Add BoxedUint::inv_mod
#341
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Support for computing modular inverses, proptested against the
implementation in `num-bigint-dig`, which this commit also switches to
(`num-bigint` doesn't provide an implementation we can test against).
Uses the same method as `Uint::inv_mod`, namely an algorithm equivalent
to GMP's `mpn_sec_invert`, with code largely duplicated from the `Uint`
version.
Notably this version is variable time with respect to the modulus,
which might be avoidable with alternative implementations, such as
Bernstein-Yang.
It would also be nice to deduplicate the implementation, though reuse
between `const fn` use cases and heap-backed use cases is difficult.
This additionally adds the following prerequisites:
- `BoxedUint::{conditional_assign, conditional_swap, is_one}
- `BoxedUint::conditional_wrapping_*` (private)
- `BoxedUint::{trailing_zeros, wrapping_mul, neg}`
- `BoxedUint::{shl, shr}`
tarcieri
force-pushed
the
boxed-uint/inv-mod
branch
from
2cce69c to
fc50900
Compare
Merged
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Support for computing modular inverses, proptested against the implementation in
num-bigint-dig, which this commit also switches to (num-bigintdoesn't provide an implementation we can test against).Uses the same method as
Uint::inv_mod, namely an algorithm equivalent to GMP'smpn_sec_invert, with code largely duplicated from theUintversion.Notably this version is variable time with respect to the modulus, which might be avoidable with alternative implementations, such as Bernstein-Yang.
It would also be nice to deduplicate the implementation, though reuse between
const fnuse cases and heap-backed use cases is difficult.This additionally adds the following prerequisites:
BoxedUint::conditional_wrapping_*(private)BoxedUint::{trailing_zeros, wrapping_mul, neg}BoxedUint::{shl, shr}