diff --git a/include/mcl/bn.hpp b/include/mcl/bn.hpp
index b56f6ba..fd69b4b 100644
--- a/include/mcl/bn.hpp
+++ b/include/mcl/bn.hpp
@@ -314,6 +314,8 @@ public:
 	}
 };
 
+#include <mcl/mapto_wb19.hpp>
+
 struct MapTo {
 	enum {
 		BNtype,
@@ -330,6 +332,7 @@ struct MapTo {
 	int type_;
 	int mapToMode_;
 	bool useOriginalG2cofactor_;
+	MapToG2_WB19 maptog2_wb19_;
 	MapTo()
 		: type_(0)
 		, mapToMode_(MCL_MAP_TO_MODE_ORIGINAL)
@@ -537,6 +540,11 @@ struct MapTo {
 			mapToMode_ = mode;
 			return true;
 			break;
+		case MCL_MAP_TO_MODE_WB19:
+			mapToMode_ = mode;
+			maptog2_wb19_.init();
+			return true;
+			break;
 		default:
 			return false;
 		}
diff --git a/include/mcl/curve_type.h b/include/mcl/curve_type.h
index dca749d..85ce7a5 100644
--- a/include/mcl/curve_type.h
+++ b/include/mcl/curve_type.h
@@ -39,5 +39,6 @@ enum {
 enum {
 	MCL_MAP_TO_MODE_ORIGINAL, // see MapTo::calcBN
 	MCL_MAP_TO_MODE_TRY_AND_INC, // try-and-incremental-x
-	MCL_MAP_TO_MODE_ETH2 // eth2.0 spec
+	MCL_MAP_TO_MODE_ETH2, // eth2.0 spec
+	MCL_MAP_TO_MODE_WB19
 };
diff --git a/include/mcl/mapto_wb19.hpp b/include/mcl/mapto_wb19.hpp
new file mode 100644
index 0000000..22f3770
--- /dev/null
+++ b/include/mcl/mapto_wb19.hpp
@@ -0,0 +1,608 @@
+#pragma once
+/**
+	@file
+	@brief map to G2 on BLS12-381 (must be included from mcl/bn.hpp)
+	@author MITSUNARI Shigeo(@herumi)
+	@license modified new BSD license
+	http://opensource.org/licenses/BSD-3-Clause
+	ref. https://eprint.iacr.org/2019/403 , https://github.com/algorand/bls_sigs_ref
+*/
+
+struct MapToG2_WB19 {
+	Fp2 xi;
+	Fp2 Ell2p_a;
+	Fp2 Ell2p_b;
+	Fp half;
+	mpz_class sqrtConst; // (p^2 - 9) / 16
+	Fp2 root4[4];
+	Fp2 etas[4];
+	Fp2 xnum[4];
+	Fp2 xden[3];
+	Fp2 ynum[4];
+	Fp2 yden[4];
+	struct Point {
+		Fp2 x, y, z;
+		bool isZero() const
+		{
+			return z.isZero();
+		}
+	};
+	// should be merged into ec.hpp
+	template<class G>
+	void neg(G& Q, const G& P) const
+	{
+		Q.x = P.x;
+		Fp2::neg(Q.y, P.y);
+		Q.z = P.z;
+	}
+	template<class G>
+	void add(G& R, const G& P, const G& Q) const
+	{
+		if (P.isZero()) {
+			R = Q;
+			return;
+		}
+		if (Q.isZero()) {
+			R = Q;
+			return;
+		}
+		Fp2 Z1Z1, Z2Z2, U1, U2, S1, S2;
+		Fp2::sqr(Z1Z1, P.z);
+		Fp2::sqr(Z2Z2, Q.z);
+		Fp2::mul(U1, P.x, Z2Z2);
+		Fp2::mul(U2, Q.x, Z1Z1);
+		Fp2::mul(S1, P.y, Q.z);
+		S1 *= Z2Z2;
+		Fp2::mul(S2, Q.y, P.z);
+		S2 *= Z1Z1;
+		if (U1 == U2 && S1 == S2) {
+			dbl(R, P);
+			return;
+		}
+		Fp2 H, I, J, rr, V;
+		Fp2::sub(H, U2, U1);
+		Fp2::add(I, H, H);
+		Fp2::sqr(I, I);
+		Fp2::mul(J, H, I);
+		Fp2::sub(rr, S2, S1);
+		rr += rr;
+		Fp2::mul(V, U1, I);
+		Fp2::mul(R.z, P.z, Q.z);
+		R.z *= H;
+		if (R.z.isZero()) {
+			R.x.clear();
+			R.y.clear();
+			return;
+		}
+		R.z += R.z;
+		Fp2::sqr(R.x, rr);
+		R.x -= J;
+		R.x -= V;
+		R.x -= V;
+		Fp2::sub(R.y, V, R.x);
+		R.y *= rr;
+		S1 *= J;
+		R.y -= S1;
+		R.y -= S1;
+	}
+	template<class G>
+	void dbl(G& Q, const G& P) const
+	{
+		Fp2 A, B, C, D, E, F;
+		Fp2::sqr(A, P.x);
+		Fp2::sqr(B, P.y);
+		Fp2::sqr(C, B);
+		Fp2::add(D, P.x, B);
+		Fp2::sqr(D, D);
+		D -= A;
+		D -= C;
+		D += D;
+		Fp2::add(E, A, A);
+		E += A;
+		Fp2::sqr(F, E);
+		Fp2::sub(Q.x, F, D);
+		Q.x -= D;
+		Fp2::mul(Q.z, P.y, P.z);
+		if (Q.z.isZero()) {
+			Q.x.clear();
+			Q.y.clear();
+			return;
+		}
+		Q.z += Q.z;
+		Fp2::sub(Q.y, D, Q.x);
+		Q.y *= E;
+		C += C;
+		C += C;
+		C += C;
+		Q.y -= C;
+	}
+	// P is on y^2 = x^3 + Ell2p_a x + Ell2p_b
+	bool isValidPoint(const Point& P) const
+	{
+    Fp2 y2, x2, z2, z4, t;
+    Fp2::sqr(x2, P.x);
+    Fp2::sqr(y2, P.y);
+    Fp2::sqr(z2, P.z);
+    Fp2::sqr(z4, z2);
+    Fp2::mul(t, z4, Ell2p_a);
+    t += x2;
+    t *= P.x;
+    z4 *= z2;
+    z4 *= Ell2p_b;
+    t += z4;
+    return y2 == t;
+	}
+	void init()
+	{
+		bool b;
+		xi.a = -2;
+		xi.b = -1;
+		Ell2p_a.a = 0;
+		Ell2p_a.b = 240;
+		Ell2p_b.a = 1012;
+		Ell2p_b.b = 1012;
+		half = -1;
+		half /= 2;
+		sqrtConst = Fp::getOp().mp;
+		sqrtConst *= sqrtConst;
+		sqrtConst -= 9;
+		sqrtConst /= 16;
+		const char *rv1Str = "0x6af0e0437ff400b6831e36d6bd17ffe48395dabc2d3435e77f76e17009241c5ee67992f72ec05f4c81084fbede3cc09";
+		root4[0].a = 1;
+		root4[0].b.clear();
+		root4[1].a.clear();
+		root4[1].b = 1;
+		root4[2].a.setStr(&b, rv1Str);
+		assert(b); (void)b;
+		root4[2].b = root4[2].a;
+		root4[3].a = root4[2].a;
+		Fp::neg(root4[3].b, root4[3].a);
+		const char *ev1Str = "0x699be3b8c6870965e5bf892ad5d2cc7b0e85a117402dfd83b7f4a947e02d978498255a2aaec0ac627b5afbdf1bf1c90";
+		const char *ev2Str = "0x8157cd83046453f5dd0972b6e3949e4288020b5b8a9cc99ca07e27089a2ce2436d965026adad3ef7baba37f2183e9b5";
+		const char *ev3Str = "0xab1c2ffdd6c253ca155231eb3e71ba044fd562f6f72bc5bad5ec46a0b7a3b0247cf08ce6c6317f40edbc653a72dee17";
+		const char *ev4Str = "0xaa404866706722864480885d68ad0ccac1967c7544b447873cc37e0181271e006df72162a3d3e0287bf597fbf7f8fc1";
+		Fp& ev1 = etas[0].a;
+		Fp& ev2 = etas[0].b;
+		Fp& ev3 = etas[2].a;
+		Fp& ev4 = etas[2].b;
+		ev1.setStr(&b, ev1Str);
+		assert(b); (void)b;
+		ev2.setStr(&b, ev2Str);
+		assert(b); (void)b;
+		Fp::neg(etas[1].a, ev2);
+		etas[1].b = ev1;
+		ev3.setStr(&b, ev3Str);
+		assert(b); (void)b;
+		ev4.setStr(&b, ev4Str);
+		assert(b); (void)b;
+		Fp::neg(etas[3].a, ev4);
+		etas[3].b = ev3;
+		init_iso();
+	}
+	void init_iso()
+	{
+		const char *tbl[] = {
+			"0x5c759507e8e333ebb5b7a9a47d7ed8532c52d39fd3a042a88b58423c50ae15d5c2638e343d9c71c6238aaaaaaaa97d6",
+			"0x11560bf17baa99bc32126fced787c88f984f87adf7ae0c7f9a208c6b4f20a4181472aaa9cb8d555526a9ffffffffc71a",
+			"0x11560bf17baa99bc32126fced787c88f984f87adf7ae0c7f9a208c6b4f20a4181472aaa9cb8d555526a9ffffffffc71e",
+			"0x8ab05f8bdd54cde190937e76bc3e447cc27c3d6fbd7063fcd104635a790520c0a395554e5c6aaaa9354ffffffffe38d",
+			"0x171d6541fa38ccfaed6dea691f5fb614cb14b4e7f4e810aa22d6108f142b85757098e38d0f671c7188e2aaaaaaaa5ed1",
+			"0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaa63",
+			"0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaa9f",
+			"0x1530477c7ab4113b59a4c18b076d11930f7da5d4a07f649bf54439d87d27e500fc8c25ebf8c92f6812cfc71c71c6d706",
+			"0x5c759507e8e333ebb5b7a9a47d7ed8532c52d39fd3a042a88b58423c50ae15d5c2638e343d9c71c6238aaaaaaaa97be",
+			"0x11560bf17baa99bc32126fced787c88f984f87adf7ae0c7f9a208c6b4f20a4181472aaa9cb8d555526a9ffffffffc71c",
+			"0x8ab05f8bdd54cde190937e76bc3e447cc27c3d6fbd7063fcd104635a790520c0a395554e5c6aaaa9354ffffffffe38f",
+			"0x124c9ad43b6cf79bfbf7043de3811ad0761b0f37a1e26286b0e977c69aa274524e79097a56dc4bd9e1b371c71c718b10",
+			"0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffa8fb",
+			"0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffa9d3",
+			"0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaa99",
+		};
+		bool b;
+		xnum[0].a.setStr(&b, tbl[0]); assert(b); (void)b;
+		xnum[0].b = xnum[0].a;
+		xnum[1].a.clear();
+		xnum[1].b.setStr(&b, tbl[1]); assert(b); (void)b;
+		xnum[2].a.setStr(&b, tbl[2]); assert(b); (void)b;
+		xnum[2].b.setStr(&b, tbl[3]); assert(b); (void)b;
+		xnum[3].a.setStr(&b, tbl[4]); assert(b); (void)b;
+		xnum[3].b.clear();
+		xden[0].a.clear();
+		xden[0].b.setStr(&b, tbl[5]); assert(b); (void)b;
+		xden[1].a = 0xc;
+		xden[1].b.setStr(&b, tbl[6]); assert(b); (void)b;
+		xden[2].a = 1;
+		xden[2].b = 0;
+		ynum[0].a.setStr(&b, tbl[7]); assert(b); (void)b;
+		ynum[0].b = ynum[0].a;
+		ynum[1].a.clear();
+		ynum[1].b.setStr(&b, tbl[8]); assert(b); (void)b;
+		ynum[2].a.setStr(&b, tbl[9]); assert(b); (void)b;
+		ynum[2].b.setStr(&b, tbl[10]); assert(b); (void)b;
+		ynum[3].a.setStr(&b, tbl[11]); assert(b); (void)b;
+		ynum[3].b.clear();
+		yden[0].a.setStr(&b, tbl[12]); assert(b); (void)b;
+		yden[0].b = yden[0].a;
+		yden[1].a.clear();
+		yden[1].b.setStr(&b, tbl[13]); assert(b); (void)b;
+		yden[2].a = 0x12;
+		yden[2].b.setStr(&b, tbl[14]); assert(b); (void)b;
+		yden[3].a = 1;
+		yden[3].b.clear();
+	}
+	template<size_t N>
+	void evalPoly(Fp2& y, const Fp2& x, const Fp2 *zpows, const Fp2 (&cof)[N]) const
+	{
+		Fp2::mul(y, zpows[0], cof[N - 1]);
+		for (size_t i = 1; i < N; i++) {
+			y *= x;
+			Fp2 t;
+			Fp2::mul(t, zpows[i], cof[N - 1 - i]);
+			y += t;
+		}
+	}
+	// refer (xnum, xden, ynum, yden)
+	void iso3(G2& Q, const Point& P) const
+	{
+		Fp2 zpows[4];
+		zpows[0] = 1;
+		Fp2::sqr(zpows[1], P.z);
+		Fp2::sqr(zpows[2], zpows[1]);
+		Fp2::mul(zpows[3], zpows[2], zpows[1]);
+		Fp2 mapvals[4];
+		evalPoly(mapvals[0], P.x, zpows, xnum);
+		evalPoly(mapvals[1], P.x, zpows, xden);
+		evalPoly(mapvals[2], P.x, zpows, ynum);
+		evalPoly(mapvals[3], P.x, zpows, yden);
+		mapvals[1] *= zpows[1];
+		mapvals[2] *= P.y;
+		mapvals[3] *= zpows[1];
+		mapvals[3] *= P.z;
+		Fp2::mul(Q.z, mapvals[1], mapvals[3]);
+		Fp2::mul(Q.x, mapvals[0], mapvals[3]);
+		Q.x *= Q.z;
+		Fp2 t;
+		Fp2::sqr(t, Q.z);
+		Fp2::mul(Q.y, mapvals[2], mapvals[1]);
+		Q.y *= t;
+	}
+	/*
+		(a+bi)*(-2-i) = (b-2a)-(a+2b)i
+	*/
+	void mul_xi(Fp2& y, const Fp2& x) const
+	{
+		Fp t;
+		Fp::sub(t, x.b, x.a);
+		t -= x.a;
+		Fp::add(y.b, x.b, x.b);
+		y.b += x.a;
+		Fp::neg(y.b, y.b);
+		y.a = t;
+	}
+	bool isNegSign(const Fp2& x) const
+	{
+		if (x.b > half) return true;
+		if (!x.b.isZero()) return false;
+		if (x.a > half) return true;
+		if (!x.b.isZero()) return false;
+		return false;
+	}
+	void osswu2_help(Point& P, const Fp2& t) const
+	{
+		Fp2 t2, t2xi;
+		Fp2::sqr(t2, t);
+		Fp2 den, den2;
+//		Fp2::mul(t2xi, t2, xi);
+		mul_xi(t2xi, t2);
+		den = t2xi;
+		Fp2::sqr(den2, den);
+		// (t^2 * xi)^2 + (t^2 * xi)
+		den += den2;
+		Fp2 x0_num, x0_den;
+		Fp2::add(x0_num, den, 1);
+		x0_num *= Ell2p_b;
+		if (den.isZero()) {
+			Fp2::mul(x0_den, Ell2p_a, xi);
+		} else {
+			Fp2::mul(x0_den, -Ell2p_a, den);
+		}
+		Fp2 x0_den2, x0_den3, gx0_den, gx0_num;
+		Fp2::sqr(x0_den2, x0_den);
+		Fp2::mul(x0_den3, x0_den2, x0_den);
+		gx0_den = x0_den3;
+
+		Fp2::mul(gx0_num, Ell2p_b, gx0_den);
+		Fp2 tmp, tmp1, tmp2;
+		Fp2::mul(tmp, Ell2p_a, x0_num);
+		tmp *= x0_den2;
+		gx0_num += tmp;
+		Fp2::sqr(tmp, x0_num);
+		tmp *= x0_num;
+		gx0_num += tmp;
+
+		Fp2::sqr(tmp1, gx0_den); // x^2
+		Fp2::sqr(tmp2, tmp1); // x^4
+		tmp1 *= tmp2;
+		tmp1 *= gx0_den; // x^7
+		Fp2::mul(tmp2, gx0_num, tmp1);
+		tmp1 *= tmp2;
+		tmp1 *= gx0_den;
+		Fp2 candi;
+		Fp2::pow(candi, tmp1, sqrtConst);
+		candi *= tmp2;
+		bool isNegT = isNegSign(t);
+		for (size_t i = 0; i < CYBOZU_NUM_OF_ARRAY(root4); i++) {
+			Fp2::mul(P.y, candi, root4[i]);
+			Fp2::sqr(tmp, P.y);
+			tmp *= gx0_den;
+			if (tmp == gx0_num) {
+				if (isNegSign(P.y) != isNegT) {
+					Fp2::neg(P.y, P.y);
+				}
+				Fp2::mul(P.x, x0_num, x0_den);
+				P.y *= x0_den3;
+				P.z = x0_den;
+				return;
+			}
+		}
+		Fp2 x1_num, x1_den, gx1_num, gx1_den;
+		Fp2::mul(x1_num, t2xi, x0_num);
+		x1_den = x0_den;
+		Fp2::mul(gx1_num, den2, t2xi);
+		gx1_num *= gx0_num;
+		gx1_den = gx0_den;
+		candi *= t2;
+		candi *= t;
+		for (size_t i = 0; i < CYBOZU_NUM_OF_ARRAY(etas); i++) {
+			Fp2::mul(P.y, candi, etas[i]);
+			Fp2::sqr(tmp, P.y);
+			tmp *= gx1_den;
+			if (tmp == gx1_num) {
+				if (isNegSign(P.y) != isNegT) {
+					Fp2::neg(P.y, P.y);
+				}
+				Fp2::mul(P.x, x1_num, x1_den);
+				Fp2::sqr(tmp, x1_den);
+				P.y *= tmp;
+				P.y *= x1_den;
+				P.z = x1_den;
+				return;
+			}
+		}
+		assert(0);
+	}
+	void h2_chain(G2& t1, const G2& P) const
+	{
+		G2 t0, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15;
+		t0 = P;
+		dbl(t1, t0);
+		add(t4, t1, t0);
+		add(t2, t4, t1);
+		add(t3, t2, t1);
+		add(t11, t3, t1);
+		add(t9, t11, t1);
+		add(t10, t9, t1);
+		add(t5, t10, t1);
+		add(t7, t5, t1);
+		add(t15, t7, t1);
+		add(t13, t15, t1);
+		add(t6, t13, t1);
+		add(t14, t6, t1);
+		add(t12, t14, t1);
+		add(t8, t12, t1);
+		dbl(t1, t6);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t13);
+		for (size_t i = 0; i < 2; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 9; i++) dbl(t1, t1);
+		add(t1, t1, t8);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t11);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t13);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t11);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t8);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 9; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t11);
+		for (size_t i = 0; i < 2; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 9; i++) dbl(t1, t1);
+		add(t1, t1, t8);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t13);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 11; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 7; i++) dbl(t1, t1);
+		add(t1, t1, t12);
+		for (size_t i = 0; i < 7; i++) dbl(t1, t1);
+		add(t1, t1, t7);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t12);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t14);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t13);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t13);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t10);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t10);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 10; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t14);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t15);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t8);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t12);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t15);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 7; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t15);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t14);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t8);
+		for (size_t i = 0; i < 10; i++) dbl(t1, t1);
+		add(t1, t1, t6);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 3; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 9; i++) dbl(t1, t1);
+		add(t1, t1, t13);
+		for (size_t i = 0; i < 7; i++) dbl(t1, t1);
+		add(t1, t1, t12);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t11);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t10);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t4);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t10);
+		for (size_t i = 0; i < 7; i++) dbl(t1, t1);
+		add(t1, t1, t7);
+		for (size_t i = 0; i < 3; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+		for (size_t i = 0; i < 4; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 8; i++) dbl(t1, t1);
+		add(t1, t1, t9);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t8);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t7);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t6);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t4);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t4);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t4);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t5);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 7; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t4);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 3; i++) dbl(t1, t1);
+		add(t1, t1, t0);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 6; i++) dbl(t1, t1);
+		add(t1, t1, t3);
+		for (size_t i = 0; i < 5; i++) dbl(t1, t1);
+		add(t1, t1, t2);
+	}
+	void mx_chain(G2& Q, const G2& P) const
+	{
+		G2 T;
+		dbl(T, P);
+		const size_t tbl[] = { 2, 3, 9, 32, 16 };
+		for (size_t i = 0; i < CYBOZU_NUM_OF_ARRAY(tbl); i++) {
+			add(T, T, P);
+			for (size_t j = 0; j < tbl[i]; j++) {
+				dbl(T, T);
+			}
+		}
+		Q = T;
+	}
+	void clear_h2(G2& Q, const G2& P) const
+	{
+#if 0
+		mcl::bn::BN::param.mapTo.mulByCofactorBLS12fast(Q, P);
+#else
+		G2 work, work2;
+		h2_chain(work, P);
+		dbl(work2, work);
+		add(work2, work, work2);
+		mx_chain(work, work2);
+		mx_chain(work, work);
+		neg(work2, work2);
+		add(Q, work, work2);
+#endif
+	}
+	void opt_swu2_map(G2& P, const Fp2& t, const Fp2 *t2 = 0) const
+	{
+		Point Pp;
+		osswu2_help(Pp, t);
+		if (t2) {
+			Point P2;
+			osswu2_help(P2, *t2);
+			add(Pp, Pp, P2);
+		}
+		iso3(P, Pp);
+		clear_h2(P, P);
+	}
+};
+