diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index 01cd826..121575a 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -1,10 +1,13 @@
 /**
  * \file ctr_drbg.h
  *
- * \brief CTR_DRBG based on AES-256 (NIST SP 800-90)
+ * \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>.
+ *
  */
 /*
- *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -19,8 +22,9 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  *
- *  This file is part of mbed TLS (https://tls.mbed.org)
+ *  This file is part of Mbed TLS (https://tls.mbed.org)
  */
+
 #ifndef MBEDTLS_CTR_DRBG_H
 #define MBEDTLS_CTR_DRBG_H
 
@@ -31,78 +35,95 @@
 #endif
 
 #define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED        -0x0034  /**< The entropy source failed. */
-#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG              -0x0036  /**< Too many random requested in single call. */
-#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG                -0x0038  /**< Input too large (Entropy + additional). */
-#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR                -0x003A  /**< Read/write error in file. */
+#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG              -0x0036  /**< The requested random buffer length is too big. */
+#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG                -0x0038  /**< The input (entropy + additional data) is too large. */
+#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR                -0x003A  /**< Read or write error in file. */
 
-#define MBEDTLS_CTR_DRBG_BLOCKSIZE          16      /**< Block size used by the cipher                  */
-#define MBEDTLS_CTR_DRBG_KEYSIZE            32      /**< Key size used by the cipher                    */
-#define MBEDTLS_CTR_DRBG_KEYBITS            ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 )
-#define MBEDTLS_CTR_DRBG_SEEDLEN            ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE )
-                                            /**< The seed length (counter + AES key)            */
+#define MBEDTLS_CTR_DRBG_BLOCKSIZE          16 /**< The block size used by the cipher. */
+#define MBEDTLS_CTR_DRBG_KEYSIZE            32 /**< The key size used by the cipher. */
+#define MBEDTLS_CTR_DRBG_KEYBITS            ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 ) /**< The key size for the DRBG operation, in bits. */
+#define MBEDTLS_CTR_DRBG_SEEDLEN            ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE ) /**< The seed length, calculated as (counter + AES key). */
 
 /**
  * \name SECTION: Module settings
  *
  * The configuration options you can set for this module are in this section.
- * Either change them in config.h or define them on the compiler command line.
+ * Either change them in config.h or define them using the compiler command
+ * line.
  * \{
  */
 
 #if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN)
 #if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
-#define MBEDTLS_CTR_DRBG_ENTROPY_LEN        48      /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
+#define MBEDTLS_CTR_DRBG_ENTROPY_LEN        48
+/**< The amount of entropy used per seed by default:
+ * <ul><li>48 with SHA-512.</li>
+ * <li>32 with SHA-256.</li></ul>
+ */
 #else
-#define MBEDTLS_CTR_DRBG_ENTROPY_LEN        32      /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
+#define MBEDTLS_CTR_DRBG_ENTROPY_LEN        32
+/**< Amount of entropy used per seed by default:
+ * <ul><li>48 with SHA-512.</li>
+ * <li>32 with SHA-256.</li></ul>
+ */
 #endif
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
-#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL    10000   /**< Interval before reseed is performed by default */
+#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL    10000
+/**< The interval before reseed is performed by default. */
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_INPUT)
-#define MBEDTLS_CTR_DRBG_MAX_INPUT          256     /**< Maximum number of additional input bytes */
+#define MBEDTLS_CTR_DRBG_MAX_INPUT          256
+/**< The maximum number of additional input Bytes. */
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_REQUEST)
-#define MBEDTLS_CTR_DRBG_MAX_REQUEST        1024    /**< Maximum number of requested bytes per call */
+#define MBEDTLS_CTR_DRBG_MAX_REQUEST        1024
+/**< The maximum number of requested Bytes per call. */
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT)
-#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT     384     /**< Maximum size of (re)seed buffer */
+#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT     384
+/**< The maximum size of seed or reseed buffer. */
 #endif
 
 /* \} name SECTION: Module settings */
 
-#define MBEDTLS_CTR_DRBG_PR_OFF             0       /**< No prediction resistance       */
-#define MBEDTLS_CTR_DRBG_PR_ON              1       /**< Prediction resistance enabled  */
+#define MBEDTLS_CTR_DRBG_PR_OFF             0
+/**< Prediction resistance is disabled. */
+#define MBEDTLS_CTR_DRBG_PR_ON              1
+/**< Prediction resistance is enabled. */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
- * \brief          CTR_DRBG context structure
+ * \brief          The CTR_DRBG context structure.
  */
 typedef struct
 {
-    unsigned char counter[16];  /*!<  counter (V)       */
-    int reseed_counter;         /*!<  reseed counter    */
-    int prediction_resistance;  /*!<  enable prediction resistance (Automatic
-                                      reseed before every random generation)  */
-    size_t entropy_len;         /*!<  amount of entropy grabbed on each
-                                      (re)seed          */
-    int reseed_interval;        /*!<  reseed interval   */
+    unsigned char counter[16];  /*!< The counter (V). */
+    int reseed_counter;         /*!< The reseed counter. */
+    int prediction_resistance;  /*!< This determines whether prediction
+                                     resistance is enabled, that is
+                                     whether to systematically reseed before
+                                     each random generation. */
+    size_t entropy_len;         /*!< The amount of entropy grabbed on each
+                                     seed or reseed operation. */
+    int reseed_interval;        /*!< The reseed interval. */
 
-    mbedtls_aes_context aes_ctx;        /*!<  AES context       */
+    mbedtls_aes_context aes_ctx;        /*!< The AES context. */
 
     /*
      * Callbacks (Entropy)
      */
     int (*f_entropy)(void *, unsigned char *, size_t);
+                                /*!< The entropy callback function. */
 
-    void *p_entropy;            /*!<  context for the entropy function */
+    void *p_entropy;            /*!< The context for the entropy function. */
 
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_threading_mutex_t mutex;
@@ -111,31 +132,32 @@
 mbedtls_ctr_drbg_context;
 
 /**
- * \brief               CTR_DRBG context initialization
- *                      Makes the context ready for mbedtls_ctr_drbg_seed() or
- *                      mbedtls_ctr_drbg_free().
+ * \brief               This function initializes the CTR_DRBG context,
+ *                      and prepares it for mbedtls_ctr_drbg_seed()
+ *                      or mbedtls_ctr_drbg_free().
  *
- * \param ctx           CTR_DRBG context to be initialized
+ * \param ctx           The CTR_DRBG context to initialize.
  */
 void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
 
 /**
- * \brief               CTR_DRBG initial seeding
- *                      Seed and setup entropy source for future reseeds.
+ * \brief               This function seeds and sets up the CTR_DRBG
+ *                      entropy source for future reseeds.
  *
- * Note: Personalization data can be provided in addition to the more generic
- *       entropy source to make this instantiation as unique as possible.
+ * \note Personalization data can be provided in addition to the more generic
+ *       entropy source, to make this instantiation as unique as possible.
  *
- * \param ctx           CTR_DRBG context to be seeded
- * \param f_entropy     Entropy callback (p_entropy, buffer to fill, buffer
- *                      length)
- * \param p_entropy     Entropy context
- * \param custom        Personalization data (Device specific identifiers)
- *                      (Can be NULL)
- * \param len           Length of personalization data
+ * \param ctx           The CTR_DRBG context to seed.
+ * \param f_entropy     The entropy callback, taking as arguments the
+ *                      \p p_entropy context, the buffer to fill, and the
+                        length of the buffer.
+ * \param p_entropy     The entropy context.
+ * \param custom        Personalization data, that is device-specific
+                        identifiers. Can be NULL.
+ * \param len           The length of the personalization data.
  *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
+ * \return              \c 0 on success, or
+ *                      #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),
@@ -144,138 +166,147 @@
                    size_t len );
 
 /**
- * \brief               Clear CTR_CRBG context data
+ * \brief               This function clears CTR_CRBG context data.
  *
- * \param ctx           CTR_DRBG context to clear
+ * \param ctx           The CTR_DRBG context to clear.
  */
 void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx );
 
 /**
- * \brief               Enable / disable prediction resistance (Default: Off)
+ * \brief               This function turns prediction resistance on or off.
+ *                      The default value is off.
  *
- * Note: If enabled, entropy is used for ctx->entropy_len before each call!
- *       Only use this if you have ample supply of good entropy!
+ * \note                If enabled, entropy is gathered at the beginning of
+ *                      every call to mbedtls_ctr_drbg_random_with_add().
+ *                      Only use this if your entropy source has sufficient
+ *                      throughput.
  *
- * \param ctx           CTR_DRBG context
- * \param resistance    MBEDTLS_CTR_DRBG_PR_ON or MBEDTLS_CTR_DRBG_PR_OFF
+ * \param ctx           The CTR_DRBG context.
+ * \param resistance    #MBEDTLS_CTR_DRBG_PR_ON or #MBEDTLS_CTR_DRBG_PR_OFF.
  */
 void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
                                          int resistance );
 
 /**
- * \brief               Set the amount of entropy grabbed on each (re)seed
- *                      (Default: MBEDTLS_CTR_DRBG_ENTROPY_LEN)
+ * \brief               This function sets the amount of entropy grabbed on each
+ *                      seed or reseed. The default value is
+ *                      #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
  *
- * \param ctx           CTR_DRBG context
- * \param len           Amount of entropy to grab
+ * \param ctx           The CTR_DRBG context.
+ * \param len           The amount of entropy to grab.
  */
 void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx,
                                size_t len );
 
 /**
- * \brief               Set the reseed interval
- *                      (Default: MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
+ * \brief               This function sets the reseed interval.
+ *                      The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
  *
- * \param ctx           CTR_DRBG context
- * \param interval      Reseed interval
+ * \param ctx           The CTR_DRBG context.
+ * \param interval      The reseed interval.
  */
 void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx,
                                    int interval );
 
 /**
- * \brief               CTR_DRBG reseeding (extracts data from entropy source)
+ * \brief               This function reseeds the CTR_DRBG context, that is
+ *                      extracts data from the entropy source.
  *
- * \param ctx           CTR_DRBG context
- * \param additional    Additional data to add to state (Can be NULL)
- * \param len           Length of additional data
+ * \param ctx           The CTR_DRBG context.
+ * \param additional    Additional data to add to the state. Can be NULL.
+ * \param len           The length of the additional data.
  *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
+ * \return   \c 0 on success, or
+ *           #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               CTR_DRBG update state
+ * \brief               This function updates the state of the CTR_DRBG context.
  *
- * \param ctx           CTR_DRBG context
- * \param additional    Additional data to update state with
- * \param add_len       Length of additional data
+ * \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 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 ones are silently discarded.
+ * \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 );
 
 /**
- * \brief               CTR_DRBG generate random with additional update input
+ * \brief   This function updates a CTR_DRBG instance with additional
+ *          data and uses it to generate random data.
  *
- * Note: Automatically reseeds if reseed_counter is reached.
+ * \note    The function automatically reseeds if the reseed counter is exceeded.
  *
- * \param p_rng         CTR_DRBG context
- * \param output        Buffer to fill
- * \param output_len    Length of the buffer
- * \param additional    Additional data to update with (Can be NULL)
- * \param add_len       Length of additional data
+ * \param p_rng         The CTR_DRBG context. This must be a pointer to a
+ *                      #mbedtls_ctr_drbg_context structure.
+ * \param output        The buffer to fill.
+ * \param output_len    The length of the buffer.
+ * \param additional    Additional data to update. Can be NULL.
+ * \param add_len       The length of the additional data.
  *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED, or
- *                      MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG
+ * \return    \c 0 on success, or
+ *            #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,
                               unsigned char *output, size_t output_len,
                               const unsigned char *additional, size_t add_len );
 
 /**
- * \brief               CTR_DRBG generate random
+ * \brief   This function uses CTR_DRBG to generate random data.
  *
- * Note: Automatically reseeds if reseed_counter is reached.
+ * \note    The function automatically reseeds if the reseed counter is exceeded.
  *
- * \param p_rng         CTR_DRBG context
- * \param output        Buffer to fill
- * \param output_len    Length of the buffer
+ * \param p_rng         The CTR_DRBG context. This must be a pointer to a
+ *                      #mbedtls_ctr_drbg_context structure.
+ * \param output        The buffer to fill.
+ * \param output_len    The length of the buffer.
  *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED, or
- *                      MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG
+ * \return              \c 0 on success, or
+ *                      #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,
                      unsigned char *output, size_t output_len );
 
 #if defined(MBEDTLS_FS_IO)
 /**
- * \brief               Write a seed file
+ * \brief               This function writes a seed file.
  *
- * \param ctx           CTR_DRBG context
- * \param path          Name of the file
+ * \param ctx           The CTR_DRBG context.
+ * \param path          The name of the file.
  *
- * \return              0 if successful,
- *                      MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, or
- *                      MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
+ * \return              \c 0 on success,
+ *                      #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, or
+ *                      #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
+ *                      failure.
  */
 int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
 
 /**
- * \brief               Read and update a seed file. Seed is added to this
- *                      instance
+ * \brief               This function reads and updates a seed file. The seed
+ *                      is added to this instance.
  *
- * \param ctx           CTR_DRBG context
- * \param path          Name of the file
+ * \param ctx           The CTR_DRBG context.
+ * \param path          The name of the file.
  *
- * \return              0 if successful,
- *                      MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error,
- *                      MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
- *                      MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG
+ * \return              \c 0 on success,
+ *                      #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error,
+ *                      #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 );
 #endif /* MBEDTLS_FS_IO */
 
 /**
- * \brief               Checkup routine
+ * \brief               The CTR_DRBG checkup routine.
  *
- * \return              0 if successful, or 1 if the test failed
+ * \return              \c 0 on success, or \c 1 on failure.
  */
 int mbedtls_ctr_drbg_self_test( int verbose );