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use MPI_ECP_* macros in mbedtls_ecp_sw_derive_y()

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Signed-off-by: Glenn Strauss <gstrauss@gluelogic.com>
This commit is contained in:
Glenn Strauss 2022-12-19 19:30:54 -05:00
parent cbfd5e9db7
commit fcabc28cfc
1 changed files with 5 additions and 9 deletions
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14
library/ecp.c
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@ -793,19 +793,15 @@ static int mbedtls_ecp_sw_derive_y( const mbedtls_ecp_group *grp,
/* use Y to store intermediate results */
/* y^2 = x^3 + ax + b = (x^2 + a)x + b */
/* x^2 */
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( Y, X, X ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( Y, Y, &grp->P ) );
MPI_ECP_MUL( Y, X, X );
/* x^2 + a */
if( !grp->A.p ) /* special case for A = -3; temporarily set exp = -3 */
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &exp, -3 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( Y, Y, grp->A.p ? &grp->A : &exp ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( Y, Y, &grp->P ) );
MPI_ECP_LSET( &exp, -3 );
MPI_ECP_ADD( Y, Y, grp->A.p ? &grp->A : &exp );
/* (x^2 + a)x */
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( Y, Y, X ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( Y, Y, &grp->P ) );
MPI_ECP_MUL( Y, Y, X );
/* (x^2 + a)x + b */
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( Y, Y, &grp->B ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( Y, Y, &grp->P ) );
MPI_ECP_ADD( Y, Y, &grp->B );
/* w = y^2 */ /* Y contains y^2 intermediate result */
/* exp = ((p+1)/4) */