diff --git a/Implementierung/src/io.c b/Implementierung/src/io.c
index 339bd75..048aee7 100644
--- a/Implementierung/src/io.c
+++ b/Implementierung/src/io.c
@@ -34,6 +34,10 @@ uint8_t* read_file(const char* path, size_t* size) {
   }
 
   uint8_t* data = malloc(statOfFile.st_size);
+  if (data == NULL) {
+    printf("Failure: malloc returns NULL");
+    return -1;
+  }
 
   size_t bytesRead =
       fread(data, statOfFile.st_blksize, statOfFile.st_blocks, f);
diff --git a/Implementierung/src/md2_impls/md2_0.c b/Implementierung/src/md2_impls/md2_0.c
index eeb4354..c344325 100644
--- a/Implementierung/src/md2_impls/md2_0.c
+++ b/Implementierung/src/md2_impls/md2_0.c
@@ -25,7 +25,10 @@ void md2_hash_0(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
   // +16 for the checksum
   uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
-  // TODO: null check
+  if (newBuf == NULL) {
+    printf("Failure: calloc returns NULL");
+    return -1;
+  }
   memcpy(newBuf, buf, len - paddingNeeded);
 
   // printBuf(len + 16, newBuf);
@@ -45,7 +48,11 @@ void md2_hash_0(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
   // === step 3 ===
   uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
-  // TODO: add null check
+  if (messageDigestBuf == NULL) {
+    printf("Failure: calloc returns NULL");
+    return -1;
+  }
+
 
   // === step 4 ===
   // <= because we need to hash the last block too
diff --git a/Implementierung/src/md2_impls/md2_1.c b/Implementierung/src/md2_impls/md2_1.c
index d4e2943..ff2f1ff 100644
--- a/Implementierung/src/md2_impls/md2_1.c
+++ b/Implementierung/src/md2_impls/md2_1.c
@@ -45,74 +45,45 @@ void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16])
   int paddingNeeded = 16 - (len & 15);
   len += paddingNeeded;
 
-  // printf("len: %d\n", len);
-
-  // +16 for the checksum
   uint8_t* newBuf = aligned_alloc(16, sizeof(uint8_t)*(len + 16));
+  if (newBuf == NULL) {
+    printf("Failure: aligned_alloc returns NULL");
+    return -1;
+  }
 
   for(size_t i = 0; i < 16; i++) {
     newBuf[len + i] = 0;
   }
-  
-  // uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
-  // TODO: null check
+
   memcpy(newBuf, buf, len - paddingNeeded);
 
-  //md2_print_buf(len + 16, newBuf);
-
   memcpy(newBuf + len - paddingNeeded, PADDING + paddingNeeded, paddingNeeded);
 
-  // printf("buf with padding: ");
-  //md2_print_buf(len + 16, newBuf);
-
   // === step 2 ===
   md2_checksum_1(len, newBuf);
 
-  // printf("buf with cecksum: ");
-  // printBuf(len + 16, newBuf);
-
   // === step 3 ===
   uint8_t *messageDigestBuf = aligned_alloc(16, sizeof(uint8_t) * 48);
-  // TODO: add null check
+  if (messageDigestBuf == NULL) {
+    printf("Failure: aligned_alloc returns NULL");
+    return -1;
+  }
+
   for (size_t i = 0; i < 48; i++) {
     messageDigestBuf[i] = 0;
   }
 
   // === step 4 ===
-  // <= because we need to hash the last block too
   __m128i vx;
   __m128i vy;
   for (size_t i = 0; i <= (len + 16) / 16 - 1; i++)
   {
-    
     vx = _mm_load_si128((__m128i*) (newBuf + i * 16));
     _mm_store_si128((__m128i*) (messageDigestBuf + 16), vx);
     vy = _mm_load_si128((__m128i*) (messageDigestBuf));
     vy = _mm_xor_si128(vy, vx);
     _mm_store_si128((__m128i*) (messageDigestBuf + 32), vy);
-    
-    
-    /*
-    for (int j = 0; j < 16; j++)
-    {
-      //messageDigestBuf[16 + j] = newBuf[i * 16 + j];
-      messageDigestBuf[32 + j] =
-          (messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
-    }
-    /*
-    vy = _mm_load_si128((__m128i*) (messageDigestBuf));
-    _mm_xor_si128(vy, vx);
-    _mm_store_si128((__m128i*) messageDigestBuf, vy);
-    md2_print_buf(48, messageDigestBuf);
-    md2_print_buf(len + 16, newBuf);
-    /*
-    printf("newBuf: erstes Element:");
-    printf(*(newBuf + i * 16));
-    printf("mdb:");
-    printf(*(messageDigestBuf + 16));
-    */
-    
-    
+  
 
     u_int8_t t = 0;
 
@@ -125,8 +96,6 @@ void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16])
       t = (t + j) & 255;
     }
   }
-  // printf("messageDigestBuf: \n");
-  // printBuf(16, messageDigestBuf);
 
   memcpy(out, messageDigestBuf, 16);
 
diff --git a/Implementierung/src/md2_impls/md2_2.c b/Implementierung/src/md2_impls/md2_2.c
index 1349c0f..b0955ba 100644
--- a/Implementierung/src/md2_impls/md2_2.c
+++ b/Implementierung/src/md2_impls/md2_2.c
@@ -50,12 +50,24 @@ void md2_hash_2(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
   // === step 3 ===
   uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
+  if (messageDigestBuf == NULL) {
+    printf("Failure: calloc returns NULL");
+    return -1;
+  }
 
   // === step 4 ===
   uint8_t l = 0;
   uint8_t* checksum = calloc(16, sizeof(uint8_t));
+  if (checksum == NULL) {
+    printf("Failure: calloc returns NULL");
+    return -1;
+  }
 
   uint8_t* data = malloc(16);
+  if (data == NULL) {
+    printf("Failure: malloc returns NULL");
+    return -1;
+  }
   size_t bytes_left_to_read = file_stat.st_size;
   size_t bytes_left_to_process = 0;