diff --git a/Implementierung/lib/md2.h b/Implementierung/lib/md2.h
index 5fe72ab..bcaa038 100644
--- a/Implementierung/lib/md2.h
+++ b/Implementierung/lib/md2.h
@@ -10,7 +10,6 @@
 
 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);
 
 /**
  * @brief Calculates checksum of buf and stores it in out
@@ -21,15 +20,6 @@ typedef void (*md2_checksum_func)(size_t len, uint8_t* buf);
  */
 extern md2_hash_func md2_hash;
 
-/**
- * @brief Calculates checksum of buf and appends it to buf
- *
- * @param len Length of data which the checksum should be calculated of
- * @param buf Location of the data. Make sure to reserve 16 bytes more so the
- * chechsum fits!
- */
-extern md2_checksum_func md2_checksum;
-
 /**
  * @brief Choose the implementation to use
  *
diff --git a/Implementierung/lib/md2_impls/md2_0.h b/Implementierung/lib/md2_impls/md2_0.h
index 5bb2df7..cc3a7d4 100644
--- a/Implementierung/lib/md2_impls/md2_0.h
+++ b/Implementierung/lib/md2_impls/md2_0.h
@@ -9,6 +9,5 @@
 #include <sys/types.h>
 
 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/lib/md2_impls/md2_1.h b/Implementierung/lib/md2_impls/md2_1.h
index e6abb93..1473fbb 100644
--- a/Implementierung/lib/md2_impls/md2_1.h
+++ b/Implementierung/lib/md2_impls/md2_1.h
@@ -9,6 +9,5 @@
 #include <sys/types.h>
 
 void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16]);
-void md2_checksum_1(size_t len, uint8_t* buf);
 
 #endif  // MD2_1_H
\ No newline at end of file
diff --git a/Implementierung/lib/md2_impls/md2_common.h b/Implementierung/lib/md2_impls/md2_common.h
index dad4801..663c0d4 100644
--- a/Implementierung/lib/md2_impls/md2_common.h
+++ b/Implementierung/lib/md2_impls/md2_common.h
@@ -59,8 +59,73 @@ extern unsigned char MD2_PI_SUBST[256];
  */
 void md2_print_buf(size_t len, uint8_t buf[len]);
 
+/**
+ * @brief Calculates checksum of buf and appends it to buf
+ *
+ * @param len Length of data which the checksum should be calculated of
+ * @param buf Location of the data. Make sure to reserve 16 bytes more so the
+ * chechsum fits!
+ */
+void md2_checksum(size_t len, uint8_t* buf);
+
+/**
+ * @brief Calculates checksum of buf and writes it into a target
+ *
+ * @param len Length of data which the checksum should be calculated of
+ * @param buf Location of the data. Make sure to reserve 16 bytes more so the
+ * chechsum fits!
+ * @param checksum the output checksum
+ */
+void md2_checksum_with_target(size_t len, const uint8_t* buf,
+                              uint8_t checksum[16]);
+
+/**
+ * @brief Process one block of the checksum
+ *
+ * @param block the block to process
+ * @param checksum the output checksum
+ * @param l the current l
+ */
+void md2_process_block_checksum(uint8_t const block[16], uint8_t checksum[16],
+                                uint8_t* l);
+
+/**
+ * @brief Stores the time if start of a step, calculates the duration if end
+ *
+ * @param step the step to process
+ */
 void md2_process_detailed_benchmark_step(enum md2_detailed_benchmark_step step);
 
+/**
+ * @brief Print the detailed benchmark result
+ *
+ */
 void md2_print_detailed_benchmark_result();
 
+/**
+ * @brief Add padding and allocate extra space for the checksum
+ *
+ * @param buf buffer of the whole message
+ * @param len length of buf
+ * @return uint8_t* pointer to the new buffer
+ */
+uint8_t* md2_add_padding_and_space_for_checksum(const uint8_t* buf,
+                                                size_t* len);
+
+/**
+ * @brief The second loop of the md2 algorithm
+ *
+ * @param messageDigestBuf the message digest buffer
+ */
+void md2_second_loop(uint8_t* messageDigestBuf);
+
+/**
+ * @brief The first loop of the md2 algorithm
+ *
+ * @param buf buffer of the whole message
+ * @param messageDigestBuf the message digest buffer
+ * @param i the index of the 16-byte message block
+ */
+void md2_first_loop(const uint8_t* buf, uint8_t* messageDigestBuf, int i);
+
 #endif  // MD2_COMMON_H
\ No newline at end of file
diff --git a/Implementierung/src/md2.c b/Implementierung/src/md2.c
index 9965047..75cc1ba 100644
--- a/Implementierung/src/md2.c
+++ b/Implementierung/src/md2.c
@@ -8,11 +8,13 @@
 #include "../lib/md2_impls/md2_reference/md2_reference.h"
 
 md2_hash_func md2_hash;
-md2_checksum_func md2_checksum;
 
 // The file "testfile" should lead to this hash:
 // fc982e558db259f298b43cd4c1241c66
 
+static md2_hash_func md2_implementations[] = {
+    md2_hash_0, md2_hash_1, md2_hash_2, md2_hash_3, md2_hash_ref};
+
 void md2_encode_hash(uint8_t hash[16], char* string_hash) {
   for (int i = 0; i < 16; i++) {
     sprintf(string_hash + (2 * i), "%02x", hash[i]);
@@ -20,33 +22,7 @@ void md2_encode_hash(uint8_t hash[16], char* string_hash) {
 }
 
 bool md2_choose_implementation(int i) {
-  switch (i) {
-    case 0:
-      md2_hash = md2_hash_0;
-      md2_checksum = md2_checksum_0;
-      return true;
-
-    case 1:
-      md2_hash = md2_hash_1;
-      md2_checksum = md2_checksum_1;
-      return true;
-
-    case 2:
-      md2_hash = md2_hash_2;
-      md2_checksum = NULL;
-      return true;
-
-    case 3:
-      md2_hash = md2_hash_3;
-      md2_checksum = NULL;
-      return true;
-
-    case 4:
-      md2_hash = md2_hash_ref;
-      md2_checksum = NULL;
-      return true;
-
-    default:
-      return false;
-  }
+  if (i < 0 || i > 4) return false;
+  md2_hash = md2_implementations[i];
+  return true;
 }
\ 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 fa645b8..ce53693 100644
--- a/Implementierung/src/md2_impls/md2_0.c
+++ b/Implementierung/src/md2_impls/md2_0.c
@@ -2,50 +2,15 @@
 
 #include "../../lib/md2_impls/md2_common.h"
 
-void md2_checksum_0(size_t len, uint8_t* buf) {
-  uint8_t l = 0;
-
-  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:
-      buf[len + j] ^= MD2_PI_SUBST[c ^ l];
-      l = buf[len + j];
-    }
-  }
-}
-
 void md2_hash_0(size_t len, const uint8_t buf[len], uint8_t out[16]) {
   // === step 1 ===
-  int paddingNeeded = 16 - (len % 16);
-  uint8_t originalPadding = paddingNeeded;
-  len += paddingNeeded;
-
-  // printf("len: %d\n", len);
-
-  // +16 for the checksum
-  uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
+  uint8_t* newBuf = md2_add_padding_and_space_for_checksum(buf, &len);
   if (newBuf == NULL) {
     return;
   }
-  memcpy(newBuf, buf, len - paddingNeeded);
-
-  // printBuf(len + 16, newBuf);
-
-  while (paddingNeeded > 0) {
-    newBuf[len - paddingNeeded] = originalPadding;
-    paddingNeeded--;
-  }
-  // printf("buf with padding: ");
-  // printBuf(len + 16, newBuf);
 
   // === step 2 ===
-  CHECKSUM_START_MARK
-  md2_checksum_0(len, newBuf);
-  CHECKSUM_END_MARK
-
-  // printf("buf with cecksum: ");
-  // printBuf(len + 16, newBuf);
+  md2_checksum(len, newBuf);
 
   // === step 3 ===
   uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
@@ -54,29 +19,11 @@ 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 (size_t i = 0; i <= (len + 16) / 16 - 1; i++) {
-    FIRST_LOOP_START_MARK
-    for (int j = 0; j < 16; j++) {
-      messageDigestBuf[16 + j] = newBuf[i * 16 + j];
-      messageDigestBuf[32 + j] =
-          (messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
-    }
-    FIRST_LOOP_END_MARK
-
-    u_int8_t t = 0;
-
-    SECOND_LOOP_START_MARK
-    for (int j = 0; j < 18; j++) {
-      for (int k = 0; k < 48; k++) {
-        t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
-      }
-      t = (t + j) % 256;
-    }
-    SECOND_LOOP_END_MARK
+  // <= because we need to hash the last block (the checksum) too
+  for (size_t i = 0; i <= (len) / 16; i++) {
+    md2_first_loop(newBuf, messageDigestBuf, i);
+    md2_second_loop(messageDigestBuf);
   }
-  // printf("messageDigestBuf: \n");
-  // printBuf(16, messageDigestBuf);
 
   END_MARK
   memcpy(out, messageDigestBuf, 16);
diff --git a/Implementierung/src/md2_impls/md2_1.c b/Implementierung/src/md2_impls/md2_1.c
index 924282c..57dbd22 100644
--- a/Implementierung/src/md2_impls/md2_1.c
+++ b/Implementierung/src/md2_impls/md2_1.c
@@ -4,19 +4,6 @@
 
 #include "../../lib/md2_impls/md2_common.h"
 
-void md2_checksum_1(size_t len, uint8_t *buf) {
-  uint8_t l = 0;
-
-  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:
-      buf[len + j] ^= MD2_PI_SUBST[c ^ l];
-      l = buf[len + j];
-    }
-  }
-}
-
 static uint8_t PADDING[17][16] = {
     {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
     {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
@@ -55,9 +42,7 @@ void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16]) {
   memcpy(newBuf + len - paddingNeeded, PADDING + paddingNeeded, paddingNeeded);
 
   // === step 2 ===
-  CHECKSUM_START_MARK
-  md2_checksum_1(len, newBuf);
-  CHECKSUM_END_MARK
+  md2_checksum(len, newBuf);
 
   // === step 3 ===
   uint8_t *messageDigestBuf = aligned_alloc(16, sizeof(uint8_t) * 48);
@@ -81,16 +66,7 @@ void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16]) {
     _mm_store_si128((__m128i *)(messageDigestBuf + 32), vy);
     FIRST_LOOP_END_MARK
 
-    u_int8_t t = 0;
-
-    SECOND_LOOP_START_MARK
-    for (int j = 0; j < 18; j++) {
-      for (int k = 0; k < 48; k++) {
-        t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
-      }
-      t = (t + j) & 255;
-    }
-    SECOND_LOOP_END_MARK
+    md2_second_loop(messageDigestBuf);
   }
 
   END_MARK
diff --git a/Implementierung/src/md2_impls/md2_2.c b/Implementierung/src/md2_impls/md2_2.c
index be602f2..c359da5 100644
--- a/Implementierung/src/md2_impls/md2_2.c
+++ b/Implementierung/src/md2_impls/md2_2.c
@@ -3,32 +3,8 @@
 #include "../../lib/md2_impls/md2_common.h"
 
 void process_block_hash(uint8_t block[16], uint8_t messageDigestBuf[48]) {
-  FIRST_LOOP_START_MARK
-  for (int j = 0; j < 16; j++) {
-    messageDigestBuf[16 + j] = block[j];
-    messageDigestBuf[32 + j] = (messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
-  }
-  FIRST_LOOP_END_MARK
-
-  u_int8_t t = 0;
-
-  SECOND_LOOP_START_MARK
-  for (int j = 0; j < 18; j++) {
-    for (int k = 0; k < 48; k++) {
-      t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
-    }
-    t = (t + j) % 256;
-  }
-  SECOND_LOOP_END_MARK
-}
-
-void process_block_checksum(uint8_t block[16], uint8_t checksum[16],
-                            uint8_t* l) {
-  for (int j = 0; j < 16; j++) {
-    u_int8_t c = block[j];
-    // reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
-    (*l) = checksum[j] ^= MD2_PI_SUBST[c ^ (*l)];
-  }
+  md2_first_loop(block, messageDigestBuf, 0);
+  md2_second_loop(messageDigestBuf);
 }
 
 void apply_padding(size_t len, uint8_t buf[16]) {
@@ -79,7 +55,7 @@ void md2_hash_2(size_t len, const uint8_t buf[len], uint8_t out[16]) {
     }
 
     CHECKSUM_START_MARK
-    process_block_checksum(data, checksum, &l);
+    md2_process_block_checksum(data, checksum, &l);
     CHECKSUM_END_MARK
     process_block_hash(data, messageDigestBuf);
 
@@ -87,7 +63,7 @@ void md2_hash_2(size_t len, const uint8_t buf[len], uint8_t out[16]) {
   };
 
   apply_padding(bytes_left_to_process % 16, data);
-  process_block_checksum(data, checksum, &l);
+  md2_process_block_checksum(data, checksum, &l);
   process_block_hash(data, messageDigestBuf);
 
   process_block_hash(checksum, messageDigestBuf);
diff --git a/Implementierung/src/md2_impls/md2_3.c b/Implementierung/src/md2_impls/md2_3.c
index a8d13f3..160c2fe 100644
--- a/Implementierung/src/md2_impls/md2_3.c
+++ b/Implementierung/src/md2_impls/md2_3.c
@@ -10,24 +10,8 @@ struct thread_args {
 void process_nothread_hash(size_t len, const uint8_t buf[len],
                            uint8_t messageDigestBuf[48]) {
   for (size_t i = 0; i < (len + 16) / 16 - 1; i++) {
-    FIRST_LOOP_START_MARK
-    for (int j = 0; j < 16; j++) {
-      messageDigestBuf[16 + j] = buf[i * 16 + j];
-      messageDigestBuf[32 + j] =
-          (messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
-    }
-    FIRST_LOOP_END_MARK
-
-    u_int8_t t = 0;
-
-    SECOND_LOOP_START_MARK
-    for (int j = 0; j < 18; j++) {
-      for (int k = 0; k < 48; k++) {
-        t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
-      }
-      t = (t + j) % 256;
-    }
-    SECOND_LOOP_END_MARK
+    md2_first_loop(buf, messageDigestBuf, i);
+    md2_second_loop(messageDigestBuf);
   }
 }
 
@@ -51,36 +35,16 @@ void* process_checksum(void* threasdArgs) {
     return NULL;
   }
 
-  uint8_t l = 0;
-  CHECKSUM_START_MARK
-  for (size_t i = 0; i < args->len / 16; i++) {
-    for (int j = 0; j < 16; j++) {
-      u_int8_t c = args->buf[i * 16 + j];
-      // reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
-      l = checksum[j] ^= MD2_PI_SUBST[c ^ l];
-    }
-  }
-  CHECKSUM_END_MARK
+  md2_checksum_with_target(args->len, args->buf, checksum);
   pthread_exit(checksum);
 }
 
 void md2_hash_3(size_t len, const uint8_t buf[len], uint8_t out[16]) {
-  int paddingNeeded = 16 - (len % 16);
-  uint8_t originalPadding = paddingNeeded;
-  len += paddingNeeded;
-
-  uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
+  uint8_t* newBuf = md2_add_padding_and_space_for_checksum(buf, &len);
   if (newBuf == NULL) {
     return;
   }
 
-  memcpy(newBuf, buf, len - paddingNeeded);
-
-  while (paddingNeeded > 0) {
-    newBuf[len - paddingNeeded] = originalPadding;
-    paddingNeeded--;
-  }
-
   pthread_t thread_1, thread_2;
 
   struct thread_args thread_args = {len, newBuf};
diff --git a/Implementierung/src/md2_impls/md2_common.c b/Implementierung/src/md2_impls/md2_common.c
index 963c4d4..7128922 100644
--- a/Implementierung/src/md2_impls/md2_common.c
+++ b/Implementierung/src/md2_impls/md2_common.c
@@ -57,4 +57,71 @@ void md2_print_detailed_benchmark_result() {
   printf("  First loop: %f\n", detailed_benchmark_times[1]);
   printf("  Second loop: %f\n", detailed_benchmark_times[2]);
   printf("\n");
+}
+
+uint8_t* md2_add_padding_and_space_for_checksum(const uint8_t* buf,
+                                                size_t* len) {
+  int paddingNeeded = 16 - ((*len) % 16);
+  uint8_t originalPadding = paddingNeeded;
+  (*len) += paddingNeeded;
+
+  // +16 for the checksum
+  uint8_t* newBuf = calloc((*len) + 16, sizeof(uint8_t));
+  if (newBuf == NULL) {
+    return NULL;
+  }
+  memcpy(newBuf, buf, (*len) - paddingNeeded);
+
+  while (paddingNeeded > 0) {
+    newBuf[(*len) - paddingNeeded] = originalPadding;
+    paddingNeeded--;
+  }
+
+  return newBuf;
+}
+
+void md2_process_block_checksum(uint8_t const block[16], uint8_t checksum[16],
+                                uint8_t* l) {
+  for (int j = 0; j < 16; j++) {
+    u_int8_t c = block[j];
+    // reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
+    (*l) = checksum[j] ^= MD2_PI_SUBST[c ^ (*l)];
+  }
+}
+
+void md2_checksum(size_t len, uint8_t* buf) {
+  md2_checksum_with_target(len, buf, buf + len);
+}
+
+void md2_checksum_with_target(size_t len, const uint8_t* buf,
+                              uint8_t checksum[16]) {
+  CHECKSUM_START_MARK
+  uint8_t l = 0;
+
+  for (size_t i = 0; i < len / 16; i++) {
+    md2_process_block_checksum(buf + i * 16, checksum, &l);
+  }
+  CHECKSUM_END_MARK
+}
+
+void md2_second_loop(uint8_t* messageDigestBuf) {
+  u_int8_t t = 0;
+
+  SECOND_LOOP_START_MARK
+  for (int j = 0; j < 18; j++) {
+    for (int k = 0; k < 48; k++) {
+      t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
+    }
+    t = (t + j) & 255;
+  }
+  SECOND_LOOP_END_MARK
+}
+
+void md2_first_loop(const uint8_t* buf, uint8_t* messageDigestBuf, int i) {
+  FIRST_LOOP_START_MARK
+  for (int j = 0; j < 16; j++) {
+    messageDigestBuf[16 + j] = buf[i * 16 + j];
+    messageDigestBuf[32 + j] = (messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
+  }
+  FIRST_LOOP_END_MARK
 }
\ No newline at end of file