Allow T to be computed in multiple steps
Previously there were only two states:
- T unallocated
- T allocated and valid
Now there are three:
- T unallocated
- T allocated and in progress
- T allocated and valid
Introduce new bool T_ok to distinguish the last two states.
diff --git a/library/ecp.c b/library/ecp.c
index 653c60f..71fb314 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -113,6 +113,8 @@
unsigned char T_size; /* number of points in table T */
enum { /* what's the next step ? */
ecp_rs_init = 0, /* just getting started */
+ ecp_rs_tmp_dummy, /* temporary for incremental testing */
+ ecp_rs_T_done, /* call ecp_mul_comb_after_precomp() */
ecp_rs_final_norm, /* do the final normalization */
} state;
};
@@ -1334,6 +1336,15 @@
size_t j;
mbedtls_ecp_point *cur, *TT[COMB_MAX_PRE - 1];
+#if defined(MBEDTLS_ECP_EARLY_RETURN)
+ /* XXX: dummy "in_progress" return for testing caller */
+ if( grp->rs != NULL && grp->rs->state == ecp_rs_init )
+ {
+ grp->rs->state++;
+ return( MBEDTLS_ERR_ECP_IN_PROGRESS );
+ }
+#endif
+
/*
* Set T[0] = P and
* T[2^{l-1}] = 2^{dl} P for l = 1 .. w-1 (this is not the final value)
@@ -1370,6 +1381,11 @@
MBEDTLS_MPI_CHK( ecp_normalize_jac_many( grp, TT, k ) );
+#if defined(MBEDTLS_ECP_EARLY_RETURN)
+ if( grp->rs != NULL )
+ grp->rs->state++;
+#endif
+
cleanup:
return( ret );
@@ -1613,7 +1629,7 @@
int ret;
unsigned char w, p_eq_g = 0, i;
size_t d;
- unsigned char pre_len = 0;
+ unsigned char pre_len = 0, T_ok = 0;
mbedtls_ecp_point *T = NULL;
#if defined(MBEDTLS_ECP_EARLY_RETURN)
@@ -1657,22 +1673,28 @@
pre_len = 1U << ( w - 1 );
d = ( grp->nbits + w - 1 ) / w;
- /*
- * Prepare precomputed points: if P == G we want to
- * use grp->T if already initialized, or initialize it.
- */
- T = p_eq_g ? grp->T : NULL;
+ /* Pre-computed table: do we have it already for the base point? */
+ if( p_eq_g && grp->T != NULL )
+ {
+ T = grp->T;
+ T_ok = 1;
+ }
#if defined(MBEDTLS_ECP_EARLY_RETURN)
+ /* Pre-computed table: do we have one in progress? complete? */
if( grp->rs != NULL && grp->rs->T != NULL && T == NULL )
{
/* transfer "ownership" of T from rs to local function */
T = grp->rs->T;
grp->rs->T = NULL;
grp->rs->T_size = 0;
+
+ if( grp->rs->state >= ecp_rs_T_done )
+ T_ok = 1;
}
#endif
+ /* Allocate table if we didn't have any */
if( T == NULL )
{
T = mbedtls_calloc( pre_len, sizeof( mbedtls_ecp_point ) );
@@ -1681,7 +1703,11 @@
ret = MBEDTLS_ERR_ECP_ALLOC_FAILED;
goto cleanup;
}
+ }
+ /* Compute table (or finish computing it) if not done already */
+ if( !T_ok )
+ {
MBEDTLS_MPI_CHK( ecp_precompute_comb( grp, T, P, w, d ) );
if( p_eq_g )