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ecp_curves: Hardcode Montgomery const for curve448.

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This patch adds two embedded constants used by `ecp_use_curve448()`.
The method has been updated to read that into an mpi instead of
calculating it on the fly.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This commit is contained in:
Minos Galanakis 2023-01-16 17:17:08 +00:00
parent bececeb0b9
commit 146fed9849
1 changed files with 25 additions and 20 deletions
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45
library/ecp_curves.c
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@ -4681,11 +4681,29 @@ cleanup:
#if defined(MBEDTLS_ECP_DP_CURVE448_ENABLED) #if defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
/* Constants used by ecp_use_curve448() */ /* Constants used by ecp_use_curve448() */
static const mbedtls_mpi_sint curve448_a24 = 0x98AA; static const mbedtls_mpi_sint curve448_a24 = 0x98AA;
static const unsigned char curve448_part_of_n[] = {
0x83, 0x35, 0xDC, 0x16, 0x3B, 0xB1, 0x24, /* P = 2^448 - 2^224 - 1 */
0xB6, 0x51, 0x29, 0xC9, 0x6F, 0xDE, 0x93, static const mbedtls_mpi_uint curve448_p[] = {
0x3D, 0x8D, 0x72, 0x3A, 0x70, 0xAA, 0xDC, MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
0x87, 0x3D, 0x6D, 0x54, 0xA7, 0xBB, 0x0D, MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFE, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0X00, 0X00, 0X00, 0X00, 0X00, 0X00, 0X00, 0X00)
};
/* N = 2^446 - 13818066809895115352007386748515426880336692474882178609894547503885 */
static const mbedtls_mpi_uint curve448_n[] = {
MBEDTLS_BYTES_TO_T_UINT_8(0XF3, 0X44, 0X58, 0XAB, 0X92, 0XC2, 0X78, 0X23),
MBEDTLS_BYTES_TO_T_UINT_8(0X55, 0X8F, 0XC5, 0X8D, 0X72, 0XC2, 0X6C, 0X21),
MBEDTLS_BYTES_TO_T_UINT_8(0X90, 0X36, 0XD6, 0XAE, 0X49, 0XDB, 0X4E, 0XC4),
MBEDTLS_BYTES_TO_T_UINT_8(0XE9, 0X23, 0XCA, 0X7C, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF),
MBEDTLS_BYTES_TO_T_UINT_8(0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF, 0X3F),
MBEDTLS_BYTES_TO_T_UINT_8(0X00, 0X00, 0X00, 0X00, 0X00, 0X00, 0X00, 0X00)
}; };
/* /*
@ -4693,20 +4711,12 @@ static const unsigned char curve448_part_of_n[] = {
*/ */
static int ecp_use_curve448(mbedtls_ecp_group *grp) static int ecp_use_curve448(mbedtls_ecp_group *grp)
{ {
mbedtls_mpi Ns;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi_init(&Ns);
/* Actually ( A + 2 ) / 4 */ /* Actually ( A + 2 ) / 4 */
MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&grp->A, curve448_a24)); MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&grp->A, curve448_a24));
/* P = 2^448 - 2^224 - 1 */ ecp_mpi_load(&grp->P, curve448_p, sizeof(curve448_p));
MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&grp->P, 1));
MBEDTLS_MPI_CHK(mbedtls_mpi_shift_l(&grp->P, 224));
MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&grp->P, &grp->P, 1));
MBEDTLS_MPI_CHK(mbedtls_mpi_shift_l(&grp->P, 224));
MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&grp->P, &grp->P, 1));
grp->pbits = mbedtls_mpi_bitlen(&grp->P); grp->pbits = mbedtls_mpi_bitlen(&grp->P);
/* Y intentionally not set, since we use x/z coordinates. /* Y intentionally not set, since we use x/z coordinates.
@ -4715,17 +4725,12 @@ static int ecp_use_curve448(mbedtls_ecp_group *grp)
MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&grp->G.Z, 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&grp->G.Z, 1));
mbedtls_mpi_free(&grp->G.Y); mbedtls_mpi_free(&grp->G.Y);
/* N = 2^446 - 13818066809895115352007386748515426880336692474882178609894547503885 */ ecp_mpi_load(&grp->N, curve448_n, sizeof(curve448_n));
MBEDTLS_MPI_CHK(mbedtls_mpi_set_bit(&grp->N, 446, 1));
MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&Ns,
curve448_part_of_n, sizeof(curve448_part_of_n)));
MBEDTLS_MPI_CHK(mbedtls_mpi_sub_mpi(&grp->N, &grp->N, &Ns));
/* Actually, the required msb for private keys */ /* Actually, the required msb for private keys */
grp->nbits = 447; grp->nbits = 447;
cleanup: cleanup:
mbedtls_mpi_free(&Ns);
if (ret != 0) { if (ret != 0) {
mbedtls_ecp_group_free(grp); mbedtls_ecp_group_free(grp);
} }