fix hash2rct in get_exponent

src/ringct/bulletproofs2.cc

@@ -109,7 +109,12 @@ static rct::key get_exponent(const rct::key &base, size_t idx)
 {
   static const std::string salt("bulletproof");
   std::string hashed = std::string((const char*)base.bytes, sizeof(base)) + salt + tools::get_varint_data(idx);
-  return rct::hashToPoint(rct::hash2rct(crypto::cn_fast_hash(hashed.data(), hashed.size())));
+  rct::key e;
+  ge_p3 e_p3;
+  rct::hash_to_p3(e_p3, rct::hash2rct(crypto::cn_fast_hash(hashed.data(), hashed.size())));
+  ge_p3_tobytes(e.bytes, &e_p3);
+  CHECK_AND_ASSERT_THROW_MES(!(e == rct::identity()), "Exponent is point at infinity");
+  return e;
 }
 
 static void init_exponents()