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