diff --git a/Implementierung/lib/helper.h b/Implementierung/lib/helper.h
index 410940b..90ddbc4 100644
--- a/Implementierung/lib/helper.h
+++ b/Implementierung/lib/helper.h
@@ -2,10 +2,10 @@
 #define HELPER_H
 
 #include <errno.h>
-#include <stdint.h>
-#include <stdlib.h>
-#include <stdio.h>
 #include <getopt.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
 
 enum argumentParseResult {
   RESULT_OK = 0,
@@ -14,12 +14,21 @@ enum argumentParseResult {
 };
 
 struct configuration {
-    char* filename;
+  char* filename;
   int implementationToUse;
   int doBenchmark;
   int benchmarkingCycles;
 };
 
-enum argumentParseResult parseArguments(int argc, char** argv, struct configuration* c);
+/**
+ * @brief parse commandline arguments to config and print errors, if any
+ *
+ * @param argc argc
+ * @param argv argv
+ * @param c pointer where the configuration should be stored
+ * @return enum argumentParseResult
+ */
+enum argumentParseResult parseArguments(int argc, char** argv,
+                                        struct configuration* c);
 
-#endif // HELPER_H
\ No newline at end of file
+#endif  // HELPER_H
\ No newline at end of file
diff --git a/Implementierung/lib/io.h b/Implementierung/lib/io.h
index a57a141..6082117 100644
--- a/Implementierung/lib/io.h
+++ b/Implementierung/lib/io.h
@@ -7,4 +7,13 @@
 #include <stdlib.h>
 #include <sys/stat.h>
 
-#endif // IO_H
\ No newline at end of file
+/**
+ * @brief reads a file at a path
+ * 
+ * @param path the filepath
+ * @param size a pointer where the size of the result should be stored
+ * @return the raw data
+ */
+static uint8_t* read_file(const char* path, size_t* size);
+
+#endif  // IO_H
\ No newline at end of file
diff --git a/Implementierung/lib/md2.h b/Implementierung/lib/md2.h
index 0a972e7..356980f 100644
--- a/Implementierung/lib/md2.h
+++ b/Implementierung/lib/md2.h
@@ -2,5 +2,23 @@
 #define MD2_H
 
 #include <stdint.h>
+#include <sys/types.h>
+
+/**
+ * @brief Calculates checksum of buf and stores it in out
+ * 
+ * @param len Length of the data at buf
+ * @param buf Location of the data
+ * @param out Destination array of for the checksum
+ */
+void md2_hash(size_t len, const uint8_t buf[], uint8_t out[16]);
+
+/**
+ * @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);
 
 #endif // MD2_H
\ No newline at end of file