add dblCTProj

herumi · Feb 13, 2024 · 3cf65bb · 3cf65bb
1 parent 7042a44
commit 3cf65bb
Show file tree

Hide file tree

Showing 2 changed files with 57 additions and 10 deletions.
diff --git a/include/mcl/ec.hpp b/include/mcl/ec.hpp
@@ -505,17 +505,23 @@ void addJacobi(E& R, const E& P, const E& Q)
 /*
 	accept P == Q
 	https://github.com/apache/incubator-milagro-crypto-c/blob/fa0a45a3/src/ecp.c.in#L767-L976
+	// 14M
 	(x, y, z) is zero <=> x = 0, y = 1, z = 0
 */
+template<class E>
+void clearCTProj(E& P)
+{
+	P.x.clear();
+	P.y = 1;
+	P.z.clear();
+}
+
 template<class E>
 void addCTProj(E& R, const E& P, const E& Q)
 {
 	typedef typename E::Fp F;
 	assert(E::a_ == 0);
-	F b3;
-	F::add(b3, E::b_, E::b_);
-	b3 += E::b_;
-	F t0, t1, t2, t3, t4, x3, y3, z3;
+	F t0, t1, t2, t3, t4, x3, y3;
 	F::mul(t0, P.x, Q.x);
 	F::mul(t1, P.y, Q.y);
 	F::mul(t2, P.z, Q.z);
@@ -536,19 +542,44 @@ void addCTProj(E& R, const E& P, const E& Q)
 	F::sub(y3, x3, y3);
 	F::add(x3, t0, t0);
 	F::add(t0, t0, x3);
-	t2 *= b3;
-	F::add(z3, t1, t2);
+	t2 *= E::b3_;
+	F::add(R.z, t1, t2);
 	F::sub(t1, t1, t2);
-	y3 *= b3;
+	y3 *= E::b3_;
 	F::mul(x3, y3, t4);
 	F::mul(t2, t3, t1);
 	F::sub(R.x, t2, x3);
 	F::mul(y3, y3, t0);
-	F::mul(t1, t1, z3);
+	F::mul(t1, t1, R.z);
 	F::add(R.y, y3, t1);
 	F::mul(t0, t0, t3);
-	F::mul(z3, z3, t4);
-	F::add(R.z, z3, t0);
+	F::mul(R.z, R.z, t4);
+	F::add(R.z, R.z, t0);
+}
+template<class E>
+void dblCTProj(E& R, const E& P)
+{
+	typedef typename E::Fp F;
+	assert(E::a_ == 0);
+	F t0, t1, t2, x3, y3;
+	F::sqr(t0, P.y);
+	F::mul(t1, P.y, P.z);
+	F::sqr(t2, P.z);
+	F::add(R.z, t0, t0);
+	F::add(R.z, R.z, R.z);
+	F::add(R.z, R.z, R.z);
+	F::mul(t2, t2, E::b3_);
+	F::mul(x3, t2, P.z);
+	F::add(y3, t0, t2);
+	F::mul(R.z, R.z, t1);
+	F::add(t1, t2, t2);
+	F::add(t2, t2, t1);
+	F::mul(t1, P.x, P.y);
+	F::sub(t0, t0, t2);
+	F::mul(R.y, y3, t0);
+	R.y += x3;
+	F::mul(R.x, t0, t1);
+	R.x += R.x;
 }
 
 template<class E>
@@ -1237,6 +1268,7 @@ class EcT : public fp::Serializable<EcT<_Fp> > {
 	static int mode_;
 	static Fp a_;
 	static Fp b_;
+	static Fp b3_;
 	static int specialA_;
 	static int ioMode_;
 	/*
@@ -1294,6 +1326,7 @@ class EcT : public fp::Serializable<EcT<_Fp> > {
 	{
 		a_ = a;
 		b_ = b;
+		b3_ = b * 3;
 		if (a_.isZero()) {
 			specialA_ = ec::Zero;
 		} else if (a_ == -3) {
@@ -2100,6 +2133,7 @@ class EcT : public fp::Serializable<EcT<_Fp> > {
 
 template<class Fp> Fp EcT<Fp>::a_;
 template<class Fp> Fp EcT<Fp>::b_;
+template<class Fp> Fp EcT<Fp>::b3_;
 template<class Fp> int EcT<Fp>::specialA_;
 template<class Fp> int EcT<Fp>::ioMode_;
 template<class Fp> bool EcT<Fp>::verifyOrder_;

diff --git a/test/ec_test.cpp b/test/ec_test.cpp
@@ -626,6 +626,19 @@ struct Test {
 		mcl::ec::addCTProj(Q, Zero, Zero);
 		Ec::add(R, Zero, Zero);
 		CYBOZU_TEST_EQUAL(Q, R);
+		mcl::ec::addCTProj(Q, Q, Q);
+		Ec::add(R, R, R);
+		CYBOZU_TEST_EQUAL(Q, R);
+
+		// dbl
+		mcl::ec::dblCTProj(P, Q);
+		Ec::dbl(R, R);
+		CYBOZU_TEST_EQUAL(Q, R);
+		mcl::ec::dblCTProj(Q, Q);
+		Ec::dbl(R, R);
+		CYBOZU_TEST_EQUAL(Q, R);
+		mcl::ec::dblCTProj(Q, Zero);
+		CYBOZU_TEST_EQUAL(Q, Zero);
 	}
 	void ProjJacobi() const
 	{