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Added ecp_check_pubkey().

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Manuel Pégourié-Gonnard 2012-11-24 12:05:44 +01:00 committed by Paul Bakker
parent c554e9acf1
commit 1c33057a63
4 changed files with 123 additions and 0 deletions
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19
include/polarssl/ecp.h
View file

@ -158,6 +158,25 @@ int ecp_set_zero( ecp_point *pt );
*/
int ecp_copy( ecp_point *P, const ecp_point *Q );
/**
* \brief Check that a point is a valid public key on this curve
*
* \param grp Curve/group the point should belong to
* \param pt Point to check
*
* \return 0 if point is a valid public key,
* POLARSSL_ERR_ECP_GENERIC otherwise.
*
* \note This function only checks the point is non-zero, has valid
* coordinates and lies on the curve, but not that it is
* indeed a multiple of G. This is additional check is more
* expensive, isn't required by standards, and shouldn't be
* necessary if the group used has a small cofactor. In
* particular, it is useless for the NIST groups which all
* have a cofactor of 1.
*/
int ecp_check_pubkey( const ecp_group *grp, const ecp_point *pt );
/**
* \brief Import a non-zero point from two ASCII strings
*

45
library/ecp.c
View file

@ -467,6 +467,51 @@ int ecp_use_known_dp( ecp_group *grp, size_t index )
while( mpi_cmp_mpi( &N, &grp->P ) >= 0 ) \
MPI_CHK( mpi_sub_mpi( &N, &N, &grp->P ) )
/*
* Check that a point is valid as a public key (SEC1 3.2.3.1)
*/
int ecp_check_pubkey( const ecp_group *grp, const ecp_point *pt )
{
int ret;
mpi YY, RHS;
if( mpi_cmp_int( &pt->Z, 0 ) == 0 )
return( POLARSSL_ERR_ECP_GENERIC );
/*
* pt coordinates must be normalized for our checks
*/
if( mpi_cmp_int( &pt->Z, 1 ) != 0 )
return( POLARSSL_ERR_ECP_GENERIC );
if( mpi_cmp_int( &pt->X, 0 ) < 0 ||
mpi_cmp_int( &pt->Y, 0 ) < 0 ||
mpi_cmp_mpi( &pt->X, &grp->P ) >= 0 ||
mpi_cmp_mpi( &pt->Y, &grp->P ) >= 0 )
return( POLARSSL_ERR_ECP_GENERIC );
mpi_init( &YY ); mpi_init( &RHS );
/*
* YY = Y^2
* RHS = X (X^2 - 3) + B = X^3 - 3X + B
*/
MPI_CHK( mpi_mul_mpi( &YY, &pt->Y, &pt->Y ) ); MOD_MUL( YY );
MPI_CHK( mpi_mul_mpi( &RHS, &pt->X, &pt->X ) ); MOD_MUL( RHS );
MPI_CHK( mpi_sub_int( &RHS, &RHS, 3 ) ); MOD_SUB( RHS );
MPI_CHK( mpi_mul_mpi( &RHS, &RHS, &pt->X ) ); MOD_MUL( RHS );
MPI_CHK( mpi_add_mpi( &RHS, &RHS, &grp->B ) ); MOD_ADD( RHS );
if( mpi_cmp_mpi( &YY, &RHS ) != 0 )
ret = POLARSSL_ERR_ECP_GENERIC;
cleanup:
mpi_free( &YY ); mpi_free( &RHS );
return( ret );
}
/*
* Normalize jacobian coordinates so that Z == 0 || Z == 1 (GECC 3.2.1)
*/

30
tests/suites/test_suite_ecp.data
View file

@ -103,6 +103,36 @@ ecp_small_mul:2:0:20:01:0
ECP small multiplication too big
ecp_small_mul:-1:0:0:0:POLARSSL_ERR_ECP_GENERIC
ECP small check pubkey #1
ecp_small_check_pub:1:1:0:POLARSSL_ERR_ECP_GENERIC
ECP small check pubkey #2
ecp_small_check_pub:9:-1:1:POLARSSL_ERR_ECP_GENERIC
ECP small check pubkey #3
ecp_small_check_pub:9:46:1:0
ECP small check pubkey #4
ecp_small_check_pub:13:47:1:POLARSSL_ERR_ECP_GENERIC
ECP small check pubkey #5
ecp_small_check_pub:13:0:1:0
ECP small check pubkey #6
ecp_small_check_pub:-1:10:1:POLARSSL_ERR_ECP_GENERIC
ECP small check pubkey #7
ecp_small_check_pub:46:10:1:0
ECP small check pubkey #8
ecp_small_check_pub:47:2:1:POLARSSL_ERR_ECP_GENERIC
ECP small check pubkey #9
ecp_small_check_pub:0:2:1:0
ECP small check pubkey #10
ecp_small_check_pub:10:25:1:POLARSSL_ERR_ECP_GENERIC
ECP mod p192 readable
ecp_fast_mod:SECP192R1:"000000000000010500000000000001040000000000000103000000000000010200000000000001010000000000000100"

29
tests/suites/test_suite_ecp.function
View file

@ -122,6 +122,29 @@ ecp_small_mul:m:r_zero:x_r:y_r:ret
}
END_CASE
BEGIN_CASE
ecp_small_check_pub:x:y:z:ret
{
ecp_group grp;
ecp_point P;
ecp_group_init( &grp );
ecp_point_init( &P );
TEST_ASSERT( ecp_group_read_string( &grp, 10,
"47", "4", "17", "42", "13" ) == 0 );
TEST_ASSERT( mpi_lset( &P.X, {x} ) == 0 );
TEST_ASSERT( mpi_lset( &P.Y, {y} ) == 0 );
TEST_ASSERT( mpi_lset( &P.Z, {z} ) == 0 );
TEST_ASSERT( ecp_check_pubkey( &grp, &P ) == {ret} );
ecp_group_free( &grp );
ecp_point_free( &P );
}
END_CASE
BEGIN_CASE
ecp_test_vect:id:dA:xA:yA:dB:xB:yB:xZ:yZ
{
@ -135,6 +158,8 @@ ecp_test_vect:id:dA:xA:yA:dB:xB:yB:xZ:yZ
TEST_ASSERT( ecp_use_known_dp( &grp, POLARSSL_ECP_DP_{id} ) == 0 );
TEST_ASSERT( ecp_check_pubkey( &grp, &grp.G ) == 0 );
TEST_ASSERT( mpi_read_string( &dA, 16, {dA} ) == 0 );
TEST_ASSERT( mpi_read_string( &xA, 16, {xA} ) == 0 );
TEST_ASSERT( mpi_read_string( &yA, 16, {yA} ) == 0 );
@ -147,16 +172,20 @@ ecp_test_vect:id:dA:xA:yA:dB:xB:yB:xZ:yZ
TEST_ASSERT( ecp_mul( &grp, &R, &dA, &grp.G ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.X, &xA ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.Y, &yA ) == 0 );
TEST_ASSERT( ecp_check_pubkey( &grp, &R ) == 0 );
TEST_ASSERT( ecp_mul( &grp, &R, &dB, &R ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.X, &xZ ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.Y, &yZ ) == 0 );
TEST_ASSERT( ecp_check_pubkey( &grp, &R ) == 0 );
TEST_ASSERT( ecp_mul( &grp, &R, &dB, &grp.G ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.X, &xB ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.Y, &yB ) == 0 );
TEST_ASSERT( ecp_check_pubkey( &grp, &R ) == 0 );
TEST_ASSERT( ecp_mul( &grp, &R, &dA, &R ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.X, &xZ ) == 0 );
TEST_ASSERT( mpi_cmp_mpi( &R.Y, &yZ ) == 0 );
TEST_ASSERT( ecp_check_pubkey( &grp, &R ) == 0 );
ecp_group_free( &grp ); ecp_point_free( &R );
mpi_free( &dA ); mpi_free( &xA ); mpi_free( &yA ); mpi_free( &dB );