225 lines
7.6 KiB
C
225 lines
7.6 KiB
C
/**
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* \file ecdh.h
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*
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* \brief Elliptic curve Diffie-Hellman
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*
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* Copyright (C) 2006-2013, Brainspark B.V.
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*
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* This file is part of PolarSSL (http://www.polarssl.org)
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* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef POLARSSL_ECDH_H
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#define POLARSSL_ECDH_H
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#include "ecp.h"
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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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* When importing from an EC key, select if it is our key or the peer's key
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*/
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typedef enum
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{
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POLARSSL_ECDH_OURS,
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POLARSSL_ECDH_THEIRS,
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} ecdh_side;
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/**
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* \brief ECDH context structure
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*/
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typedef struct
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{
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ecp_group grp; /*!< elliptic curve used */
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mpi d; /*!< our secret value (private key) */
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ecp_point Q; /*!< our public value (public key) */
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ecp_point Qp; /*!< peer's public value (public key) */
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mpi z; /*!< shared secret */
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int point_format; /*!< format for point export in TLS messages */
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ecp_point Vi; /*!< blinding value (for later) */
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ecp_point Vf; /*!< un-blinding value (for later) */
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mpi _d; /*!< previous d (for later) */
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}
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ecdh_context;
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/**
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* \brief Generate a public key.
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* Raw function that only does the core computation.
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*
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* \param grp ECP group
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* \param d Destination MPI (secret exponent, aka private key)
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* \param Q Destination point (public key)
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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 if successful,
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* or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
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*/
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int ecdh_gen_public( ecp_group *grp, mpi *d, ecp_point *Q,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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/**
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* \brief Compute shared secret
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* Raw function that only does the core computation.
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*
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* \param grp ECP group
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* \param z Destination MPI (shared secret)
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* \param Q Public key from other party
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* \param d Our secret exponent (private key)
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* \param f_rng RNG function (see notes)
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* \param p_rng RNG parameter
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*
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* \return 0 if successful,
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* or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
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*
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* \note If f_rng is not NULL, it is used to implement
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* countermeasures against potential elaborate timing
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* attacks, see \c ecp_mul() for details.
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*/
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int ecdh_compute_shared( ecp_group *grp, mpi *z,
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const ecp_point *Q, const mpi *d,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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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 ecdh_init( ecdh_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 ecdh_free( ecdh_context *ctx );
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/**
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* \brief Generate a public key and a TLS ServerKeyExchange payload.
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* (First function used by a TLS server for ECDHE.)
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*
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* \param ctx ECDH context
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* \param olen number of chars written
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* \param buf destination buffer
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* \param blen length of buffer
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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 This function assumes that ctx->grp has already been
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* properly set (for example using ecp_use_known_dp).
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*
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* \return 0 if successful, or an POLARSSL_ERR_ECP_XXX error code
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*/
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int ecdh_make_params( ecdh_context *ctx, size_t *olen,
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unsigned char *buf, size_t blen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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/**
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* \brief Parse and procress a TLS ServerKeyExhange payload.
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* (First function used by a TLS client for ECDHE.)
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*
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* \param ctx ECDH context
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* \param buf pointer to start of input buffer
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* \param end one past end of buffer
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*
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* \return 0 if successful, or an POLARSSL_ERR_ECP_XXX error code
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*/
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int ecdh_read_params( ecdh_context *ctx,
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const unsigned char **buf, const unsigned char *end );
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/**
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* \brief Setup an ECDH context from an EC key.
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* (Used by clients and servers in place of the
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* ServerKeyEchange for static ECDH: import ECDH parameters
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* from a certificate's EC key information.)
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*
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* \param ctx ECDH constext to set
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* \param key EC key to use
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* \param side Is it our key (1) or the peer's key (0) ?
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*
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* \return 0 if successful, or an POLARSSL_ERR_ECP_XXX error code
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*/
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int ecdh_get_params( ecdh_context *ctx, const ecp_keypair *key,
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ecdh_side side );
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/**
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* \brief Generate a public key and a TLS ClientKeyExchange payload.
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* (Second function used by a TLS client for ECDH(E).)
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*
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* \param ctx ECDH context
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* \param olen number of bytes actually written
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* \param buf destination buffer
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* \param blen size of destination buffer
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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 if successful, or an POLARSSL_ERR_ECP_XXX error code
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*/
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int ecdh_make_public( ecdh_context *ctx, size_t *olen,
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unsigned char *buf, size_t blen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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/**
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* \brief Parse and process a TLS ClientKeyExchange payload.
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* (Second function used by a TLS server for ECDH(E).)
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*
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* \param ctx ECDH context
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* \param buf start of input buffer
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* \param blen length of input buffer
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*
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* \return 0 if successful, or an POLARSSL_ERR_ECP_XXX error code
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*/
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int ecdh_read_public( ecdh_context *ctx,
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const unsigned char *buf, size_t blen );
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/**
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* \brief Derive and export the shared secret.
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* (Last function used by both TLS client en servers.)
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*
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* \param ctx ECDH context
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* \param olen number of bytes written
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* \param buf destination buffer
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* \param blen buffer length
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* \param f_rng RNG function, see notes for \c ecdh_compute_shared()
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* \param p_rng RNG parameter
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*
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* \return 0 if successful, or an POLARSSL_ERR_ECP_XXX error code
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*/
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int ecdh_calc_secret( ecdh_context *ctx, size_t *olen,
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unsigned char *buf, size_t blen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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/**
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* \brief Checkup routine
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*
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* \return 0 if successful, or 1 if the test failed
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*/
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int ecdh_self_test( int verbose );
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#ifdef __cplusplus
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}
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#endif
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#endif /* ecdh.h */
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