From 80c4ae893cc0fb6beb88300ec1716d245d195fe4 Mon Sep 17 00:00:00 2001 From: Minos Galanakis Date: Tue, 27 Jun 2023 16:34:59 +0100 Subject: [PATCH] bignum_common.py: Added `bits_to_limbs` method. This patch introduces a rounding-error-resiliant method to calculate bits_to_limbs, and is updating `SECP224R1` and `SECP224K1` to use it. Signed-off-by: Minos Galanakis --- scripts/mbedtls_dev/bignum_common.py | 10 ++++++++-- scripts/mbedtls_dev/ecp.py | 6 ++++-- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/scripts/mbedtls_dev/bignum_common.py b/scripts/mbedtls_dev/bignum_common.py index 51b25a3715..3bef16db68 100644 --- a/scripts/mbedtls_dev/bignum_common.py +++ b/scripts/mbedtls_dev/bignum_common.py @@ -19,6 +19,7 @@ import enum from typing import Iterator, List, Tuple, TypeVar, Any from copy import deepcopy from itertools import chain +from math import ceil from . import test_case from . import test_data_generation @@ -76,9 +77,14 @@ def combination_pairs(values: List[T]) -> List[Tuple[T, T]]: """Return all pair combinations from input values.""" return [(x, y) for x in values for y in values] +def bits_to_limbs(bits: int, bits_in_limb: int) -> int: + """ Return the appropriate ammount of limbs needed to store + a number contained in input bits""" + return ceil(bits / bits_in_limb) + def hex_digits_for_limb(limbs: int, bits_in_limb: int) -> int: - """ Retrun the hex digits need for a number of limbs. """ - return 2 * (limbs * bits_in_limb // 8) + """ Return the hex digits need for a number of limbs. """ + return 2 * ((limbs * bits_in_limb) // 8) def hex_digits_max_int(val: str, bits_in_limb: int) -> int: """ Return the first number exceeding maximum the limb space diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py index 8a3ab281f0..ed79a073c4 100644 --- a/scripts/mbedtls_dev/ecp.py +++ b/scripts/mbedtls_dev/ecp.py @@ -165,7 +165,8 @@ class EcpP224R1Raw(bignum_common.ModOperationCommon, @property def arg_a(self) -> str: - hex_digits = bignum_common.hex_digits_for_limb(448 // self.bits_in_limb, self.bits_in_limb) + limbs = 2 * bignum_common.bits_to_limbs(224, self.bits_in_limb) + hex_digits = bignum_common.hex_digits_for_limb(limbs, self.bits_in_limb) return super().format_arg('{:x}'.format(self.int_a)).zfill(hex_digits) def result(self) -> List[str]: @@ -624,7 +625,8 @@ class EcpP224K1Raw(bignum_common.ModOperationCommon, @property def arg_a(self) -> str: - hex_digits = bignum_common.hex_digits_for_limb(448 // self.bits_in_limb, self.bits_in_limb) + limbs = 2 * bignum_common.bits_to_limbs(224, self.bits_in_limb) + hex_digits = bignum_common.hex_digits_for_limb(limbs, self.bits_in_limb) return super().format_arg('{:x}'.format(self.int_a)).zfill(hex_digits) def result(self) -> List[str]: