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Add Montgomery points to ecp_point_read_binary

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The library is able to perform computations and cryptographic schemes on
curves with x coordinate ladder representation. Here we add the
capability to import such points.
This commit is contained in:
Janos Follath 2019-02-13 10:44:06 +00:00
parent a778a94b7d
commit 59b813c7be
3 changed files with 65 additions and 17 deletions
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29
library/ecp.c
View file

@ -788,7 +788,7 @@ cleanup:
}
/*
* Import a point from unsigned binary data (SEC1 2.3.4)
* Import a point from unsigned binary data (SEC1 2.3.4 and RFC7748)
*/
int mbedtls_ecp_point_read_binary( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *pt,
@ -803,6 +803,25 @@ int mbedtls_ecp_point_read_binary( const mbedtls_ecp_group *grp,
if( ilen < 1 )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
plen = mbedtls_mpi_size( &grp->P );
#if defined(ECP_MONTGOMERY)
if( ecp_get_type( grp ) == ECP_TYPE_MONTGOMERY )
{
if( plen != ilen )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary_le( &pt->X, buf, plen ) );
mbedtls_mpi_free( &pt->Y );
if( grp->id == MBEDTLS_ECP_DP_CURVE25519 )
/* Set most significant bit to 0 */
MBEDTLS_MPI_CHK( mbedtls_mpi_set_bit( &pt->X, plen * 8 - 1, 0 ) );
}
#endif
#if defined(ECP_SHORTWEIERSTRASS)
if( ecp_get_type( grp ) != ECP_TYPE_MONTGOMERY )
{
if( buf[0] == 0x00 )
{
if( ilen == 1 )
@ -811,8 +830,6 @@ int mbedtls_ecp_point_read_binary( const mbedtls_ecp_group *grp,
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
}
plen = mbedtls_mpi_size( &grp->P );
if( buf[0] != 0x04 )
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
@ -820,7 +837,11 @@ int mbedtls_ecp_point_read_binary( const mbedtls_ecp_group *grp,
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->X, buf + 1, plen ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->Y, buf + 1 + plen, plen ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->Y,
buf + 1 + plen, plen ) );
}
#endif
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &pt->Z, 1 ) );
cleanup:

12
tests/suites/test_suite_ecp.data
View file

@ -112,6 +112,18 @@ ECP read binary #6 (non-zero, OK)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
ecp_read_binary:MBEDTLS_ECP_DP_SECP192R1:"0448d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc99336ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":"48d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":"6ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":"01":0
ECP read binary #7 (Montgomery, OK)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_read_binary:MBEDTLS_ECP_DP_CURVE25519:"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a":"6a4e9baa8ea9a4ebf41a38260d3abf0d5af73eb4dc7d8b7454a7308909f02085":"0":"1":0
ECP read binary #8 (Montgomery, masked first bit)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_read_binary:MBEDTLS_ECP_DP_CURVE25519:"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4efa":"7a4e9baa8ea9a4ebf41a38260d3abf0d5af73eb4dc7d8b7454a7308909f02085":"0":"1":0
ECP read binary #9 (Montgomery, invalid length)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_read_binary:MBEDTLS_ECP_DP_CURVE25519:"20f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a":"6a4e9baa8ea9a4ebf41a38260d3abf0d5af73eb4dc7d8b7454a7308909f020":"0":"1":MBEDTLS_ERR_ECP_BAD_INPUT_DATA
ECP tls read point #1 (zero, invalid length byte)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
mbedtls_ecp_tls_read_point:MBEDTLS_ECP_DP_SECP192R1:"0200":"01":"01":"00":MBEDTLS_ERR_ECP_BAD_INPUT_DATA

15
tests/suites/test_suite_ecp.function
View file

@ -760,9 +760,24 @@ void ecp_read_binary( int id, data_t * buf, char * x, char * y, char * z,
if( ret == 0 )
{
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &P.X, &X ) == 0 );
/*
* At the time of writing, the following condition is equivalent with
* if( ecp_get_type( grp ) == ECP_TYPE_MONTGOMERY )
* but has the advantage of not using internal symbols.
*/
if( grp.G.Y.p == NULL )
{
TEST_ASSERT( mbedtls_mpi_cmp_int( &Y, 0 ) == 0 );
TEST_ASSERT( P.Y.p == NULL );
TEST_ASSERT( mbedtls_mpi_cmp_int( &Z, 1 ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_int( &P.Z, 1 ) == 0 );
}
else
{
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &P.Y, &Y ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &P.Z, &Z ) == 0 );
}
}
exit:
mbedtls_ecp_group_free( &grp ); mbedtls_ecp_point_free( &P );