for (i = 0; i < 32; i++) {
@@ -439,12 +439,12 @@ void ec_25519_scalarmult(ec_25519_work *out, const ec_secret_key_256 *n, const e
 		cur.Z[i] = (i == 0);
 	}
 
-	for (pos = 254;pos >= 0;--pos) {
+	for (pos = 255; pos >= 0; --pos) {
 		b = n->s[pos / 8] >> (pos & 7);
 		b &= 1;
 
-		ec_25519_double(&Q2, &cur);
-		ec_25519_add(&Q2p, &Q2, base);
+		ecc_25519_double(&Q2, &cur);
+		ecc_25519_add(&Q2p, &Q2, base);
 		selectw(&cur, &Q2, &Q2p, b);
 	}
 
@@ -455,7 +455,7 @@ void ec_25519_scalarmult(ec_25519_work *out, const ec_secret_key_256 *n, const e
 	}
 }
 
-static const ec_25519_work default_base = {
+static const ecc_25519_work default_base = {
 	{0x51, 0x89, 0xfa, 0x46, 0xa0, 0xc0, 0x8b, 0x3d,
          0x30, 0x60, 0xf1, 0x7d, 0x2a, 0xec, 0xcd, 0xf3,
 	 0x24, 0x50, 0x96, 0x62, 0x21, 0xfc, 0xe6, 0x18,
@@ -467,6 +467,6 @@ static const ec_25519_work default_base = {
 	{1}
 };
 
-void ec_25519_scalarmult_base(ec_25519_work *out, const ec_secret_key_256 *n) {
-	ec_25519_scalarmult(out, n, &default_base);
+void ecc_25519_scalarmult_base(ecc_25519_work *out, const ecc_secret_key_256 *n) {
+	ecc_25519_scalarmult(out, n, &default_base);
 }
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);
+}
+