diff --git a/Implementierung/src/md2.c b/Implementierung/src/md2.c
index 1b3e0a3..bd21615 100644
--- a/Implementierung/src/md2.c
+++ b/Implementierung/src/md2.c
@@ -51,7 +51,7 @@ void md2_hash(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
   printf("len: %d\n", len);
 
-  uint8_t* newBuf = malloc(len + 16);  // 16 = Checksum
+  uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));  // +16 = Checksum
   memcpy(newBuf, buf, len - paddingNeeded);
   newBuf[4] = 'f';
 
@@ -65,5 +65,28 @@ void md2_hash(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
   printBuf(len + 16, newBuf);
 
+  // implement step 3
+  u_int8_t messageDigestBuf = calloc(48, sizeof(uint8_t));
+
+  for (int i = 0; i <= len / 16; i++) {  // <= because we need to hash the last block too
+    for (int j = 0; j < 16; j++) {
+      messageDigestBuf[16 + j] = newBuf[i * 16 + j];
+      messageDigestBuf[32 + j] = (newBuf[16 + j] ^ messageDigestBuf[j]);
+    }
+
+    u_int8_t t = 0;
+
+    for (int j = 0; j < 18; j++) {
+      for (int k = 0; k < 48; k++) {
+        t = messageDigestBuf[k] = messageDigestBuf[k] ^ PI_SUBST[t];
+      }
+      t = (t + j) % 256;
+    }
+  }
+  printf("messageDigestBuf: \n");
+  printBuf(16, messageDigestBuf);
+
+
+  free(messageDigestBuf);
   free(newBuf);
 }
\ No newline at end of file