diff --git a/generator.cpp b/generator.cpp
index 5393f70..0ff0e21 100644
--- a/generator.cpp
+++ b/generator.cpp
@@ -1,5 +1,6 @@
 #include <cmath>
 #include <cassert>
+#include <cstdint>
 #include <stdexcept>
 #include <tuple>
 #include "generator.h"
@@ -7,7 +8,7 @@
 using namespace std;
 
 struct G_state{
-	long k;
+	int64_t k;
 	unsigned __int128 ctr;
 };
 
@@ -18,7 +19,7 @@ G_state *initialize_generator(){
 	return G;
 };
 
-string do_crypto(long k, unsigned __int128 ctr){
+string do_crypto(int64_t k, unsigned __int128 ctr){
 	/* this function calls the block cipher
 	 * returns a string of k*(16 bytes);
 	   do whatever atm */
diff --git a/generator.h b/generator.h
index 53304e7..2c5712c 100644
--- a/generator.h
+++ b/generator.h
@@ -10,7 +10,7 @@ struct G_state;
 /* initializes generator */
 G_state *initialize_generator();
 
-std::string do_crypto(long k, unsigned __int128 ctr);
+std::string do_crypto(int64_t k, unsigned __int128 ctr);
 
 std::tuple<std::string, G_state> generate_blocks(G_state G, int k_blocks);