diff --git a/lib/hmac.c b/lib/hmac.c
index a88ce410..c9b98069 100644
--- a/lib/hmac.c
+++ b/lib/hmac.c
@@ -33,6 +33,11 @@
 DECLARE_TEST_SUITE(hmac_test, "hmac functions test suite");
 #endif
 
+/**
+ * /brief populate the inner and outer pads
+ *
+ *
+ */
 static void
 pad_init(unsigned char *inner_pad, unsigned char *outer_pad,
         const unsigned char * const key, const int key_len)
@@ -56,8 +61,6 @@ pad_init(unsigned char *inner_pad, unsigned char *outer_pad,
     return;
 }
 
-/* Begin MD5 HMAC functions
-*/
 void
 hmac_md5(const char *msg, const unsigned int msg_len,
     unsigned char *hmac, const char *hmac_key, const int hmac_key_len)
@@ -101,8 +104,6 @@ hmac_md5(const char *msg, const unsigned int msg_len,
     return;
 }
 
-/* Begin SHA1 HMAC functions
-*/
 void
 hmac_sha1(const char *msg, const unsigned int msg_len,
     unsigned char *hmac, const char *hmac_key, const int hmac_key_len)
@@ -146,8 +147,6 @@ hmac_sha1(const char *msg, const unsigned int msg_len,
     return;
 }
 
-/* Begin SHA256 HMAC functions
-*/
 void
 hmac_sha256(const char *msg, const unsigned int msg_len,
     unsigned char *hmac, const char *hmac_key, const int hmac_key_len)
@@ -191,8 +190,6 @@ hmac_sha256(const char *msg, const unsigned int msg_len,
     return;
 }
 
-/* Begin SHA384 HMAC functions
-*/
 void
 hmac_sha384(const char *msg, const unsigned int msg_len,
     unsigned char *hmac, const char *hmac_key, const int hmac_key_len)
@@ -236,8 +233,6 @@ hmac_sha384(const char *msg, const unsigned int msg_len,
     return;
 }
 
-/* Begin SHA512 HMAC functions
-*/
 void
 hmac_sha512(const char *msg, const unsigned int msg_len,
     unsigned char *hmac, const char *hmac_key, const int hmac_key_len)
diff --git a/lib/hmac.h b/lib/hmac.h
index a5fb4785..9e81e36c 100644
--- a/lib/hmac.h
+++ b/lib/hmac.h
@@ -32,7 +32,7 @@
 
 #include "digest.h"
 
-#define MAX_DIGEST_BLOCK_LEN    SHA3_256_BLOCK_LEN
+#define MAX_DIGEST_BLOCK_LEN    SHA3_256_BLOCK_LEN /**< The longest block length is from SHA3_256 */
 /**
  * \brief Generate MD5 based HMAC
  *
@@ -47,16 +47,88 @@
  */
 void hmac_md5(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
+/**
+ * \brief Generate SHA1 based HMAC
+ *
+ * This function generates an HMAC verification hash, based on SHA1
+ *
+ * \param msg Pointer to the message to be signed
+ * \param msg_len size of the message string
+ * \param hmac Pointer to the hmac buffer, where the final hmac will be stored
+ * \param hmac_key Pointer to the key to be used for generating the hmac
+ * \param hmac_key_len Size of the hmac key
+ *
+ */
 void hmac_sha1(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
+/**
+ * \brief Generate SHA256 based HMAC
+ *
+ * This function generates an HMAC verification hash, based on SHA256
+ *
+ * \param msg Pointer to the message to be signed
+ * \param msg_len size of the message string
+ * \param hmac Pointer to the hmac buffer, where the final hmac will be stored
+ * \param hmac_key Pointer to the key to be used for generating the hmac
+ * \param hmac_key_len Size of the hmac key
+ *
+ */
 void hmac_sha256(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
+/**
+ * \brief Generate SHA384 based HMAC
+ *
+ * This function generates an HMAC verification hash, based on SHA384
+ *
+ * \param msg Pointer to the message to be signed
+ * \param msg_len size of the message string
+ * \param hmac Pointer to the hmac buffer, where the final hmac will be stored
+ * \param hmac_key Pointer to the key to be used for generating the hmac
+ * \param hmac_key_len Size of the hmac key
+ *
+ */
 void hmac_sha384(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
+/**
+ * \brief Generate SHA512 based HMAC
+ *
+ * This function generates an HMAC verification hash, based on SHA512
+ *
+ * \param msg Pointer to the message to be signed
+ * \param msg_len size of the message string
+ * \param hmac Pointer to the hmac buffer, where the final hmac will be stored
+ * \param hmac_key Pointer to the key to be used for generating the hmac
+ * \param hmac_key_len Size of the hmac key
+ *
+ */
 void hmac_sha512(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
+/**
+ * \brief Generate SHA3-256 based HMAC
+ *
+ * This function generates an HMAC verification hash, based on SHA3-256
+ *
+ * \param msg Pointer to the message to be signed
+ * \param msg_len size of the message string
+ * \param hmac Pointer to the hmac buffer, where the final hmac will be stored
+ * \param hmac_key Pointer to the key to be used for generating the hmac
+ * \param hmac_key_len Size of the hmac key
+ *
+ */
 void hmac_sha3_256(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
+/**
+ * \brief Generate SHA3-512 based HMAC
+ *
+ * This function generates an HMAC verification hash, based on SHA3-512
+ *
+ * \param msg Pointer to the message to be signed
+ * \param msg_len size of the message string
+ * \param hmac Pointer to the hmac buffer, where the final hmac will be stored
+ * \param hmac_key Pointer to the key to be used for generating the hmac
+ * \param hmac_key_len Size of the hmac key
+ *
+ */
 void hmac_sha3_512(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);