diff --git a/include/mcl/she.h b/include/mcl/she.h
index 6384b47..f4f94be 100644
--- a/include/mcl/she.h
+++ b/include/mcl/she.h
@@ -100,11 +100,11 @@ MCLSHE_DLL_API int sheEncG2(sheCipherTextG2 *c, const shePublicKey *pub, int64_t
 MCLSHE_DLL_API int sheEncGT(sheCipherTextGT *c, const shePublicKey *pub, int64_t m);
 
 /*
-	decode c and set m[2]. plaintext is int64_t(m[1] << 32) + m[0]
+	decode c and set m
 	return 0 if success
 */
-MCLSHE_DLL_API int sheDecG1(uint32_t m[2], const sheSecretKey *sec, const sheCipherTextG1 *c);
-MCLSHE_DLL_API int sheDecGT(uint32_t m[2], const sheSecretKey *sec, const sheCipherTextGT *c);
+MCLSHE_DLL_API int sheDecG1(int64_t *m, const sheSecretKey *sec, const sheCipherTextG1 *c);
+MCLSHE_DLL_API int sheDecGT(int64_t *m, const sheSecretKey *sec, const sheCipherTextGT *c);
 
 // return 0 if success
 // z = x + y
diff --git a/src/she_c_impl.hpp b/src/she_c_impl.hpp
index 885000f..d4d5dad 100644
--- a/src/she_c_impl.hpp
+++ b/src/she_c_impl.hpp
@@ -217,24 +217,22 @@ int sheEncGT(sheCipherTextGT *c, const shePublicKey *pub, int64_t m)
 }
 
 template<class CT>
-int decT(uint32_t m[2], const sheSecretKey *sec, const CT *c)
+int decT(int64_t *m, const sheSecretKey *sec, const CT *c)
 	try
 {
-	uint64_t dec = uint64_t(cast(sec)->dec(*cast(c)));
-	m[0] = uint32_t(dec);
-	m[1] = uint32_t(dec >> 32);
+	*m = cast(sec)->dec(*cast(c));
 	return 0;
 } catch (std::exception& e) {
 	printf("err %s\n", e.what());
 	return -1;
 }
 
-int sheDecG1(uint32_t m[2], const sheSecretKey *sec, const sheCipherTextG1 *c)
+int sheDecG1(int64_t *m, const sheSecretKey *sec, const sheCipherTextG1 *c)
 {
 	return decT(m, sec, c);
 }
 
-int sheDecGT(uint32_t m[2], const sheSecretKey *sec, const sheCipherTextGT *c)
+int sheDecGT(int64_t *m, const sheSecretKey *sec, const sheCipherTextGT *c)
 {
 	return decT(m, sec, c);
 }
diff --git a/test/she_c_test.hpp b/test/she_c_test.hpp
index 66a8ec1..cd58dbf 100644
--- a/test/she_c_test.hpp
+++ b/test/she_c_test.hpp
@@ -21,11 +21,6 @@ CYBOZU_TEST_AUTO(init)
 	CYBOZU_TEST_EQUAL(ret, 0);
 }
 
-int64_t toInt(const uint32_t m[2])
-{
-	return m[0] + (int64_t(m[1]) << 32);
-}
-
 CYBOZU_TEST_AUTO(encDec)
 {
 	sheSecretKey sec;
@@ -39,11 +34,11 @@ CYBOZU_TEST_AUTO(encDec)
 	sheEncG1(&c1, &pub, m);
 	sheEncGT(&ct, &pub, m);
 
-	uint32_t dec[2];
-	CYBOZU_TEST_EQUAL(sheDecG1(dec, &sec, &c1), 0);
-	CYBOZU_TEST_EQUAL(toInt(dec), m);
-	CYBOZU_TEST_EQUAL(sheDecGT(dec, &sec, &ct), 0);
-	CYBOZU_TEST_EQUAL(toInt(dec), m);
+	int64_t dec;
+	CYBOZU_TEST_EQUAL(sheDecG1(&dec, &sec, &c1), 0);
+	CYBOZU_TEST_EQUAL(dec, m);
+	CYBOZU_TEST_EQUAL(sheDecGT(&dec, &sec, &ct), 0);
+	CYBOZU_TEST_EQUAL(dec, m);
 }
 
 CYBOZU_TEST_AUTO(addMul)
@@ -62,9 +57,9 @@ CYBOZU_TEST_AUTO(addMul)
 	sheEncG2(&c2, &pub, m2);
 	sheMul(&ct, &c1, &c2);
 
-	uint32_t dec[2];
-	CYBOZU_TEST_EQUAL(sheDecGT(dec, &sec, &ct), 0);
-	CYBOZU_TEST_EQUAL(toInt(dec), m1 * m2);
+	int64_t dec;
+	CYBOZU_TEST_EQUAL(sheDecGT(&dec, &sec, &ct), 0);
+	CYBOZU_TEST_EQUAL(dec, m1 * m2);
 }
 
 CYBOZU_TEST_AUTO(allOp)
@@ -95,9 +90,9 @@ CYBOZU_TEST_AUTO(allOp)
 	sheMulGT(&ct, &ct, -4); // 160 * (m1 - m2) * (m3 - m4)
 
 	int64_t t = 160 * (m1 - m2) * (m3 - m4);
-	uint32_t dec[2];
-	CYBOZU_TEST_EQUAL(sheDecGT(dec, &sec, &ct), 0);
-	CYBOZU_TEST_EQUAL(toInt(dec), t);
+	int64_t dec;
+	CYBOZU_TEST_EQUAL(sheDecGT(&dec, &sec, &ct), 0);
+	CYBOZU_TEST_EQUAL(dec, t);
 }
 
 CYBOZU_TEST_AUTO(rerand)
@@ -126,9 +121,9 @@ CYBOZU_TEST_AUTO(rerand)
 	sheReRandGT(&ct2, &pub);
 	sheAddGT(&ct1, &ct1, &ct2);
 
-	uint32_t dec[2];
-	CYBOZU_TEST_EQUAL(sheDecGT(dec, &sec, &ct1), 0);
-	CYBOZU_TEST_EQUAL(toInt(dec), m1 * m2 + m3);
+	int64_t dec;
+	CYBOZU_TEST_EQUAL(sheDecGT(&dec, &sec, &ct1), 0);
+	CYBOZU_TEST_EQUAL(dec, m1 * m2 + m3);
 }
 
 CYBOZU_TEST_AUTO(serialize)