Commit b309ab29 authored by Manuel Pégourié-Gonnard's avatar Manuel Pégourié-Gonnard
Browse files

Add ECDSA sign primitive

parent 2aea1416
......@@ -33,6 +33,25 @@
extern "C" {
#endif
/**
* \brief Compute ECDSA signature of a previously hashed message
*
* \param grp ECP group
* \param r First output integer
* \param s Second output integer
* \param d Private signing key
* \param buf Message hash
* \param blen Length of buf
* \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 ecdsa_sign( const ecp_group *grp, mpi *r, mpi *s,
const mpi *d, const unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
/**
* \brief Checkup routine
*
......
......@@ -35,6 +35,67 @@
#include "polarssl/ecdsa.h"
/*
* Compute ECDSA signature of a hashed message (SEC1 4.1.3)
* Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
*/
int ecdsa_sign( const ecp_group *grp, mpi *r, mpi *s,
const mpi *d, const unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
{
int ret, key_tries, sign_tries;
size_t n_size;
ecp_point R;
mpi k, e;
ecp_point_init( &R );
mpi_init( &k );
mpi_init( &e );
sign_tries = 0;
do
{
/*
* Steps 1-3: generate a suitable ephemeral keypair
*/
key_tries = 0;
do
{
MPI_CHK( ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) );
MPI_CHK( mpi_copy( r, &R.X ) );
if( key_tries++ > 10 )
return( POLARSSL_ERR_ECP_GENERIC );
}
while( mpi_cmp_int( r, 0 ) == 0 );
/*
* Step 5: derive MPI from hashed message
*/
n_size = (grp->nbits + 7) / 8;
MPI_CHK( mpi_read_binary( &e, buf, blen > n_size ? n_size : blen ) );
/*
* Step 6: compute s = (e + r * d) / k mod n
*/
MPI_CHK( mpi_mul_mpi( s, r, d ) );
MPI_CHK( mpi_add_mpi( &e, &e, s ) );
MPI_CHK( mpi_inv_mod( s, &k, &grp->N ) );
MPI_CHK( mpi_mul_mpi( s, s, &e ) );
MPI_CHK( mpi_mod_mpi( s, s, &grp->N ) );
if( sign_tries++ > 10 )
return( POLARSSL_ERR_ECP_GENERIC );
}
while( mpi_cmp_int( s, 0 ) == 0 );
cleanup:
ecp_point_free( &R );
mpi_free( &k );
mpi_free( &e );
return( ret );
}
#if defined(POLARSSL_SELF_TEST)
......
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