diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index b2c57a4..3f3a25d 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -84,7 +84,7 @@
  *                  to make references valid, and prepare the context
  *                  for mbedtls_ccm_setkey() or mbedtls_ccm_free().
  *
- * \param ctx       The CCM context to initialize. Must not be \c NULL.
+ * \param ctx       The CCM context to initialize. This must not be \c NULL.
  */
 void mbedtls_ccm_init( mbedtls_ccm_context *ctx );
 
@@ -92,10 +92,10 @@
  * \brief           This function initializes the CCM context set in the
  *                  \p ctx parameter and sets the encryption key.
  *
- * \param ctx       The CCM context to initialize. Must be an initialized
+ * \param ctx       The CCM context to initialize. This must be an initialized
  *                  context.
  * \param cipher    The 128-bit block cipher to use.
- * \param key       The encryption key. Must not be \c NULL.
+ * \param key       The encryption key. This must not be \c NULL.
  * \param keybits   The key size in bits. This must be acceptable by the cipher.
  *
  * \return          \c 0 on success.
@@ -110,7 +110,8 @@
  * \brief   This function releases and clears the specified CCM context
  *          and underlying cipher sub-context.
  *
- * \param ctx       The CCM context to clear. Must be an initialized context.
+ * \param ctx       The CCM context to clear. This must be an initialized
+ *                  context.
  *
  * \note            If ctx is \c NULL, the function has no effect.
  */
@@ -125,26 +126,26 @@
  *                  \p tag = \p output + \p length, and make sure that the
  *                  output buffer is at least \p length + \p tag_len wide.
  *
- * \param ctx       The CCM context to use for encryption. Must be an
+ * \param ctx       The CCM context to use for encryption. This must be an
  *                  initialized context.
  * \param length    The length of the input data in Bytes.
- * \param iv        Initialization vector (nonce). Must be a readable buffer of
- *                  at least \p iv_len Bytes.
+ * \param iv        Initialization vector (nonce). This must be a readable
+ *                  buffer of at least \p iv_len Bytes.
  * \param iv_len    The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
  *                  or 13. The length L of the message length field is
  *                  15 - \p iv_len.
  * \param add       The additional data field. If \p add_len is greater than
  *                  zero, \p add must be a readable buffer of at least that
- *                  length.
+ *                  length. If `pad_len == 0`, this may be \c NULL.
  * \param add_len   The length of additional data in Bytes.
- *                  Must be less than 2^16 - 2^8.
+ *                  This must be less than 2^16 - 2^8.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, \p input must be a readable buffer of at least
  *                  that length.
  * \param output    The buffer holding the output data. If \p length is greater
  *                  than zero, \p output must be a writable buffer of at least
  *                  that length.
- * \param tag       The buffer holding the authentication field. Must be a
+ * \param tag       The buffer holding the authentication field. This must be a
  *                  readable buffer of at least \p tag_len Bytes.
  * \param tag_len   The length of the authentication field to generate in Bytes:
  *                  4, 6, 8, 10, 12, 14 or 16.
@@ -171,31 +172,31 @@
  *                  the tag length has to be encoded into the \p iv passed to
  *                  this function.
  *
- * \param ctx       The CCM context to use for encryption. Must be an
+ * \param ctx       The CCM context to use for encryption. This must be an
  *                  initialized context.
  * \param length    The length of the input data in Bytes.
- * \param iv        Initialization vector (nonce). Must be a readable buffer of
- *                  at least \p iv_len Bytes.
+ * \param iv        Initialization vector (nonce). This must be a readable
+ *                  buffer of at least \p iv_len Bytes.
  * \param iv_len    The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
  *                  or 13. The length L of the message length field is
  *                  15 - \p iv_len.
  * \param add       The additional data field. If \p add_len is greater than
  *                  zero, \p add must be a readable buffer of at least that
- *                  length.
+ *                  length. If `pad_len == 0`, this may be \c NULL.
  * \param add_len   The length of additional data in Bytes.
- *                  Must be less than 2^16 - 2^8.
+ *                  This must be less than 2^16 - 2^8.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, \p input must be a readable buffer of at least
  *                  that length.
  * \param output    The buffer holding the output data. If \p length is greater
  *                  than zero, \p output must be a writable buffer of at least
  *                  that length.
- * \param tag       The buffer holding the authentication field. Must be a
+ * \param tag       The buffer holding the authentication field. This must be a
  *                  readable buffer of at least \p tag_len Bytes.
  * \param tag_len   The length of the authentication field to generate in Bytes:
  *                  0, 4, 6, 8, 10, 12, 14 or 16.
  *
- * \warning         Passing 0 as \p tag_len means that the message is no
+ * \warning         Passing \c 0 as \p tag_len means that the message is no
  *                  longer authenticated.
  *
  * \return          \c 0 on success.
@@ -211,26 +212,26 @@
  * \brief           This function performs a CCM authenticated decryption of a
  *                  buffer.
  *
- * \param ctx       The CCM context to use for decryption. Must be an
+ * \param ctx       The CCM context to use for decryption. This must be an
  *                  initialized context.
  * \param length    The length of the input data in Bytes.
- * \param iv        Initialization vector (nonce). Must be a readable buffer of
- *                  at least \p iv_len Bytes.
+ * \param iv        Initialization vector (nonce). This must be a readable
+ *                  buffer of at least \p iv_len Bytes.
  * \param iv_len    The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
  *                  or 13. The length L of the message length field is
  *                  15 - \p iv_len.
  * \param add       The additional data field. If \p add_len is greater than
  *                  zero, \p add must be a readable buffer of at least that
- *                  length.
+ *                  length. If `pad_len == 0`, this may be \c NULL.
  * \param add_len   The length of additional data in Bytes.
- *                  Must be less than 2^16 - 2^8.
+ *                  This must be less than 2^16 - 2^8.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, \p input must be a readable buffer of at least
  *                  that length.
  * \param output    The buffer holding the output data. If \p length is greater
  *                  than zero, \p output must be a writable buffer of at least
  *                  that length.
- * \param tag       The buffer holding the authentication field. Must be a
+ * \param tag       The buffer holding the authentication field. This must be a
  *                  readable buffer of at least \p tag_len Bytes.
  * \param tag_len   The length of the authentication field to generate in Bytes:
  *                  4, 6, 8, 10, 12, 14 or 16.
@@ -254,31 +255,31 @@
  *                  this function as \p tag_len. (\p tag needs to be adjusted
  *                  accordingly.)
  *
- * \param ctx       The CCM context to use for decryption. Must be an
+ * \param ctx       The CCM context to use for decryption. This must be an
  *                  initialized context.
  * \param length    The length of the input data in Bytes.
- * \param iv        Initialization vector (nonce). Must be a readable buffer of
- *                  at least \p iv_len Bytes.
+ * \param iv        Initialization vector (nonce). This must be a readable
+ *                  buffer of at least \p iv_len Bytes.
  * \param iv_len    The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
  *                  or 13. The length L of the message length field is
  *                  15 - \p iv_len.
  * \param add       The additional data field. If \p add_len is greater than
  *                  zero, \p add must be a readable buffer of at least that
- *                  length.
+ *                  length. If `pad_len == 0`, this may be \c NULL.
  * \param add_len   The length of additional data in Bytes.
- *                  Must be less than 2^16 - 2^8.
+ *                  This must be less than 2^16 - 2^8.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, \p input must be a readable buffer of at least
  *                  that length.
  * \param output    The buffer holding the output data. If \p length is greater
  *                  than zero, \p output must be a writable buffer of at least
  *                  that length.
- * \param tag       The buffer holding the authentication field. Must be a
+ * \param tag       The buffer holding the authentication field. This must be a
  *                  readable buffer of at least \p tag_len Bytes.
  * \param tag_len   The length of the authentication field in Bytes.
  *                  0, 4, 6, 8, 10, 12, 14 or 16.
  *
- * \warning         Passing 0 as \p tag_len means that the message is no
+ * \warning         Passing \c 0 as \p tag_len means that the message is nos
  *                  longer authenticated.
  *
  * \return          \c 0 on success.