diff --git a/client/Makefile b/client/Makefile
index c42a097..90a2b15 100644
--- a/client/Makefile
+++ b/client/Makefile
@@ -1,5 +1,20 @@
-d4:	d4.o others/hmac/sha2.o others/hmac/hmac.o
-	gcc -Wall -o d4 d4.o others/hmac/hmac.o others/hmac/sha2.o -luuid
+all: d4
+
+
+hmac: hmac.o sha2.o
+	$(CC) sha2.o hmac.o -o hmac
+
+hmac.o: ./others/hmac/hmac_sha2.c ./others/hmac/hmac_sha2.h
+	$(CC) -Wall -c ./others/hmac/hmac_sha2.c -o hmac.o
+
+sha2.o: ./others/hmac/sha2.c ./others/hmac/sha2.h
+	$(CC) -c ./others/hmac/sha2.c -o sha2.o
+
+clean:
+	- rm -rf *.o hmac
+
+d4:	d4.o sha2.o hmac.o
+	gcc -Wall -o d4 d4.o hmac.o sha2.o -luuid
 
 d4.o:	d4.c
 	gcc -Wall -c d4.c
diff --git a/client/others/hmac b/client/others/hmac
new file mode 160000
index 0000000..5efc450
--- /dev/null
+++ b/client/others/hmac
@@ -0,0 +1 @@
+Subproject commit 5efc450f9dd204059b2f29808deaf2f8239b8129