add blsSecretKeySetLittleEndianMod

3 files changed, 38 insertions, 3 deletions

diff --git a/include/bls/bls.h b/include/bls/bls.h
index 39cbf40..5e590ae 100644
--- a/include/bls/bls.h
+++ b/include/bls/bls.h
@@ -87,6 +87,9 @@ BLS_DLL_API void blsIdSetInt(blsId *id, int x);
 // return 0 if success
 // mask buf with (1 << (bitLen(r) - 1)) - 1 if buf >= r
 BLS_DLL_API int blsSecretKeySetLittleEndian(blsSecretKey *sec, const void *buf, mclSize bufSize);
+// return 0 if success (bufSize <= 64) else -1
+// set (buf mod r) to sec
+BLS_DLL_API int blsSecretKeySetLittleEndianMod(blsSecretKey *sec, const void *buf, mclSize bufSize);
 
 BLS_DLL_API void blsGetPublicKey(blsPublicKey *pub, const blsSecretKey *sec);
 
diff --git a/src/bls_c_impl.hpp b/src/bls_c_impl.hpp
index 197c146..b38c1ad 100644
--- a/src/bls_c_impl.hpp
+++ b/src/bls_c_impl.hpp
@@ -163,6 +163,12 @@ int blsSecretKeySetLittleEndian(blsSecretKey *sec, const void *buf, mclSize bufS
 	cast(&sec->v)->setArrayMask((const char *)buf, bufSize);
 	return 0;
 }
+int blsSecretKeySetLittleEndianMod(blsSecretKey *sec, const void *buf, mclSize bufSize)
+{
+	bool b;
+	cast(&sec->v)->setArray(&b, (const char *)buf, bufSize, mcl::fp::Mod);
+	return b ? 0 : -1;
+}
 
 void blsGetPublicKey(blsPublicKey *pub, const blsSecretKey *sec)
 {
diff --git a/test/bls_c_test.hpp b/test/bls_c_test.hpp
index cb5c912..b058e6c 100644
--- a/test/bls_c_test.hpp
+++ b/test/bls_c_test.hpp
@@ -3,6 +3,7 @@
 #include <bls/bls.h>
 #include <string.h>
 #include <cybozu/benchmark.hpp>
+#include <gmpxx.h>
 
 size_t pubSize(size_t FrSize)
 {
@@ -78,7 +79,7 @@ void blsDataTest()
 	CYBOZU_TEST_ASSERT(blsSignatureIsEqual(&sig1, &sig2));
 }
 
-void blsOrderTest(const char *curveOrder, const char *fieldOrder)
+void blsOrderTest(const char *curveOrder/*Fr*/, const char *fieldOrder/*Fp*/)
 {
 	char buf[1024];
 	size_t len;
@@ -350,6 +351,30 @@ void blsTrivialShareTest()
 	CYBOZU_TEST_ASSERT(blsPublicKeyIsEqual(&pub1, &pub2));
 }
 
+void modTest(const char *rStr)
+{
+	std::cout << std::hex;
+	unsigned char buf[1024] = {};
+	int ret;
+	blsSecretKey sec;
+	const size_t pos = 63;
+	buf[pos] = 0xff;
+	mpz_class x = mpz_class(buf[pos]) << (pos * 8);
+	ret = blsSecretKeySetLittleEndianMod(&sec, buf, pos + 1);
+	CYBOZU_TEST_EQUAL(ret, 0);
+	mpz_class r(rStr);
+	x %= r;
+	size_t n = blsSecretKeySerialize(buf, sizeof(buf), &sec);
+	CYBOZU_TEST_ASSERT(n > 0);
+	// serialized data to mpz_class
+	mpz_class y = 0;
+	for (size_t i = 0; i < n; i++) {
+		y <<= 8;
+		y += buf[n - 1 - i];
+	}
+	CYBOZU_TEST_EQUAL(x, y);
+}
+
 void blsBench()
 {
 	blsSecretKey sec;
@@ -370,8 +395,8 @@ CYBOZU_TEST_AUTO(all)
 {
 	const struct {
 		int curveType;
-		const char *p;
 		const char *r;
+		const char *p;
 	} tbl[] = {
 		{
 			MCL_BN254,
@@ -403,11 +428,12 @@ CYBOZU_TEST_AUTO(all)
 		}
 		bls_use_stackTest();
 		blsDataTest();
-		blsOrderTest(tbl[i].p, tbl[i].r);
+		blsOrderTest(tbl[i].r, tbl[i].p);
 		blsSerializeTest();
 		if (tbl[i].curveType == MCL_BLS12_381) blsVerifyOrderTest();
 		blsAddSubTest();
 		blsTrivialShareTest();
+		modTest(tbl[i].r);
 		blsBench();
 	}
 }