diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index 121575a51..dcbc04792 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -1,10 +1,15 @@
 /**
  * \file ctr_drbg.h
  *
- * \brief    CTR_DRBG is based on AES-256, as defined in <em>NIST SP 800-90A:
- *           Recommendation for Random Number Generation Using Deterministic
- *           Random Bit Generators</em>.
+ * \brief    This file contains CTR_DRBG definitions and functions.
  *
+ * CTR_DRBG is a standardized way of building a PRNG from a block-cipher
+ * in counter mode operation, as defined in <em>NIST SP 800-90A:
+ * Recommendation for Random Number Generation Using Deterministic Random
+ * Bit Generators</em>.
+ *
+ * The Mbed TLS implementation of CTR_DRBG uses AES-256 as the underlying
+ * block cipher.
  */
 /*
  *  Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
@@ -156,8 +161,8 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
                         identifiers. Can be NULL.
  * \param len           The length of the personalization data.
  *
- * \return              \c 0 on success, or
- *                      #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
  */
 int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
                    int (*f_entropy)(void *, unsigned char *, size_t),
@@ -216,22 +221,24 @@ void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx,
  * \param additional    Additional data to add to the state. Can be NULL.
  * \param len           The length of the additional data.
  *
- * \return   \c 0 on success, or
- *           #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
  */
 int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
                      const unsigned char *additional, size_t len );
 
 /**
- * \brief               This function updates the state of the CTR_DRBG context.
+ * \brief              This function updates the state of the CTR_DRBG context.
  *
- * \param ctx           The CTR_DRBG context.
- * \param additional    The data to update the state with.
- * \param add_len       Length of \p additional data.
+ * \note               If \p add_len is greater than
+ *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first
+ *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
+ *                     The remaining Bytes are silently discarded.
+ *
+ * \param ctx          The CTR_DRBG context.
+ * \param additional   The data to update the state with.
+ * \param add_len      Length of \p additional data.
  *
- * \note     If \p add_len is greater than #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT,
- *           only the first #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
- *           The remaining Bytes are silently discarded.
  */
 void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
                       const unsigned char *additional, size_t add_len );
@@ -249,8 +256,8 @@ void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
  * \param additional    Additional data to update. Can be NULL.
  * \param add_len       The length of the additional data.
  *
- * \return    \c 0 on success, or
- *            #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
+ * \return    \c 0 on success.
+ * \return    #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
  *            #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
  */
 int mbedtls_ctr_drbg_random_with_add( void *p_rng,
@@ -267,8 +274,8 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng,
  * \param output        The buffer to fill.
  * \param output_len    The length of the buffer.
  *
- * \return              \c 0 on success, or
- *                      #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
  *                      #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
  */
 int mbedtls_ctr_drbg_random( void *p_rng,
@@ -281,9 +288,9 @@ int mbedtls_ctr_drbg_random( void *p_rng,
  * \param ctx           The CTR_DRBG context.
  * \param path          The name of the file.
  *
- * \return              \c 0 on success,
- *                      #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, or
- *                      #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
  *                      failure.
  */
 int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
@@ -295,9 +302,9 @@ int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char
  * \param ctx           The CTR_DRBG context.
  * \param path          The name of the file.
  *
- * \return              \c 0 on success,
- *                      #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error,
- *                      #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
  *                      #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure.
  */
 int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
@@ -306,7 +313,8 @@ int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char
 /**
  * \brief               The CTR_DRBG checkup routine.
  *
- * \return              \c 0 on success, or \c 1 on failure.
+ * \return              \c 0 on success.
+ * \return              \c 1 on failure.
  */
 int mbedtls_ctr_drbg_self_test( int verbose );