diff --git a/Implementierung/lib/md2_impls/md2_1.h b/Implementierung/lib/md2_impls/md2_1.h
new file mode 100644
index 0000000..8777277
--- /dev/null
+++ b/Implementierung/lib/md2_impls/md2_1.h
@@ -0,0 +1,23 @@
+#ifndef MD2_1_H
+#define MD2_1_H
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "../io.h"
+
+/**
+ * @brief This implementation optimizes small operations and uses SIMD
+ *
+ * @param _ unused
+ * @param filename name of the file to load
+ * @param out
+ */
+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
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diff --git a/Implementierung/src/md2_impls/md2_1.c b/Implementierung/src/md2_impls/md2_1.c
new file mode 100644
index 0000000..6e997ed
--- /dev/null
+++ b/Implementierung/src/md2_impls/md2_1.c
@@ -0,0 +1,75 @@
+#include "../../lib/md2_impls/md2_1.h"
+
+#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];
+    }
+  }
+}
+
+void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16]) {
+  // === step 1 ===
+  int paddingNeeded = 16 - (len & 7);
+  uint8_t originalPadding = paddingNeeded;
+  len += paddingNeeded;
+
+  // printf("len: %d\n", len);
+
+  // +16 for the checksum
+  uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
+  // TODO: null check
+  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 ===
+  md2_checksum_1(len, newBuf);
+
+  // printf("buf with cecksum: ");
+  // printBuf(len + 16, newBuf);
+
+  // === step 3 ===
+  uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
+  // TODO: add null check
+
+  // === step 4 ===
+  // <= because we need to hash the last block too
+  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] =
+          (messageDigestBuf[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] ^ MD2_PI_SUBST[t];
+      }
+      t = (t + j) & 127;
+    }
+  }
+  // printf("messageDigestBuf: \n");
+  // printBuf(16, messageDigestBuf);
+
+  memcpy(out, messageDigestBuf, 16);
+
+  free(messageDigestBuf);
+  free(newBuf);
+}
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