diff --git a/Implementierung/Makefile b/Implementierung/Makefile
index 5362c73..1c7ed9f 100644
--- a/Implementierung/Makefile
+++ b/Implementierung/Makefile
@@ -3,7 +3,7 @@
 SRC = src/main.c src/helper.c src/io.c src/md2.c src/md2_impls/md2_common.c src/md2_impls/md2_0.c
 OBJ = ${subst src,build,${SRC:.c=.o}}
 CC = gcc
-CFLAGS = -Ilib -ggdb -std=c11
+CFLAGS = -Ilib -ggdb -std=c11 -g -Wall -Wextra -no-pie -O3
 LDFLAGS = 
 
 all: md2
diff --git a/Implementierung/lib/md2.h b/Implementierung/lib/md2.h
index f0dc597..5fe72ab 100644
--- a/Implementierung/lib/md2.h
+++ b/Implementierung/lib/md2.h
@@ -8,7 +8,8 @@
 #include <string.h>
 #include <sys/types.h>
 
-typedef void (*md2_hash_func)(size_t len, const uint8_t buf[], uint8_t out[16]);
+typedef void (*md2_hash_func)(size_t len, const uint8_t buf[len],
+                              uint8_t out[16]);
 typedef void (*md2_checksum_func)(size_t len, uint8_t* buf);
 
 /**
diff --git a/Implementierung/lib/md2_impls/md2_0.h b/Implementierung/lib/md2_impls/md2_0.h
index 0b0172a..5bb2df7 100644
--- a/Implementierung/lib/md2_impls/md2_0.h
+++ b/Implementierung/lib/md2_impls/md2_0.h
@@ -8,7 +8,7 @@
 #include <string.h>
 #include <sys/types.h>
 
-void md2_hash_0(size_t len, const uint8_t buf[], uint8_t out[16]);
+void md2_hash_0(size_t len, const uint8_t buf[len], uint8_t out[16]);
 void md2_checksum_0(size_t len, uint8_t* buf);
 
 #endif  // MD2_0_H
\ No newline at end of file
diff --git a/Implementierung/src/md2_impls/md2_0.c b/Implementierung/src/md2_impls/md2_0.c
index 0bf59a6..eeb4354 100644
--- a/Implementierung/src/md2_impls/md2_0.c
+++ b/Implementierung/src/md2_impls/md2_0.c
@@ -5,7 +5,7 @@
 void md2_checksum_0(size_t len, uint8_t* buf) {
   uint8_t l = 0;
 
-  for (int i = 0; i < len / 16; i++) {
+  for (size_t i = 0; i < len / 16; i++) {
     for (int j = 0; j < 16; j++) {
       u_int8_t c = buf[i * 16 + j];
       // reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
@@ -49,7 +49,7 @@ void md2_hash_0(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
   // === step 4 ===
   // <= because we need to hash the last block too
-  for (int i = 0; i <= (len + 16) / 16 - 1; i++) {
+  for (size_t i = 0; i <= (len + 16) / 16 - 1; i++) {
     for (int j = 0; j < 16; j++) {
       messageDigestBuf[16 + j] = newBuf[i * 16 + j];
       messageDigestBuf[32 + j] =
diff --git a/Implementierung/src/md2_impls/md2_common.c b/Implementierung/src/md2_impls/md2_common.c
index 6d2598d..1fa9cb6 100644
--- a/Implementierung/src/md2_impls/md2_common.c
+++ b/Implementierung/src/md2_impls/md2_common.c
@@ -22,7 +22,7 @@ unsigned char MD2_PI_SUBST[256] = {
     20};
 
 void md2_print_buf(size_t len, uint8_t buf[len]) {
-  for (int i = 0; i < len; i++) {
+  for (size_t i = 0; i < len; i++) {
     printf("'%02x',", buf[i]);
   }
   printf("\n");