diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index 8bcf766..e860de2 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -109,7 +109,7 @@
  * \brief           This function returns the message-digest information
  *                  associated with the given digest name.
  *
- * \param md_name   The name of the digest to search for.
+ * \param md_name   The name of the digest to search for. This must not be \c NULL.
  *
  * \return          The message-digest information associated with \p md_name.
  * \return          NULL if the associated message-digest information is not found.
@@ -120,7 +120,7 @@
  * \brief           This function returns the message-digest information
  *                  associated with the given digest type.
  *
- * \param md_type   The type of digest to search for.
+ * \param md_type   The type of digest to search for. This must not be \c NULL.
  *
  * \return          The message-digest information associated with \p md_type.
  * \return          NULL if the associated message-digest information is not found.
@@ -133,7 +133,7 @@
  *
  *                  This function should always be called first. It prepares the
  *                  context for mbedtls_md_setup() for binding it to a
- *                  message-digest algorithm.
+ *                  message-digest algorithm. The \p ctx must not be \c NULL.
  */
 void mbedtls_md_init( mbedtls_md_context_t *ctx );
 
@@ -148,7 +148,7 @@
  *                  Calling this function if you have previously
  *                  called mbedtls_md_init() and nothing else is optional.
  *                  You must not call this function if you have not called
- *                  mbedtls_md_init().
+ *                  mbedtls_md_init(). The \p ctx must not be \c NULL.
  */
 void mbedtls_md_free( mbedtls_md_context_t *ctx );
 
@@ -167,7 +167,7 @@
  *
  * \deprecated      Superseded by mbedtls_md_setup() in 2.0.0
  *
- * \param ctx       The context to set up.
+ * \param ctx       The context to set up. This must not be \c NULL.
  * \param md_info   The information structure of the message-digest algorithm
  *                  to use.
  *
@@ -188,9 +188,9 @@
  *                  mbedtls_md_free(). Makes it necessary to call
  *                  mbedtls_md_free() later.
  *
- * \param ctx       The context to set up.
+ * \param ctx       The context to set up. This must not be \c NULL.
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  * \param hmac      Defines if HMAC is used. 0: HMAC is not used (saves some memory),
  *                  or non-zero: HMAC is used with this context.
  *
@@ -214,8 +214,8 @@
  * \warning         This function clones the message-digest state, not the
  *                  HMAC state.
  *
- * \param dst       The destination context.
- * \param src       The context to be cloned.
+ * \param dst       The destination context. This must not be \c NULL.
+ * \param src       The context to be cloned. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.
@@ -228,7 +228,7 @@
  *                  message-digest information structure.
  *
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  *
  * \return          The size of the message-digest output in Bytes.
  */
@@ -239,7 +239,7 @@
  *                  message-digest information structure.
  *
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  *
  * \return          The type of the message digest.
  */
@@ -250,7 +250,7 @@
  *                  message-digest information structure.
  *
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  *
  * \return          The name of the message digest.
  */
@@ -280,7 +280,7 @@
  *                  Afterwards, call mbedtls_md_finish().
  *
  * \param ctx       The generic message-digest context.
- * \param input     The buffer holding the input data.
+ * \param input     The buffer holding the input data. This must not be \c NULL.
  * \param ilen      The length of the input data.
  *
  * \return          \c 0 on success.
@@ -302,6 +302,7 @@
  *
  * \param ctx       The generic message-digest context.
  * \param output    The buffer for the generic message-digest checksum result.
+ *                  This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -318,10 +319,11 @@
  *                 Output = message_digest(input buffer).
  *
  * \param md_info  The information structure of the message-digest algorithm
- *                 to use.
+ *                 to use. This must not be \c NULL.
  * \param input    The buffer holding the data.
  * \param ilen     The length of the input data.
  * \param output   The generic message-digest checksum result.
+ *                 This must not be \c NULL.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -339,9 +341,10 @@
  *                 Output = message_digest(file contents).
  *
  * \param md_info  The information structure of the message-digest algorithm
- *                 to use.
- * \param path     The input file name.
+ *                 to use. This must not be \c NULL.
+ * \param path     The input file name. This must not be \c NULL.
  * \param output   The generic message-digest checksum result.
+ *                 This must not be \c NULL.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_MD_FILE_IO_ERROR on an I/O error accessing
@@ -363,7 +366,7 @@
  *
  * \param ctx       The message digest context containing an embedded HMAC
  *                  context.
- * \param key       The HMAC secret key.
+ * \param key       The HMAC secret key. This must not be \c NULL.
  * \param keylen    The length of the HMAC key in Bytes.
  *
  * \return          \c 0 on success.
@@ -407,7 +410,7 @@
  *
  * \param ctx       The message digest context containing an embedded HMAC
  *                  context.
- * \param output    The generic HMAC checksum result.
+ * \param output    The generic HMAC checksum result. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -424,7 +427,7 @@
  *                  input.
  *
  * \param ctx       The message digest context containing an embedded HMAC
- *                  context.
+ *                  context. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -443,12 +446,12 @@
  *                 output = generic HMAC(hmac key, input buffer).
  *
  * \param md_info  The information structure of the message-digest algorithm
- *                 to use.
- * \param key      The HMAC secret key.
+ *                 to use. This must not be \c NULL.
+ * \param key      The HMAC secret key. This must not be \c NULL.
  * \param keylen   The length of the HMAC secret key in Bytes.
  * \param input    The buffer holding the input data.
  * \param ilen     The length of the input data.
- * \param output   The generic HMAC result.
+ * \param output   The generic HMAC result. This must not be \c NULL.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification