add test of N=2

test/mont_fp_test.cpp

@@ -321,9 +321,16 @@ struct Test {
 
 	void conv()
 	{
-		const char *bin = "0b100100011010001010110011110001001000000010010001101000101011001111000100100000001001000110100010101100111100010010000";
-		const char *hex = "0x123456789012345678901234567890";
-		const char *dec = "94522879687365475552814062743484560";
+		const char *bin, *hex, *dec;
+		if (Fp::getBitSize() <= 117) {
+			bin = "0b10000000000000000000000000000000000000000000000000000000000001110";
+			hex = "0x1000000000000000e";
+			dec = "18446744073709551630";
+		} else {
+			bin = "0b100100011010001010110011110001001000000010010001101000101011001111000100100000001001000110100010101100111100010010000";
+			hex = "0x123456789012345678901234567890";
+			dec = "94522879687365475552814062743484560";
+		}
 		Fp b(bin);
 		Fp h(hex);
 		Fp d(dec);
@@ -623,6 +630,12 @@ CYBOZU_TEST_AUTO(test)
 {
 	Test test;
 	const char *tbl[] = {
+		// N = 2
+		"0x0000000000000001000000000000000d",
+		"0x7fffffffffffffffffffffffffffffff",
+		"0x8000000000000000000000000000001d",
+		"0xffffffffffffffffffffffffffffff61",
+
 		// N = 3
 		"0x000000000000000100000000000000000000000000000033", // min prime
 		"0x00000000fffffffffffffffffffffffffffffffeffffac73",