mirror of
https://github.com/yuzu-emu/mbedtls.git
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231 lines
5.7 KiB
C
231 lines
5.7 KiB
C
/*
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* Elliptic curve DSA
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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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/*
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* References:
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*
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* SEC1 http://www.secg.org/index.php?action=secg,docs_secg
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*/
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#include "polarssl/config.h"
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#if defined(POLARSSL_ECDSA_C)
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#include "polarssl/ecdsa.h"
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/*
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* Derive a suitable integer for group grp from a buffer of length len
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* SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3
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*/
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static int derive_mpi( const ecp_group *grp, mpi *x,
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const unsigned char *buf, size_t blen )
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{
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size_t n_size = (grp->nbits + 7) / 8;
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return( mpi_read_binary( x, buf, blen > n_size ? n_size : blen ) );
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}
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/*
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* Compute ECDSA signature of a hashed message (SEC1 4.1.3)
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* Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
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*/
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int ecdsa_sign( const ecp_group *grp, mpi *r, mpi *s,
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const 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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{
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int ret, key_tries, sign_tries;
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ecp_point R;
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mpi k, e;
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ecp_point_init( &R );
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mpi_init( &k );
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mpi_init( &e );
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sign_tries = 0;
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do
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{
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/*
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* Steps 1-3: generate a suitable ephemeral keypair
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*/
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key_tries = 0;
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do
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{
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MPI_CHK( ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) );
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MPI_CHK( mpi_copy( r, &R.X ) );
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if( key_tries++ > 10 )
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{
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ret = POLARSSL_ERR_ECP_GENERIC;
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goto cleanup;
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}
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}
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while( mpi_cmp_int( r, 0 ) == 0 );
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/*
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* Step 5: derive MPI from hashed message
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*/
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MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
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/*
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* Step 6: compute s = (e + r * d) / k mod n
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*/
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MPI_CHK( mpi_mul_mpi( s, r, d ) );
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MPI_CHK( mpi_add_mpi( &e, &e, s ) );
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MPI_CHK( mpi_inv_mod( s, &k, &grp->N ) );
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MPI_CHK( mpi_mul_mpi( s, s, &e ) );
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MPI_CHK( mpi_mod_mpi( s, s, &grp->N ) );
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if( sign_tries++ > 10 )
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{
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ret = POLARSSL_ERR_ECP_GENERIC;
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goto cleanup;
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}
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}
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while( mpi_cmp_int( s, 0 ) == 0 );
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cleanup:
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ecp_point_free( &R );
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mpi_free( &k );
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mpi_free( &e );
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return( ret );
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}
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/*
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* Verify ECDSA signature of hashed message (SEC1 4.1.4)
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* Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
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*/
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int ecdsa_verify( const ecp_group *grp,
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const unsigned char *buf, size_t blen,
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const ecp_point *Q, const mpi *r, const mpi *s)
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{
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int ret;
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mpi e, s_inv, u1, u2;
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ecp_point R, P;
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ecp_point_init( &R ); ecp_point_init( &P );
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mpi_init( &e ); mpi_init( &s_inv ); mpi_init( &u1 ); mpi_init( &u2 );
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/*
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* Step 1: make sure r and s are in range 1..n-1
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*/
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if( mpi_cmp_int( r, 1 ) < 0 || mpi_cmp_mpi( r, &grp->N ) >= 0 ||
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mpi_cmp_int( s, 1 ) < 0 || mpi_cmp_mpi( s, &grp->N ) >= 0 )
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{
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ret = POLARSSL_ERR_ECP_BAD_INPUT_DATA;
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goto cleanup;
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}
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/*
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* Additional precaution: make sure Q is valid
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*/
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MPI_CHK( ecp_check_pubkey( grp, Q ) );
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/*
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* Step 3: derive MPI from hashed message
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*/
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MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
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/*
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* Step 4: u1 = e / s mod n, u2 = r / s mod n
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*/
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MPI_CHK( mpi_inv_mod( &s_inv, s, &grp->N ) );
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MPI_CHK( mpi_mul_mpi( &u1, &e, &s_inv ) );
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MPI_CHK( mpi_mod_mpi( &u1, &u1, &grp->N ) );
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MPI_CHK( mpi_mul_mpi( &u2, r, &s_inv ) );
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MPI_CHK( mpi_mod_mpi( &u2, &u2, &grp->N ) );
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/*
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* Step 5: R = u1 G + u2 Q
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*/
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MPI_CHK( ecp_mul( grp, &R, &u1, &grp->G ) );
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MPI_CHK( ecp_mul( grp, &P, &u2, Q ) );
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MPI_CHK( ecp_add( grp, &R, &R, &P ) );
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if( ecp_is_zero( &R ) )
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{
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ret = POLARSSL_ERR_ECP_BAD_INPUT_DATA;
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goto cleanup;
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}
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/*
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* Step 6: check that xR == r
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*/
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if( mpi_cmp_mpi( &R.X, r ) != 0 )
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{
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ret = POLARSSL_ERR_ECP_BAD_INPUT_DATA;
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goto cleanup;
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}
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cleanup:
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ecp_point_free( &R ); ecp_point_free( &P );
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mpi_free( &e ); mpi_free( &s_inv ); mpi_free( &u1 ); mpi_free( &u2 );
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return( ret );
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}
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/*
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* Initialize context
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*/
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void ecdsa_init( ecdsa_context *ctx )
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{
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ecp_group_init( &ctx->grp );
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mpi_init( &ctx->d );
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ecp_point_init( &ctx->Q );
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mpi_init( &ctx->r );
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mpi_init( &ctx->s );
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mpi_init( &ctx->d );
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ctx->point_format = POLARSSL_ECP_PF_UNCOMPRESSED;
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}
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/*
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* Free context
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*/
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void ecdsa_free( ecdsa_context *ctx )
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{
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ecp_group_free( &ctx->grp );
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mpi_free( &ctx->d );
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ecp_point_free( &ctx->Q );
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mpi_free( &ctx->r );
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mpi_free( &ctx->s );
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mpi_free( &ctx->d );
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ctx->point_format = POLARSSL_ECP_PF_UNCOMPRESSED;
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}
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#if defined(POLARSSL_SELF_TEST)
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/*
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* Checkup routine
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*/
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int ecdsa_self_test( int verbose )
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{
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return( verbose++ );
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}
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#endif
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#endif /* defined(POLARSSL_ECDSA_C) */
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