ECP self test: add self-test step for Montgomery curves
Run some self-test both for a short Weierstrass curve and for a
Montgomery curve, if the build-time configuration includes a curve of
both types. Run both because there are significant differences in the
implementation.
The test data is suitable for Curve25519.
Signed-off-by: Gilles Peskine <gilles.peskine@arm.com>
diff --git a/library/ecp.c b/library/ecp.c
index 1f7943aa..519c50a 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -3301,7 +3301,7 @@
size_t n_exponents )
{
int ret = 0;
- size_t i;
+ size_t i = 0;
unsigned long add_c_prev, dbl_c_prev, mul_c_prev;
add_count = 0;
dbl_count = 0;
@@ -3350,10 +3350,12 @@
mbedtls_ecp_group grp;
mbedtls_ecp_point R, P;
mbedtls_mpi m;
+
+#if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
/* Exponents especially adapted for secp192k1, which has the lowest
* order n of all supported curves (secp192r1 is in a slightly larger
* field but the order of its base point is slightly smaller). */
- const char *exponents[] =
+ const char *sw_exponents[] =
{
"000000000000000000000000000000000000000000000001", /* one */
"FFFFFFFFFFFFFFFFFFFFFFFE26F2FC170F69466A74DEFD8C", /* n - 1 */
@@ -3362,12 +3364,25 @@
"7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", /* all ones */
"555555555555555555555555555555555555555555555555", /* 101010... */
};
+#endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
+#if defined(MBEDTLS_ECP_MONTGOMERY_ENABLED)
+ const char *m_exponents[] =
+ {
+ "4000000000000000000000000000000000000000000000000000000000000000",
+ "5C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C3C30",
+ "5715ECCE24583F7A7023C24164390586842E816D7280A49EF6DF4EAE6B280BF8",
+ "41A2B017516F6D254E1F002BCCBADD54BE30F8CEC737A0E912B4963B6BA74460",
+ "5555555555555555555555555555555555555555555555555555555555555550",
+ "7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF8",
+ };
+#endif /* MBEDTLS_ECP_MONTGOMERY_ENABLED */
mbedtls_ecp_group_init( &grp );
mbedtls_ecp_point_init( &R );
mbedtls_ecp_point_init( &P );
mbedtls_mpi_init( &m );
+#if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
/* Use secp192r1 if available, or any available curve */
#if defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED)
MBEDTLS_MPI_CHK( mbedtls_ecp_group_load( &grp, MBEDTLS_ECP_DP_SECP192R1 ) );
@@ -3376,24 +3391,48 @@
#endif
if( verbose != 0 )
- mbedtls_printf( " ECP test #1 (constant op_count, base point G): " );
+ mbedtls_printf( " ECP SW test #1 (constant op_count, base point G): " );
/* Do a dummy multiplication first to trigger precomputation */
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &m, 2 ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_mul( &grp, &P, &m, &grp.G, NULL, NULL ) );
ret = self_test_point( verbose,
&grp, &R, &m, &grp.G,
- exponents,
- sizeof( exponents ) / sizeof( exponents[0] ));
+ sw_exponents,
+ sizeof( sw_exponents ) / sizeof( sw_exponents[0] ));
if( ret != 0 )
goto cleanup;
if( verbose != 0 )
- mbedtls_printf( " ECP test #2 (constant op_count, other point): " );
+ mbedtls_printf( " ECP SW test #2 (constant op_count, other point): " );
/* We computed P = 2G last time, use it */
ret = self_test_point( verbose,
&grp, &R, &m, &P,
- exponents,
- sizeof( exponents ) / sizeof( exponents[0] ));
+ sw_exponents,
+ sizeof( sw_exponents ) / sizeof( sw_exponents[0] ));
+ if( ret != 0 )
+ goto cleanup;
+
+ mbedtls_ecp_group_free( &grp );
+ mbedtls_ecp_point_free( &R );
+#endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
+
+#if defined(MBEDTLS_ECP_MONTGOMERY_ENABLED)
+ if( verbose != 0 )
+ mbedtls_printf( " ECP Montgomery test (constant op_count): " );
+#if defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED)
+ MBEDTLS_MPI_CHK( mbedtls_ecp_group_load( &grp, MBEDTLS_ECP_DP_CURVE25519 ) );
+#elif defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
+ MBEDTLS_MPI_CHK( mbedtls_ecp_group_load( &grp, MBEDTLS_ECP_DP_CURVE448 ) );
+#else
+#error "MBEDTLS_ECP_MONTGOMERY_ENABLED is defined, but no curve is supported for self-test"
+#endif
+ ret = self_test_point( verbose,
+ &grp, &R, &m, &grp.G,
+ m_exponents,
+ sizeof( m_exponents ) / sizeof( m_exponents[0] ));
+ if( ret != 0 )
+ goto cleanup;
+#endif /* MBEDTLS_ECP_MONTGOMERY_ENABLED */
cleanup: