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0a5154b8a1
In the ecdsa.c sample application we don't use hashing, we use ecdsa directly on a buffer containing plain text. Although the text explains that it should be the message hash it still can be confusing. Any misunderstandings here are potentially very dangerous, because ECDSA truncates the message hash if necessary and this can lead to trivial signature forgeries if the API is misused and the message is passed directly to the function without hashing. This commit adds a hash computation step to the ecdsa.c sample application and clarification to the doxygen documentation of the ECDSA functions involved.
273 lines
10 KiB
C
273 lines
10 KiB
C
/**
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* \file ecdsa.h
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*
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* \brief Elliptic curve DSA
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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#ifndef MBEDTLS_ECDSA_H
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#define MBEDTLS_ECDSA_H
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#include "ecp.h"
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#include "md.h"
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/*
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* RFC 4492 page 20:
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*
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* Ecdsa-Sig-Value ::= SEQUENCE {
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* r INTEGER,
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* s INTEGER
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* }
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*
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* Size is at most
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* 1 (tag) + 1 (len) + 1 (initial 0) + ECP_MAX_BYTES for each of r and s,
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* twice that + 1 (tag) + 2 (len) for the sequence
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* (assuming ECP_MAX_BYTES is less than 126 for r and s,
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* and less than 124 (total len <= 255) for the sequence)
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*/
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#if MBEDTLS_ECP_MAX_BYTES > 124
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#error "MBEDTLS_ECP_MAX_BYTES bigger than expected, please fix MBEDTLS_ECDSA_MAX_LEN"
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#endif
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/** Maximum size of an ECDSA signature in bytes */
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#define MBEDTLS_ECDSA_MAX_LEN ( 3 + 2 * ( 3 + MBEDTLS_ECP_MAX_BYTES ) )
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/**
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* \brief ECDSA context structure
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*/
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typedef mbedtls_ecp_keypair mbedtls_ecdsa_context;
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* \brief Compute ECDSA signature of a previously hashed message
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*
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* \note The deterministic version is usually prefered.
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*
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* \param grp ECP group
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* \param r First output integer
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* \param s Second output integer
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* \param d Private signing key
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* \param buf Message hash
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* \param blen Length of buf
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* \param f_rng RNG function
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* \param p_rng RNG parameter
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
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*/
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int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
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const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
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#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
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/**
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* \brief Compute ECDSA signature of a previously hashed message,
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* deterministic version (RFC 6979).
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*
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* \param grp ECP group
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* \param r First output integer
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* \param s Second output integer
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* \param d Private signing key
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* \param buf Message hash
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* \param blen Length of buf
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* \param md_alg MD algorithm used to hash the message
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
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*/
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int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
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const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
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mbedtls_md_type_t md_alg );
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#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
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/**
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* \brief Verify ECDSA signature of a previously hashed message
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*
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* \param grp ECP group
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* \param buf Message hash
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* \param blen Length of buf
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* \param Q Public key to use for verification
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* \param r First integer of the signature
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* \param s Second integer of the signature
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.4 step 3.
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*
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* \return 0 if successful,
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* MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid
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* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
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*/
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int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
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const unsigned char *buf, size_t blen,
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const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s);
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/**
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* \brief Compute ECDSA signature and write it to buffer,
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* serialized as defined in RFC 4492 page 20.
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* (Not thread-safe to use same context in multiple threads)
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*
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* \note The deterministic version (RFC 6979) is used if
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* MBEDTLS_ECDSA_DETERMINISTIC is defined.
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*
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* \param ctx ECDSA context
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* \param md_alg Algorithm that was used to hash the message
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* \param hash Message hash
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* \param hlen Length of hash
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* \param sig Buffer that will hold the signature
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* \param slen Length of the signature written
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* \param f_rng RNG function
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* \param p_rng RNG parameter
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*
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* \note The "sig" buffer must be at least as large as twice the
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* size of the curve used, plus 9 (eg. 73 bytes if a 256-bit
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* curve is used). MBEDTLS_ECDSA_MAX_LEN is always safe.
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a MBEDTLS_ERR_ECP_XXX, MBEDTLS_ERR_MPI_XXX or
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* MBEDTLS_ERR_ASN1_XXX error code
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*/
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int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg,
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const unsigned char *hash, size_t hlen,
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unsigned char *sig, size_t *slen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
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#if ! defined(MBEDTLS_DEPRECATED_REMOVED)
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#if defined(MBEDTLS_DEPRECATED_WARNING)
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#define MBEDTLS_DEPRECATED __attribute__((deprecated))
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#else
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#define MBEDTLS_DEPRECATED
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#endif
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/**
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* \brief Compute ECDSA signature and write it to buffer,
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* serialized as defined in RFC 4492 page 20.
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* Deterministic version, RFC 6979.
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* (Not thread-safe to use same context in multiple threads)
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*
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* \deprecated Superseded by mbedtls_ecdsa_write_signature() in 2.0.0
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*
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* \param ctx ECDSA context
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* \param hash Message hash
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* \param hlen Length of hash
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* \param sig Buffer that will hold the signature
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* \param slen Length of the signature written
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* \param md_alg MD algorithm used to hash the message
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*
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* \note The "sig" buffer must be at least as large as twice the
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* size of the curve used, plus 9 (eg. 73 bytes if a 256-bit
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* curve is used). MBEDTLS_ECDSA_MAX_LEN is always safe.
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a MBEDTLS_ERR_ECP_XXX, MBEDTLS_ERR_MPI_XXX or
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* MBEDTLS_ERR_ASN1_XXX error code
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*/
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int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
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const unsigned char *hash, size_t hlen,
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unsigned char *sig, size_t *slen,
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mbedtls_md_type_t md_alg ) MBEDTLS_DEPRECATED;
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#undef MBEDTLS_DEPRECATED
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#endif /* MBEDTLS_DEPRECATED_REMOVED */
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#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
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/**
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* \brief Read and verify an ECDSA signature
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*
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* \param ctx ECDSA context
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* \param hash Message hash
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* \param hlen Size of hash
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* \param sig Signature to read and verify
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* \param slen Size of sig
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.4 step 3.
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*
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* \return 0 if successful,
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* MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid,
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* MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if the signature is
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* valid but its actual length is less than siglen,
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* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_ERR_MPI_XXX error code
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*/
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int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,
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const unsigned char *hash, size_t hlen,
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const unsigned char *sig, size_t slen );
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/**
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* \brief Generate an ECDSA keypair on the given curve
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*
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* \param ctx ECDSA context in which the keypair should be stored
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* \param gid Group (elliptic curve) to use. One of the various
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* MBEDTLS_ECP_DP_XXX macros depending on configuration.
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* \param f_rng RNG function
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* \param p_rng RNG parameter
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*
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* \return 0 on success, or a MBEDTLS_ERR_ECP_XXX code.
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*/
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int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
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/**
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* \brief Set an ECDSA context from an EC key pair
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*
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* \param ctx ECDSA context to set
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* \param key EC key to use
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*
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* \return 0 on success, or a MBEDTLS_ERR_ECP_XXX code.
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*/
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int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key );
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/**
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* \brief Initialize context
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*
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* \param ctx Context to initialize
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*/
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void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx );
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/**
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* \brief Free context
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*
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* \param ctx Context to free
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*/
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void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx );
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#ifdef __cplusplus
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}
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#endif
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#endif /* ecdsa.h */
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