Merge branch 'development' into iotssl-1260-non-blocking-ecc-restricted

Summary of merge conflicts:

include/mbedtls/ecdh.h -> documentation style
include/mbedtls/ecdsa.h -> documentation style
include/mbedtls/ecp.h -> alt style, new error codes, documentation style
include/mbedtls/error.h -> new error codes
library/error.c -> new error codes (generated anyway)
library/ecp.c:
    - code of an extracted function was changed
library/ssl_cli.c:
    - code addition on one side near code change on the other side
      (ciphersuite validation)
library/x509_crt.c -> various things
    - top fo file: helper structure added near old zeroize removed
    - documentation of find_parent_in()'s signature: improved on one side,
      added arguments on the other side
    - documentation of find_parent()'s signature: same as above
    - verify_chain(): variables initialised later to give compiler an
      opportunity to warn us if not initialised on a code path
    - find_parent(): funcion structure completely changed, for some reason git
      tried to insert a paragraph of the old structure...
    - merge_flags_with_cb(): data structure changed, one line was fixed with a
      cast to keep MSVC happy, this cast is already in the new version
    - in verify_restratable(): adjacent independent changes (function
      signature on one line, variable type on the next)
programs/ssl/ssl_client2.c:
    - testing for IN_PROGRESS return code near idle() (event-driven):
      don't wait for data in the the socket if ECP_IN_PROGRESS
tests/data_files/Makefile: adjacent independent additions
tests/suites/test_suite_ecdsa.data: adjacent independent additions
tests/suites/test_suite_x509parse.data: adjacent independent additions

* development: (1059 commits)
  Change symlink to hardlink to avoid permission issues
  Fix out-of-tree testing symlinks on Windows
  Updated version number to 2.10.0 for release
  Add a disabled CMAC define in the no-entropy configuration
  Adapt the ARIA test cases for new ECB function
  Fix file permissions for ssl.h
  Add ChangeLog entry for PR#1651
  Fix MicroBlaze register typo.
  Fix typo in doc and copy missing warning
  Fix edit mistake in cipher_wrap.c
  Update CTR doc for the 64-bit block cipher
  Update CTR doc for other 128-bit block ciphers
  Slightly tune ARIA CTR documentation
  Remove double declaration of mbedtls_ssl_list_ciphersuites
  Update CTR documentation
  Use zeroize function from new platform_util
  Move to new header style for ALT implementations
  Add ifdef for selftest in header file
  Fix typo in comments
  Use more appropriate type for local variable
  ...
diff --git a/include/mbedtls/ecdsa.h b/include/mbedtls/ecdsa.h
index 3440a84..710fdb9 100644
--- a/include/mbedtls/ecdsa.h
+++ b/include/mbedtls/ecdsa.h
@@ -1,9 +1,17 @@
 /**
  * \file ecdsa.h
  *
- * \brief Elliptic curve DSA
+ * \brief This file contains ECDSA definitions and functions.
  *
- *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ * The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined in
+ * <em>Standards for Efficient Cryptography Group (SECG):
+ * SEC1 Elliptic Curve Cryptography</em>.
+ * The use of ECDSA for TLS is defined in <em>RFC-4492: Elliptic Curve
+ * Cryptography (ECC) Cipher Suites for Transport Layer Security (TLS)</em>.
+ *
+ */
+/*
+ *  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
@@ -18,8 +26,9 @@
  *  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_ECDSA_H
 #define MBEDTLS_ECDSA_H
 
@@ -27,7 +36,7 @@
 #include "md.h"
 
 /*
- * RFC 4492 page 20:
+ * RFC-4492 page 20:
  *
  *     Ecdsa-Sig-Value ::= SEQUENCE {
  *         r       INTEGER,
@@ -43,7 +52,7 @@
 #if MBEDTLS_ECP_MAX_BYTES > 124
 #error "MBEDTLS_ECP_MAX_BYTES bigger than expected, please fix MBEDTLS_ECDSA_MAX_LEN"
 #endif
-/** Maximum size of an ECDSA signature in bytes */
+/** The maximal size of an ECDSA signature in Bytes. */
 #define MBEDTLS_ECDSA_MAX_LEN  ( 3 + 2 * ( 3 + MBEDTLS_ECP_MAX_BYTES ) )
 
 #ifdef __cplusplus
@@ -51,7 +60,7 @@
 #endif
 
 /**
- * \brief           ECDSA context structure
+ * \brief           The ECDSA context structure.
  *
  * \warning         Performing multiple operations concurrently on the same
  *                  ECDSA context is not supported; objects of this type
@@ -105,25 +114,31 @@
 #endif /* MBEDTLS_ECP_RESTARTABLE */
 
 /**
- * \brief           Compute ECDSA signature of a previously hashed message
+ * \brief           This function computes the ECDSA signature of a
+ *                  previously-hashed message.
  *
- * \note            The deterministic version is usually prefered.
- *
- * \param grp       ECP group
- * \param r         First output integer
- * \param s         Second output integer
- * \param d         Private signing key
- * \param buf       Message hash
- * \param blen      Length of buf
- * \param f_rng     RNG function
- * \param p_rng     RNG parameter
+ * \note            The deterministic version is usually preferred.
  *
  * \note            If the bitlength of the message hash is larger than the
- *                  bitlength of the group order, then the hash is truncated as
- *                  prescribed by SEC1 4.1.3 step 5.
+ *                  bitlength of the group order, then the hash is truncated
+ *                  as defined in <em>Standards for Efficient Cryptography Group
+ *                  (SECG): SEC1 Elliptic Curve Cryptography</em>, section
+ *                  4.1.3, step 5.
  *
- * \return          0 if successful,
- *                  or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
+ * \see             ecp.h
+ *
+ * \param grp       The ECP group.
+ * \param r         The first output integer.
+ * \param s         The second output integer.
+ * \param d         The private signing key.
+ * \param buf       The message hash.
+ * \param blen      The length of \p buf.
+ * \param f_rng     The RNG function.
+ * \param p_rng     The RNG context.
+ *
+ * \return          \c 0 on success.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX
+ *                  or \c MBEDTLS_MPI_XXX error code on failure.
  */
 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
                 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
@@ -131,23 +146,32 @@
 
 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
 /**
- * \brief           Compute ECDSA signature of a previously hashed message,
- *                  deterministic version (RFC 6979).
+ * \brief           This function computes the ECDSA signature of a
+ *                  previously-hashed message, deterministic version.
  *
- * \param grp       ECP group
- * \param r         First output integer
- * \param s         Second output integer
- * \param d         Private signing key
- * \param buf       Message hash
- * \param blen      Length of buf
- * \param md_alg    MD algorithm used to hash the message
+ *                  For more information, see <em>RFC-6979: Deterministic
+ *                  Usage of the Digital Signature Algorithm (DSA) and Elliptic
+ *                  Curve Digital Signature Algorithm (ECDSA)</em>.
  *
  * \note            If the bitlength of the message hash is larger than the
  *                  bitlength of the group order, then the hash is truncated as
- *                  prescribed by SEC1 4.1.3 step 5.
+ *                  defined in <em>Standards for Efficient Cryptography Group
+ *                  (SECG): SEC1 Elliptic Curve Cryptography</em>, section
+ *                  4.1.3, step 5.
  *
- * \return          0 if successful,
- *                  or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
+ * \see             ecp.h
+ *
+ * \param grp       The ECP group.
+ * \param r         The first output integer.
+ * \param s         The second output integer.
+ * \param d         The private signing key.
+ * \param buf       The message hash.
+ * \param blen      The length of \p buf.
+ * \param md_alg    The MD algorithm used to hash the message.
+ *
+ * \return          \c 0 on success.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_MPI_XXX
+ *                  error code on failure.
  */
 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
                     const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
@@ -155,55 +179,74 @@
 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
 
 /**
- * \brief           Verify ECDSA signature of a previously hashed message
- *
- * \param grp       ECP group
- * \param buf       Message hash
- * \param blen      Length of buf
- * \param Q         Public key to use for verification
- * \param r         First integer of the signature
- * \param s         Second integer of the signature
+ * \brief           This function verifies the ECDSA signature of a
+ *                  previously-hashed message.
  *
  * \note            If the bitlength of the message hash is larger than the
  *                  bitlength of the group order, then the hash is truncated as
- *                  prescribed by SEC1 4.1.4 step 3.
+ *                  defined in <em>Standards for Efficient Cryptography Group
+ *                  (SECG): SEC1 Elliptic Curve Cryptography</em>, section
+ *                  4.1.4, step 3.
  *
- * \return          0 if successful,
- *                  MBEDTLS_ERR_ECP_VERIFY_FAILED if signature is invalid
- *                  or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
+ * \see             ecp.h
+ *
+ * \param grp       The ECP group.
+ * \param buf       The message hash.
+ * \param blen      The length of \p buf.
+ * \param Q         The public key to use for verification.
+ * \param r         The first integer of the signature.
+ * \param s         The second integer of the signature.
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if the signature
+ *                  is invalid.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_MPI_XXX
+ *                  error code on failure for any other reason.
  */
 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
                   const unsigned char *buf, size_t blen,
                   const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s);
 
 /**
- * \brief           Compute ECDSA signature and write it to buffer,
- *                  serialized as defined in RFC 4492 page 20.
- *                  (Not thread-safe to use same context in multiple threads)
+ * \brief           This function computes the ECDSA signature and writes it
+ *                  to a buffer, serialized as defined in <em>RFC-4492:
+ *                  Elliptic Curve Cryptography (ECC) Cipher Suites for
+ *                  Transport Layer Security (TLS)</em>.
  *
- * \note            The deterministic version (RFC 6979) is used if
- *                  MBEDTLS_ECDSA_DETERMINISTIC is defined.
+ * \warning         It is not thread-safe to use the same context in
+ *                  multiple threads.
  *
- * \param ctx       ECDSA context
- * \param md_alg    Algorithm that was used to hash the message
- * \param hash      Message hash
- * \param hlen      Length of hash
- * \param sig       Buffer that will hold the signature
- * \param slen      Length of the signature written
- * \param f_rng     RNG function
- * \param p_rng     RNG parameter
+ * \note            The deterministic version is used if
+ *                  #MBEDTLS_ECDSA_DETERMINISTIC is defined. For more
+ *                  information, see <em>RFC-6979: Deterministic Usage
+ *                  of the Digital Signature Algorithm (DSA) and Elliptic
+ *                  Curve Digital Signature Algorithm (ECDSA)</em>.
  *
- * \note            The "sig" buffer must be at least as large as twice the
- *                  size of the curve used, plus 9 (eg. 73 bytes if a 256-bit
- *                  curve is used). MBEDTLS_ECDSA_MAX_LEN is always safe.
+ * \note            The \p sig buffer must be at least twice as large as the
+ *                  size of the curve used, plus 9. For example, 73 Bytes if
+ *                  a 256-bit curve is used. A buffer length of
+ *                  #MBEDTLS_ECDSA_MAX_LEN is always safe.
  *
  * \note            If the bitlength of the message hash is larger than the
  *                  bitlength of the group order, then the hash is truncated as
- *                  prescribed by SEC1 4.1.3 step 5.
+ *                  defined in <em>Standards for Efficient Cryptography Group
+ *                  (SECG): SEC1 Elliptic Curve Cryptography</em>, section
+ *                  4.1.3, step 5.
  *
- * \return          0 if successful,
- *                  or a MBEDTLS_ERR_ECP_XXX, MBEDTLS_ERR_MPI_XXX or
- *                  MBEDTLS_ERR_ASN1_XXX error code
+ * \see             ecp.h
+ *
+ * \param ctx       The ECDSA context.
+ * \param md_alg    The message digest that was used to hash the message.
+ * \param hash      The message hash.
+ * \param hlen      The length of the hash.
+ * \param sig       The buffer that holds the signature.
+ * \param slen      The length of the signature written.
+ * \param f_rng     The RNG function.
+ * \param p_rng     The RNG context.
+ *
+ * \return          \c 0 on success.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX, \c MBEDTLS_ERR_MPI_XXX or
+ *                  \c MBEDTLS_ERR_ASN1_XXX error code on failure.
  */
 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg,
                            const unsigned char *hash, size_t hlen,
@@ -212,24 +255,29 @@
                            void *p_rng );
 
 /**
- * \brief           Restartable version of \c mbedtls_ecdsa_write_signature()
+ * \brief           This function computes the ECDSA signature and writes it
+ *                  to a buffer, in a restartable way.
  *
- * \note            Performs the same job as \c mbedtls_ecdsa_write_signature()
- *                  but can return early and restart according to the limit
+ * \see             \c mbedtls_ecdsa_write_signature()
+ *
+ * \note            This function is like \c mbedtls_ecdsa_write_signature()
+ *                  but it can return early and restart according to the limit
  *                  set with \c mbedtls_ecp_set_max_ops() to reduce blocking.
  *
- * \param ctx       ECDSA context
- * \param md_alg    Algorithm that was used to hash the message
- * \param hash      Message hash
- * \param hlen      Length of hash
- * \param sig       Buffer that will hold the signature
- * \param slen      Length of the signature written
- * \param f_rng     RNG function
- * \param p_rng     RNG parameter
- * \param rs_ctx    Restart context
+ * \param ctx       The ECDSA context.
+ * \param md_alg    The message digest that was used to hash the message.
+ * \param hash      The message hash.
+ * \param hlen      The length of the hash.
+ * \param sig       The buffer that holds the signature.
+ * \param slen      The length of the signature written.
+ * \param f_rng     The RNG function.
+ * \param p_rng     The RNG context.
+ * \param rs_ctx    The restart context.
  *
- * \return          See \c mbedtls_ecdsa_write_signature(), or
- *                  MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
+ * \return          \c 0 on success.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX, \c MBEDTLS_ERR_MPI_XXX or
+ *                  \c MBEDTLS_ERR_ASN1_XXX error code on failure.
+ * \return          #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
  *                  operations was reached: see \c mbedtls_ecp_set_max_ops().
  */
 int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,
@@ -248,31 +296,44 @@
 #define MBEDTLS_DEPRECATED
 #endif
 /**
- * \brief           Compute ECDSA signature and write it to buffer,
- *                  serialized as defined in RFC 4492 page 20.
- *                  Deterministic version, RFC 6979.
- *                  (Not thread-safe to use same context in multiple threads)
+ * \brief           This function computes an ECDSA signature and writes
+ *                  it to a buffer, serialized as defined in <em>RFC-4492:
+ *                  Elliptic Curve Cryptography (ECC) Cipher Suites for
+ *                  Transport Layer Security (TLS)</em>.
  *
- * \deprecated      Superseded by mbedtls_ecdsa_write_signature() in 2.0.0
+ *                  The deterministic version is defined in <em>RFC-6979:
+ *                  Deterministic Usage of the Digital Signature Algorithm (DSA)
+ *                  and Elliptic Curve Digital Signature Algorithm (ECDSA)</em>.
  *
- * \param ctx       ECDSA context
- * \param hash      Message hash
- * \param hlen      Length of hash
- * \param sig       Buffer that will hold the signature
- * \param slen      Length of the signature written
- * \param md_alg    MD algorithm used to hash the message
+ * \warning         It is not thread-safe to use the same context in
+ *                  multiple threads.
  *
- * \note            The "sig" buffer must be at least as large as twice the
- *                  size of the curve used, plus 9 (eg. 73 bytes if a 256-bit
- *                  curve is used). MBEDTLS_ECDSA_MAX_LEN is always safe.
+ * \note            The \p sig buffer must be at least twice as large as the
+ *                  size of the curve used, plus 9. For example, 73 Bytes if a
+ *                  256-bit curve is used. A buffer length of
+ *                  #MBEDTLS_ECDSA_MAX_LEN is always safe.
  *
  * \note            If the bitlength of the message hash is larger than the
  *                  bitlength of the group order, then the hash is truncated as
- *                  prescribed by SEC1 4.1.3 step 5.
+ *                  defined in <em>Standards for Efficient Cryptography Group
+ *                  (SECG): SEC1 Elliptic Curve Cryptography</em>, section
+ *                  4.1.3, step 5.
  *
- * \return          0 if successful,
- *                  or a MBEDTLS_ERR_ECP_XXX, MBEDTLS_ERR_MPI_XXX or
- *                  MBEDTLS_ERR_ASN1_XXX error code
+ * \see             ecp.h
+ *
+ * \deprecated      Superseded by mbedtls_ecdsa_write_signature() in
+ *                  Mbed TLS version 2.0 and later.
+ *
+ * \param ctx       The ECDSA context.
+ * \param hash      The message hash.
+ * \param hlen      The length of the hash.
+ * \param sig       The buffer that holds the signature.
+ * \param slen      The length of the signature written.
+ * \param md_alg    The MD algorithm used to hash the message.
+ *
+ * \return          \c 0 on success.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX, \c MBEDTLS_ERR_MPI_XXX or
+ *                  \c MBEDTLS_ERR_ASN1_XXX error code on failure.
  */
 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
                                const unsigned char *hash, size_t hlen,
@@ -283,44 +344,57 @@
 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
 
 /**
- * \brief           Read and verify an ECDSA signature
- *
- * \param ctx       ECDSA context
- * \param hash      Message hash
- * \param hlen      Size of hash
- * \param sig       Signature to read and verify
- * \param slen      Size of sig
+ * \brief           This function reads and verifies an ECDSA signature.
  *
  * \note            If the bitlength of the message hash is larger than the
  *                  bitlength of the group order, then the hash is truncated as
- *                  prescribed by SEC1 4.1.4 step 3.
+ *                  defined in <em>Standards for Efficient Cryptography Group
+ *                  (SECG): SEC1 Elliptic Curve Cryptography</em>, section
+ *                  4.1.4, step 3.
  *
- * \return          0 if successful,
- *                  MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid,
- *                  MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if the signature is
- *                  valid but its actual length is less than siglen,
- *                  or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_ERR_MPI_XXX error code
+ * \see             ecp.h
+ *
+ * \param ctx       The ECDSA context.
+ * \param hash      The message hash.
+ * \param hlen      The size of the hash.
+ * \param sig       The signature to read and verify.
+ * \param slen      The size of \p sig.
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid.
+ * \return          #MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if there is a valid
+ *                  signature in \p sig, but its length is less than \p siglen.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_ERR_MPI_XXX
+ *                  error code on failure for any other reason.
  */
 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,
                           const unsigned char *hash, size_t hlen,
                           const unsigned char *sig, size_t slen );
 
 /**
- * \brief           Restartable version of \c mbedtls_ecdsa_read_signature()
+ * \brief           This function reads and verifies an ECDSA signature,
+ *                  in a restartable way.
  *
- * \note            Performs the same job as \c mbedtls_ecdsa_read_signature()
- *                  but can return early and restart according to the limit
+ * \see             \c mbedtls_ecdsa_read_signature()
+ *
+ * \note            This function is like \c mbedtls_ecdsa_read_signature()
+ *                  but it can return early and restart according to the limit
  *                  set with \c mbedtls_ecp_set_max_ops() to reduce blocking.
  *
- * \param ctx       ECDSA context
- * \param hash      Message hash
- * \param hlen      Size of hash
- * \param sig       Signature to read and verify
- * \param slen      Size of sig
- * \param rs_ctx    Restart context
+ * \param ctx       The ECDSA context.
+ * \param hash      The message hash.
+ * \param hlen      The size of the hash.
+ * \param sig       The signature to read and verify.
+ * \param slen      The size of \p sig.
+ * \param rs_ctx    The restart context
  *
- * \return          See \c mbedtls_ecdsa_read_signature(), or
- *                  MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid.
+ * \return          #MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if there is a valid
+ *                  signature in \p sig, but its length is less than \p siglen.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_ERR_MPI_XXX
+ *                  error code on failure for any other reason.
+ * \return          #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
  *                  operations was reached: see \c mbedtls_ecp_set_max_ops().
  */
 int mbedtls_ecdsa_read_signature_restartable( mbedtls_ecdsa_context *ctx,
@@ -329,40 +403,46 @@
                           mbedtls_ecdsa_restart_ctx *rs_ctx );
 
 /**
- * \brief           Generate an ECDSA keypair on the given curve
+ * \brief          This function generates an ECDSA keypair on the given curve.
  *
- * \param ctx       ECDSA context in which the keypair should be stored
- * \param gid       Group (elliptic curve) to use. One of the various
- *                  MBEDTLS_ECP_DP_XXX macros depending on configuration.
- * \param f_rng     RNG function
- * \param p_rng     RNG parameter
+ * \see            ecp.h
  *
- * \return          0 on success, or a MBEDTLS_ERR_ECP_XXX code.
+ * \param ctx      The ECDSA context to store the keypair in.
+ * \param gid      The elliptic curve to use. One of the various
+ *                 \c MBEDTLS_ECP_DP_XXX macros depending on configuration.
+ * \param f_rng    The RNG function.
+ * \param p_rng    The RNG context.
+ *
+ * \return         \c 0 on success.
+ * \return         An \c MBEDTLS_ERR_ECP_XXX code on failure.
  */
 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
                   int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
 
 /**
- * \brief           Set an ECDSA context from an EC key pair
+ * \brief           This function sets an ECDSA context from an EC key pair.
  *
- * \param ctx       ECDSA context to set
- * \param key       EC key to use
+ * \see             ecp.h
  *
- * \return          0 on success, or a MBEDTLS_ERR_ECP_XXX code.
+ * \param ctx       The ECDSA context to set.
+ * \param key       The EC key to use.
+ *
+ * \return          \c 0 on success.
+ * \return          An \c MBEDTLS_ERR_ECP_XXX code on failure.
  */
 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key );
 
 /**
- * \brief           Initialize context
+ * \brief           This function initializes an ECDSA context.
  *
- * \param ctx       Context to initialize
+ * \param ctx       The ECDSA context to initialize.
  */
 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx );
 
 /**
- * \brief           Free context
+ * \brief           This function frees an ECDSA context.
  *
- * \param ctx       Context to free
+ * \param ctx       The ECDSA context to free.
  */
 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx );