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Added support for writing points compressed

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This commit is contained in:
Manuel Pégourié-Gonnard
2012-11-24 15:19:55 +01:00
committed by Paul Bakker
parent e19feb5b46
commit 37d218a8e3
4 changed files with 66 additions and 23 deletions
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36
library/ecp.c
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@ -174,16 +174,20 @@ cleanup:
}
/*
* Export a point into unsigned binary data, uncompressed format (SEC1 2.3.3)
* Export a point into unsigned binary data (SEC1 2.3.3)
*/
int ecp_write_binary( const ecp_group *grp, const ecp_point *P,
int ecp_write_binary( const ecp_group *grp, const ecp_point *P, int format,
size_t *olen, unsigned char *buf, size_t buflen )
{
int ret;
size_t plen;
if( format != POLARSSL_ECP_PF_UNCOMPRESSED &&
format != POLARSSL_ECP_PF_COMPRESSED )
return( POLARSSL_ERR_ECP_GENERIC );
/*
* Case P == 0
* Common case: P == 0
*/
if( mpi_cmp_int( &P->Z, 0 ) == 0 )
{
@ -197,14 +201,28 @@ int ecp_write_binary( const ecp_group *grp, const ecp_point *P,
}
plen = mpi_size( &grp->P );
*olen = 2 * plen + 1;
if( buflen < *olen )
return( POLARSSL_ERR_ECP_GENERIC );
if( format == POLARSSL_ECP_PF_UNCOMPRESSED )
{
*olen = 2 * plen + 1;
buf[0] = 0x04;
MPI_CHK( mpi_write_binary( &P->X, buf + 1, plen ) );
MPI_CHK( mpi_write_binary( &P->Y, buf + 1 + plen, plen ) );
if( buflen < *olen )
return( POLARSSL_ERR_ECP_GENERIC );
buf[0] = 0x04;
MPI_CHK( mpi_write_binary( &P->X, buf + 1, plen ) );
MPI_CHK( mpi_write_binary( &P->Y, buf + 1 + plen, plen ) );
}
else if( format == POLARSSL_ECP_PF_COMPRESSED )
{
*olen = plen + 1;
if( buflen < *olen )
return( POLARSSL_ERR_ECP_GENERIC );
buf[0] = 0x02 + mpi_get_bit( &P->Y, 0 );
MPI_CHK( mpi_write_binary( &P->X, buf + 1, plen ) );
}
cleanup:
return( ret );