static void
sign(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_secret_key *skey )
{
gcry_mpi_t k;
gcry_mpi_t t = mpi_alloc( mpi_get_nlimbs(a) );
gcry_mpi_t inv = mpi_alloc( mpi_get_nlimbs(a) );
gcry_mpi_t p_1 = mpi_copy(skey->p);
/*
* b = (t * inv) mod (p-1)
* b = (t * inv(k,(p-1),(p-1)) mod (p-1)
* b = (((M-x*a) mod (p-1)) * inv(k,(p-1),(p-1))) mod (p-1)
*
*/
mpi_sub_ui(p_1, p_1, 1);
k = gen_k( skey->p, 0 /* no small K ! */ );
gcry_mpi_powm( a, skey->g, k, skey->p );
mpi_mul(t, skey->x, a );
mpi_subm(t, input, t, p_1 );
mpi_invm(inv, k, p_1 );
mpi_mulm(b, t, inv, p_1 );
#if 0
if( DBG_CIPHER )
{
log_mpidump("elg sign p= ", skey->p);
log_mpidump("elg sign g= ", skey->g);
log_mpidump("elg sign y= ", skey->y);
log_mpidump("elg sign x= ", skey->x);
log_mpidump("elg sign k= ", k);
log_mpidump("elg sign M= ", input);
log_mpidump("elg sign a= ", a);
log_mpidump("elg sign b= ", b);
}
#endif
mpi_free(k);
mpi_free(t);
mpi_free(inv);
mpi_free(p_1);
}
static void
ec_subm (gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, mpi_ec_t ctx)
{
mpi_subm (w, u, v, ctx->p);
}