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Use a more compact encoding of bad points

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Base 10 is horrible, base 256 is much better.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard
2021-06-23 12:25:48 +02:00
committed by Janos Follath
parent 6a5f5745d0
commit 10b8e5a5c9
2 changed files with 37 additions and 11 deletions
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27
library/ecp_curves.c
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@@ -81,6 +81,11 @@
#endif /* bits in mbedtls_mpi_uint */
#define ECP_MPI_INIT(s, n, p) {s, (n), (mbedtls_mpi_uint *)(p)}
#define ECP_MPI_INIT_ARRAY(x) \
ECP_MPI_INIT(1, sizeof(x) / sizeof(mbedtls_mpi_uint), x)
/*
* Note: the constants are in little-endian order
* to be directly usable in MPIs
@@ -716,6 +721,28 @@ cleanup:
return( ret );
}
/*
* Constants for the two points other than 0, 1, -1 (mod p) in
* https://cr.yp.to/ecdh.html#validate
* See ecp_check_pubkey_x25519().
*/
static const mbedtls_mpi_uint x25519_bad_point_1[] = {
BYTES_TO_T_UINT_8( 0xe0, 0xeb, 0x7a, 0x7c, 0x3b, 0x41, 0xb8, 0xae ),
BYTES_TO_T_UINT_8( 0x16, 0x56, 0xe3, 0xfa, 0xf1, 0x9f, 0xc4, 0x6a ),
BYTES_TO_T_UINT_8( 0xda, 0x09, 0x8d, 0xeb, 0x9c, 0x32, 0xb1, 0xfd ),
BYTES_TO_T_UINT_8( 0x86, 0x62, 0x05, 0x16, 0x5f, 0x49, 0xb8, 0x00 ),
};
static const mbedtls_mpi_uint x25519_bad_point_2[] = {
BYTES_TO_T_UINT_8( 0x5f, 0x9c, 0x95, 0xbc, 0xa3, 0x50, 0x8c, 0x24 ),
BYTES_TO_T_UINT_8( 0xb1, 0xd0, 0xb1, 0x55, 0x9c, 0x83, 0xef, 0x5b ),
BYTES_TO_T_UINT_8( 0x04, 0x44, 0x5c, 0xc4, 0x58, 0x1c, 0x8e, 0x86 ),
BYTES_TO_T_UINT_8( 0xd8, 0x22, 0x4e, 0xdd, 0xd0, 0x9f, 0x11, 0x57 ),
};
const mbedtls_mpi mbedtls_ecp_x25519_bad_point_1 = ECP_MPI_INIT_ARRAY(
x25519_bad_point_1 );
const mbedtls_mpi mbedtls_ecp_x25519_bad_point_2 = ECP_MPI_INIT_ARRAY(
x25519_bad_point_2 );
#endif /* MBEDTLS_ECP_DP_CURVE25519_ENABLED */
#if defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)