The first round of carry reduction can not generate a carry thus the
secound round is not needed. The comments illustrating when the
carry is 1. The reduction is simmetric so the case when the carry is
-1 is similar.
The illustration is trying to calculate the input value starting with
setting the carry to 1 before the second round of the carry reduction.
It calculates backwords and tries to determine the value range of
each word. It ends up with a contradiction that A10 must have the
value of 0 and UINT32_MAX.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
This patch introduces the following changes:
* Documentation for `mbedtls_ecp_modulus_setup()`
moved to `ecp_invasive.h`.
* Added invalid modulus selector `MBEDTLS_ECP_MOD_NONE`.
* Adjusted negative tests to use invalid selectors.
* Reworded documentation.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch introduces a new static method, responsible
for automatically initialising an modulus structure,
based on the curve id and a modulus type selector.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
Apply the usual parameter name and align the local variables and
comments. This naming diverges from the standard notation, but this is
beneficial as our variable meanings diverge as well and the difference
can help avoiding confusion.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
It is not necessary to save the middle limb upfront as overwriting it is
the desired result: in the first step we are reducing modulo
2^{512+biL}.
Arguably, the original flow is more intuitive and easier to see the idea
behind it.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
The prototype calculated with wrong limb size and not taken into account
the overflow in the shared limb.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
This patch adjusts the logic, so that the method is included,
when the following components are enabled:
* MBEDTLS_ECP_DP_CURVE448_ENABLED
* MBEDTLS_ECP_DP_CURVE25519_ENABLED
* ECP_LOAD_GROUP
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
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 patch adds two embedded constants used by `ecp_use_curve25519()`.
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>
