mbedtls/include/mbedtls/ecdsa.h
Janos Follath f1713e96c9 Add a safer deterministic ECDSA function
`mbedtls_ecdsa_sign_det` reuses the internal HMAC-DRBG instance to
implement blinding. The advantage of this is that the algorithm is
deterministic too, not just the resulting signature. The drawback is
that the blinding is always the same for the same key and message.
This diminishes the efficiency of blinding and leaks information about
the private key.

A function that takes external randomness fixes this weakness.
2019-03-06 14:41:44 +00:00

605 lines
28 KiB
C

/**
* \file ecdsa.h
*
* \brief This file contains ECDSA definitions and functions.
*
* 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
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* 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)
*/
#ifndef MBEDTLS_ECDSA_H
#define MBEDTLS_ECDSA_H
#if !defined(MBEDTLS_CONFIG_FILE)
#include "config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include "ecp.h"
#include "md.h"
/*
* RFC-4492 page 20:
*
* Ecdsa-Sig-Value ::= SEQUENCE {
* r INTEGER,
* s INTEGER
* }
*
* Size is at most
* 1 (tag) + 1 (len) + 1 (initial 0) + ECP_MAX_BYTES for each of r and s,
* twice that + 1 (tag) + 2 (len) for the sequence
* (assuming ECP_MAX_BYTES is less than 126 for r and s,
* and less than 124 (total len <= 255) for the sequence)
*/
#if MBEDTLS_ECP_MAX_BYTES > 124
#error "MBEDTLS_ECP_MAX_BYTES bigger than expected, please fix MBEDTLS_ECDSA_MAX_LEN"
#endif
/** The maximal size of an ECDSA signature in Bytes. */
#define MBEDTLS_ECDSA_MAX_LEN ( 3 + 2 * ( 3 + MBEDTLS_ECP_MAX_BYTES ) )
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief The ECDSA context structure.
*
* \warning Performing multiple operations concurrently on the same
* ECDSA context is not supported; objects of this type
* should not be shared between multiple threads.
*/
typedef mbedtls_ecp_keypair mbedtls_ecdsa_context;
#if defined(MBEDTLS_ECP_RESTARTABLE)
/**
* \brief Internal restart context for ecdsa_verify()
*
* \note Opaque struct, defined in ecdsa.c
*/
typedef struct mbedtls_ecdsa_restart_ver mbedtls_ecdsa_restart_ver_ctx;
/**
* \brief Internal restart context for ecdsa_sign()
*
* \note Opaque struct, defined in ecdsa.c
*/
typedef struct mbedtls_ecdsa_restart_sig mbedtls_ecdsa_restart_sig_ctx;
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
/**
* \brief Internal restart context for ecdsa_sign_det()
*
* \note Opaque struct, defined in ecdsa.c
*/
typedef struct mbedtls_ecdsa_restart_det mbedtls_ecdsa_restart_det_ctx;
#endif
/**
* \brief General context for resuming ECDSA operations
*/
typedef struct
{
mbedtls_ecp_restart_ctx ecp; /*!< base context for ECP restart and
shared administrative info */
mbedtls_ecdsa_restart_ver_ctx *ver; /*!< ecdsa_verify() sub-context */
mbedtls_ecdsa_restart_sig_ctx *sig; /*!< ecdsa_sign() sub-context */
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
mbedtls_ecdsa_restart_det_ctx *det; /*!< ecdsa_sign_det() sub-context */
#endif
} mbedtls_ecdsa_restart_ctx;
#else /* MBEDTLS_ECP_RESTARTABLE */
/* Now we can declare functions that take a pointer to that */
typedef void mbedtls_ecdsa_restart_ctx;
#endif /* MBEDTLS_ECP_RESTARTABLE */
/**
* \brief This function computes the ECDSA signature of a
* previously-hashed message.
*
* \note The deterministic version implemented in
* mbedtls_ecdsa_sign_det() 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 defined in <em>Standards for Efficient Cryptography Group
* (SECG): SEC1 Elliptic Curve Cryptography</em>, section
* 4.1.3, step 5.
*
* \see ecp.h
*
* \param grp The context for the elliptic curve to use.
* This must be initialized and have group parameters
* set, for example through mbedtls_ecp_group_load().
* \param r The MPI context in which to store the first part
* the signature. This must be initialized.
* \param s The MPI context in which to store the second part
* the signature. This must be initialized.
* \param d The private signing key. This must be initialized.
* \param buf The content to be signed. This is usually the hash of
* the original data to be signed. This must be a readable
* buffer of length \p blen Bytes. It may be \c NULL if
* \p blen is zero.
* \param blen The length of \p buf in Bytes.
* \param f_rng The RNG function. This must not be \c NULL.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng doesn't need a context parameter.
*
* \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,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
/**
* \brief This function computes the ECDSA signature of a
* previously-hashed message, deterministic version.
*
* 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
* defined in <em>Standards for Efficient Cryptography Group
* (SECG): SEC1 Elliptic Curve Cryptography</em>, section
* 4.1.3, step 5.
*
* \warning Since the output of the internal RNG is always the same for
* the same key and message, this limits the efficiency of
* blinding and leaks information through side channels. For
* secure behavior use mbedtls_ecdsa_sign_det_ext() instead.
*
* (Optimally the blinding is a random value that is different
* on every execution. In this case the blinding is still
* random from the attackers perspective, but is the same on
* each execution. This means that this blinding does not
* prevent attackers from recovering secrets by combining
* several measurement traces, but may prevent some attacks
* that exploit relationships between secret data.)
*
* \see ecp.h
*
* \param grp The context for the elliptic curve to use.
* This must be initialized and have group parameters
* set, for example through mbedtls_ecp_group_load().
* \param r The MPI context in which to store the first part
* the signature. This must be initialized.
* \param s The MPI context in which to store the second part
* the signature. This must be initialized.
* \param d The private signing key. This must be initialized
* and setup, for example through mbedtls_ecp_gen_privkey().
* \param buf The hashed content to be signed. This must be a readable
* buffer of length \p blen Bytes. It may be \c NULL if
* \p blen is zero.
* \param blen The length of \p buf in Bytes.
* \param md_alg The hash algorithm used to hash the original data.
*
* \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,
mbedtls_md_type_t md_alg );
/**
* \brief This function computes the ECDSA signature of a
* previously-hashed message, deterministic version.
*
* 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
* defined in <em>Standards for Efficient Cryptography Group
* (SECG): SEC1 Elliptic Curve Cryptography</em>, section
* 4.1.3, step 5.
*
* \see ecp.h
*
* \param grp The context for the elliptic curve to use.
* This must be initialized and have group parameters
* set, for example through mbedtls_ecp_group_load().
* \param r The MPI context in which to store the first part
* the signature. This must be initialized.
* \param s The MPI context in which to store the second part
* the signature. This must be initialized.
* \param d The private signing key. This must be initialized
* and setup, for example through mbedtls_ecp_gen_privkey().
* \param buf The hashed content to be signed. This must be a readable
* buffer of length \p blen Bytes. It may be \c NULL if
* \p blen is zero.
* \param blen The length of \p buf in Bytes.
* \param md_alg The hash algorithm used to hash the original data.
* \param f_rng_blind The RNG function used for blinding. This must not be
* \c NULL.
* \param p_rng_blind The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng doesn't need a context parameter.
*
* \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_ext( mbedtls_ecp_group *grp, mbedtls_mpi *r,
mbedtls_mpi *s, const mbedtls_mpi *d,
const unsigned char *buf, size_t blen,
mbedtls_md_type_t md_alg,
int (*f_rng_blind)(void *, unsigned char *,
size_t),
void *p_rng_blind );
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
/**
* \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
* defined in <em>Standards for Efficient Cryptography Group
* (SECG): SEC1 Elliptic Curve Cryptography</em>, section
* 4.1.4, step 3.
*
* \see ecp.h
*
* \param grp The ECP group to use.
* This must be initialized and have group parameters
* set, for example through mbedtls_ecp_group_load().
* \param buf The hashed content that was signed. This must be a readable
* buffer of length \p blen Bytes. It may be \c NULL if
* \p blen is zero.
* \param blen The length of \p buf in Bytes.
* \param Q The public key to use for verification. This must be
* initialized and setup.
* \param r The first integer of the signature.
* This must be initialized.
* \param s The second integer of the signature.
* This must be initialized.
*
* \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 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>.
*
* \warning It is not thread-safe to use the same context in
* multiple threads.
*
* \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 If the bitlength of the message hash is larger than the
* 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.
*
* \see ecp.h
*
* \param ctx The ECDSA context to use. This must be initialized
* and have a group and private key bound to it, for example
* via mbedtls_ecdsa_genkey() or mbedtls_ecdsa_from_keypair().
* \param md_alg The message digest that was used to hash the message.
* \param hash The message hash to be signed. This must be a readable
* buffer of length \p blen Bytes.
* \param hlen The length of the hash \p hash in Bytes.
* \param sig The buffer to which to write the signature. This must be a
* writable buffer of length 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.
* \param slen The address at which to store the actual length of
* the signature written. Must not be \c NULL.
* \param f_rng The RNG function. This must not be \c NULL if
* #MBEDTLS_ECDSA_DETERMINISTIC is unset. Otherwise,
* it is unused and may be set to \c NULL.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng is \c NULL or doesn't use a 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,
unsigned char *sig, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
/**
* \brief This function computes the ECDSA signature and writes it
* to a buffer, in a restartable way.
*
* \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 The ECDSA context to use. This must be initialized
* and have a group and private key bound to it, for example
* via mbedtls_ecdsa_genkey() or mbedtls_ecdsa_from_keypair().
* \param md_alg The message digest that was used to hash the message.
* \param hash The message hash to be signed. This must be a readable
* buffer of length \p blen Bytes.
* \param hlen The length of the hash \p hash in Bytes.
* \param sig The buffer to which to write the signature. This must be a
* writable buffer of length 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.
* \param slen The address at which to store the actual length of
* the signature written. Must not be \c NULL.
* \param f_rng The RNG function. This must not be \c NULL if
* #MBEDTLS_ECDSA_DETERMINISTIC is unset. Otherwise,
* it is unused and may be set to \c NULL.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng is \c NULL or doesn't use a context.
* \param rs_ctx The restart context to use. This may be \c NULL to disable
* restarting. If it is not \c NULL, it must point to an
* initialized restart context.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
* operations was reached: see \c mbedtls_ecp_set_max_ops().
* \return Another \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_restartable( mbedtls_ecdsa_context *ctx,
mbedtls_md_type_t md_alg,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
mbedtls_ecdsa_restart_ctx *rs_ctx );
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
#if ! defined(MBEDTLS_DEPRECATED_REMOVED)
#if defined(MBEDTLS_DEPRECATED_WARNING)
#define MBEDTLS_DEPRECATED __attribute__((deprecated))
#else
#define MBEDTLS_DEPRECATED
#endif
/**
* \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>.
*
* 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>.
*
* \warning It is not thread-safe to use the same context in
* multiple threads.
*
* \note If the bitlength of the message hash is larger than the
* 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.
*
* \see ecp.h
*
* \deprecated Superseded by mbedtls_ecdsa_write_signature() in
* Mbed TLS version 2.0 and later.
*
* \param ctx The ECDSA context to use. This must be initialized
* and have a group and private key bound to it, for example
* via mbedtls_ecdsa_genkey() or mbedtls_ecdsa_from_keypair().
* \param hash The message hash to be signed. This must be a readable
* buffer of length \p blen Bytes.
* \param hlen The length of the hash \p hash in Bytes.
* \param sig The buffer to which to write the signature. This must be a
* writable buffer of length 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.
* \param slen The address at which to store the actual length of
* the signature written. Must not be \c NULL.
* \param md_alg The message digest that was 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,
unsigned char *sig, size_t *slen,
mbedtls_md_type_t md_alg ) MBEDTLS_DEPRECATED;
#undef MBEDTLS_DEPRECATED
#endif /* MBEDTLS_DEPRECATED_REMOVED */
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
/**
* \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
* defined in <em>Standards for Efficient Cryptography Group
* (SECG): SEC1 Elliptic Curve Cryptography</em>, section
* 4.1.4, step 3.
*
* \see ecp.h
*
* \param ctx The ECDSA context to use. This must be initialized
* and have a group and public key bound to it.
* \param hash The message hash that was signed. This must be a readable
* buffer of length \p size Bytes.
* \param hlen The size of the hash \p hash.
* \param sig The signature to read and verify. This must be a readable
* buffer of length \p slen Bytes.
* \param slen The size of \p sig in Bytes.
*
* \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 This function reads and verifies an ECDSA signature,
* in a restartable way.
*
* \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 The ECDSA context to use. This must be initialized
* and have a group and public key bound to it.
* \param hash The message hash that was signed. This must be a readable
* buffer of length \p size Bytes.
* \param hlen The size of the hash \p hash.
* \param sig The signature to read and verify. This must be a readable
* buffer of length \p slen Bytes.
* \param slen The size of \p sig in Bytes.
* \param rs_ctx The restart context to use. This may be \c NULL to disable
* restarting. If it is not \c NULL, it must point to an
* initialized restart context.
*
* \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 #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
* operations was reached: see \c mbedtls_ecp_set_max_ops().
* \return Another \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_ERR_MPI_XXX
* error code on failure for any other reason.
*/
int mbedtls_ecdsa_read_signature_restartable( mbedtls_ecdsa_context *ctx,
const unsigned char *hash, size_t hlen,
const unsigned char *sig, size_t slen,
mbedtls_ecdsa_restart_ctx *rs_ctx );
/**
* \brief This function generates an ECDSA keypair on the given curve.
*
* \see ecp.h
*
* \param ctx The ECDSA context to store the keypair in.
* This must be initialized.
* \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 to use. This must not be \c NULL.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng doesn't need a context argument.
*
* \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 This function sets up an ECDSA context from an EC key pair.
*
* \see ecp.h
*
* \param ctx The ECDSA context to setup. This must be initialized.
* \param key The EC key to use. This must be initialized and hold
* a private-public key pair or a public key. In the former
* case, the ECDSA context may be used for signature creation
* and verification after this call. In the latter case, it
* may be used for signature verification.
*
* \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 This function initializes an ECDSA context.
*
* \param ctx The ECDSA context to initialize.
* This must not be \c NULL.
*/
void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx );
/**
* \brief This function frees an ECDSA context.
*
* \param ctx The ECDSA context to free. This may be \c NULL,
* in which case this function does nothing. If it
* is not \c NULL, it must be initialized.
*/
void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx );
#if defined(MBEDTLS_ECP_RESTARTABLE)
/**
* \brief Initialize a restart context.
*
* \param ctx The restart context to initialize.
* This must not be \c NULL.
*/
void mbedtls_ecdsa_restart_init( mbedtls_ecdsa_restart_ctx *ctx );
/**
* \brief Free the components of a restart context.
*
* \param ctx The restart context to free. This may be \c NULL,
* in which case this function does nothing. If it
* is not \c NULL, it must be initialized.
*/
void mbedtls_ecdsa_restart_free( mbedtls_ecdsa_restart_ctx *ctx );
#endif /* MBEDTLS_ECP_RESTARTABLE */
#ifdef __cplusplus
}
#endif
#endif /* ecdsa.h */