Reworked the API

4 files changed, 97 insertions, 59 deletions

diff --git a/include/libuecc/ecc.h b/include/libuecc/ecc.h
index cf584cf..b8f8bc5 100644
--- a/include/libuecc/ecc.h
+++ b/include/libuecc/ecc.h
@@ -27,14 +27,14 @@
 #ifndef _LIBUECC_ECC_H_
 #define _LIBUECC_ECC_H_
 
-typedef struct _ecc_public_key_256 {
+typedef union _ecc_int_256 {
 	unsigned char p[32];
-} ecc_public_key_256;
 
-typedef struct _ecc_secret_key_256 {
+	/* old name */
 	unsigned char s[32];
-} ecc_secret_key_256;
+} ecc_int_256, ecc_secret_key_256, ecc_public_key_256;
 
+/* a point on the curve unpacked for efficient calculation */
 typedef struct _ecc_25519_work {
 	unsigned int X[32];
 	unsigned int Y[32];
@@ -43,20 +43,36 @@ typedef struct _ecc_25519_work {
 } ecc_25519_work;
 
 
-void ecc_25519_load(ecc_25519_work *out, const ecc_public_key_256 *in);
-void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in);
+void ecc_25519_load_xy(ecc_25519_work *out, const ecc_int_256 *x, const ecc_int_256 *y);
+void ecc_25519_store_xy(ecc_int_256 *x, ecc_int_256 *y, const ecc_25519_work *in);
+
+void ecc_25519_load_packed(ecc_25519_work *out, const ecc_int_256 *in);
+void ecc_25519_store_packed(ecc_int_256 *out, const ecc_25519_work *in);
 
 int ecc_25519_is_identity(const ecc_25519_work *in);
 void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2);
 void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in);
-void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base);
-void ecc_25519_scalarmult_base(ecc_25519_work *out, const ecc_secret_key_256 *n);
-
-int ecc_25519_secret_is_zero(const ecc_secret_key_256 *in);
-void ecc_25519_secret_add(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2);
-void ecc_25519_secret_sub(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2);
-void ecc_25519_secret_reduce(ecc_secret_key_256 *out, const ecc_secret_key_256 *in);
-void ecc_25519_secret_mult(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2);
-void ecc_25519_secret_sanitize(ecc_secret_key_256 *out, const ecc_secret_key_256 *in);
+void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_int_256 *n, const ecc_25519_work *base);
+void ecc_25519_scalarmult_base(ecc_25519_work *out, const ecc_int_256 *n);
+
+/* operations on elements of the prime field F_q for q = 2^252 + 27742317777372353535851937790883648493 */
+int ecc_25519_gf_is_zero(const ecc_int_256 *in);
+void ecc_25519_gf_add(ecc_int_256 *out, const ecc_int_256 *in1, const ecc_int_256 *in2);
+void ecc_25519_gf_sub(ecc_int_256 *out, const ecc_int_256 *in1, const ecc_int_256 *in2);
+void ecc_25519_gf_reduce(ecc_int_256 *out, const ecc_int_256 *in);
+void ecc_25519_gf_mult(ecc_int_256 *out, const ecc_int_256 *in1, const ecc_int_256 *in2);
+
+void ecc_25519_gf_sanitize_secret(ecc_int_256 *out, const ecc_int_256 *in);
+
+/* defines for the old names */
+#define ecc_25519_load            ecc_25519_load_packed
+#define ecc_25519_store           ecc_25519_store_packed
+
+#define ecc_25519_secret_is_zero  ecc_25519_gf_is_zero
+#define ecc_25519_secret_add      ecc_25519_gf_add
+#define ecc_25519_secret_sub      ecc_25519_gf_sub
+#define ecc_25519_secret_reduce   ecc_25519_gf_reduce
+#define ecc_25519_secret_mult     ecc_25519_gf_mult
+#define ecc_25519_secret_sanitize ecc_25519_gf_sanitize_secret
 
 #endif /* _LIBUECC_ECC_H_ */
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index edcee42..318d4f8 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 ec25519_secret.c)
+add_library(uecc STATIC ec25519.c ec25519_gf.c)
 
 install(TARGETS uecc
   ARCHIVE DESTINATION lib
diff --git a/src/ec25519.c b/src/ec25519.c
index bfb49a0..915bd2c 100644
--- a/src/ec25519.c
+++ b/src/ec25519.c
@@ -347,7 +347,40 @@ static void recip(unsigned int out[32], const unsigned int z[32]) {
 	/* 2^255 - 21 */ mult(out, t1, z11);
 }
 
-void ecc_25519_load(ecc_25519_work *out, const ecc_public_key_256 *in) {
+void ecc_25519_load_xy(ecc_25519_work *out, const ecc_int_256 *x, const ecc_int_256 *y) {
+	int i;
+
+	for (i = 0; i < 32; i++) {
+		out->X[i] = x->p[i];
+		out->Y[i] = y->p[i];
+		out->Z[i] = (i == 0);
+	}
+
+	mult(out->T, out->X, out->Y);
+}
+
+void ecc_25519_store_xy(ecc_int_256 *x, ecc_int_256 *y, const ecc_25519_work *in) {
+	unsigned int X[32], Y[32], Z[32];
+	int i;
+
+	recip(Z, in->Z);
+
+	if (x) {
+		mult(X, Z, in->X);
+		freeze(X);
+		for (i = 0; i < 32; i++)
+			x->p[i] = X[i];
+	}
+
+	if (y) {
+		mult(Y, Z, in->Y);
+		freeze(Y);
+		for (i = 0; i < 32; i++)
+			y->p[i] = Y[i];
+	}
+}
+
+void ecc_25519_load_packed(ecc_25519_work *out, const ecc_int_256 *in) {
 	static const unsigned int zero[32] = {0};
 	static const unsigned int one[32] = {1};
 
@@ -377,22 +410,11 @@ void ecc_25519_load(ecc_25519_work *out, const ecc_public_key_256 *in) {
 	mult(out->T, out->X, out->Y);
 }
 
-void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in) {
-	unsigned int x[32], y[32], z[32];
-	int i;
-
-	recip(z, in->Z);
-
-	mult(x, z, in->X);
-	mult(y, z, in->Y);
-
-	freeze(x);
-	freeze(y);
-
-	for (i = 0; i < 32; i++)
-		out->p[i] = x[i];
+void ecc_25519_store_packed(ecc_int_256 *out, const ecc_25519_work *in) {
+	ecc_int_256 y;
 
-	out->p[31] |= (y[0] << 7);
+	ecc_25519_store_xy(out, &y, in);
+	out->p[31] |= (y.p[0] << 7);
 }
 
 static const ecc_25519_work id = {{0}, {1}, {1}, {0}};
@@ -450,13 +472,13 @@ void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_255
 	mult(out->Z, F, G);
 }
 
-void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base) {
+void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_int_256 *n, const ecc_25519_work *base) {
 	ecc_25519_work Q2, Q2p;
 	ecc_25519_work cur = id;
 	int b, pos;
 
 	for (pos = 255; pos >= 0; --pos) {
-		b = n->s[pos / 8] >> (pos & 7);
+		b = n->p[pos / 8] >> (pos & 7);
 		b &= 1;
 
 		ecc_25519_double(&Q2, &cur);
@@ -483,6 +505,6 @@ static const ecc_25519_work default_base = {
 	 0x47, 0x4b, 0x4c, 0x81, 0xa6, 0x02, 0xfd, 0x29}
 };
 
-void ecc_25519_scalarmult_base(ecc_25519_work *out, const ecc_secret_key_256 *n) {
+void ecc_25519_scalarmult_base(ecc_25519_work *out, const ecc_int_256 *n) {
 	ecc_25519_scalarmult(out, n, &default_base);
 }
diff --git a/src/ec25519_secret.c b/src/ec25519_gf.c
index 7f3d987..6847cb1 100644
--- a/src/ec25519_secret.c
+++ b/src/ec25519_gf.c
@@ -57,43 +57,43 @@ static void select(unsigned char out[32], const unsigned char r[32], const unsig
 	}
 }
 
-int ecc_25519_secret_is_zero(const ecc_secret_key_256 *in) {
+int ecc_25519_gf_is_zero(const ecc_int_256 *in) {
 	int i;
-	ecc_secret_key_256 r;
+	ecc_int_256 r;
 	unsigned int bits;
 
-	ecc_25519_secret_reduce(&r, in);
+	ecc_25519_gf_reduce(&r, in);
 
 	for (i = 0; i < 32; i++)
-		bits |= r.s[i];
+		bits |= r.p[i];
 
 	return (((bits-1)>>8) & 1);
 }
 
-void ecc_25519_secret_add(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) {
+void ecc_25519_gf_add(ecc_int_256 *out, const ecc_int_256 *in1, const ecc_int_256 *in2) {
 	unsigned int j;
 	unsigned int u;
-	int nq = 1 - (in1->s[31]>>4) - (in2->s[31]>>4);
+	int nq = 1 - (in1->p[31]>>4) - (in2->p[31]>>4);
 
 	u = 0;
 	for (j = 0; j < 32; ++j) {
-		u += in1->s[j] + in2->s[j] + nq*q[j];
+		u += in1->p[j] + in2->p[j] + nq*q[j];
 
-		out->s[j] = u;
+		out->p[j] = u;
 		u = ASR(u, 8);
 	}
 }
 
-void ecc_25519_secret_sub(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) {
+void ecc_25519_gf_sub(ecc_int_256 *out, const ecc_int_256 *in1, const ecc_int_256 *in2) {
 	unsigned int j;
 	unsigned int u;
-	int nq = 8 - (in1->s[31]>>4) + (in2->s[31]>>4);
+	int nq = 8 - (in1->p[31]>>4) + (in2->p[31]>>4);
 
 	u = 0;
 	for (j = 0; j < 32; ++j) {
-		u += in1->s[j] - in2->s[j] + nq*q[j];
+		u += in1->p[j] - in2->p[j] + nq*q[j];
 
-		out->s[j] = u;
+		out->p[j] = u;
 		u = ASR(u, 8);
 	}
 }
@@ -120,13 +120,13 @@ static void reduce(unsigned char a[32]) {
 	select(a, out1, out2, IS_NEGATIVE(u1));
 }
 
-void ecc_25519_secret_reduce(ecc_secret_key_256 *out, const ecc_secret_key_256 *in) {
+void ecc_25519_gf_reduce(ecc_int_256 *out, const ecc_int_256 *in) {
 	int i;
 
 	for (i = 0; i < 32; i++)
-		out->s[i] = in->s[i];
+		out->p[i] = in->p[i];
 
-	reduce(out->s);
+	reduce(out->p);
 }
 
 /* Montgomery modular multiplication algorithm */
@@ -154,7 +154,7 @@ static void montgomery(unsigned char out[32], const unsigned char a[32], const u
 }
 
 
-void ecc_25519_secret_mult(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) {
+void ecc_25519_gf_mult(ecc_int_256 *out, const ecc_int_256 *in1, const ecc_int_256 *in2) {
 	/* 2^512 mod q */
 	static const unsigned char C[32] = {
 		0x01, 0x0f, 0x9c, 0x44, 0xe3, 0x11, 0x06, 0xa4,
@@ -168,21 +168,21 @@ void ecc_25519_secret_mult(ecc_secret_key_256 *out, const ecc_secret_key_256 *in
 	unsigned int i;
 
 	for (i = 0; i < 32; i++)
-		B[i] = in2->s[i];
+		B[i] = in2->p[i];
 
 	reduce(B);
 
-	montgomery(R, in1->s, B);
-	montgomery(out->s, R, C);
+	montgomery(R, in1->p, B);
+	montgomery(out->p, R, C);
 }
 
-void ecc_25519_secret_sanitize(ecc_secret_key_256 *out, const ecc_secret_key_256 *in) {
+void ecc_25519_gf_sanitize_secret(ecc_int_256 *out, const ecc_int_256 *in) {
 	int i;
 
 	for (i = 0; i < 32; i++)
-		out->s[i] = in->s[i];
+		out->p[i] = in->p[i];
 
-	out->s[0] &= 0xf8;
-	out->s[31] &= 0x7f;
-	out->s[31] |= 0x40;
+	out->p[0] &= 0xf8;
+	out->p[31] &= 0x7f;
+	out->p[31] |= 0x40;
 }