* curve: add `EdwardsPoint::compress_batch` and `::random`
We've had various requests to implement batch point compression for
`EdwardsPoint`, e.g. #705.
We can leverage `FieldElement::batch_invert` to implement it, which
results in a fairly significant speedup.
The name `EdwardsPoint::compress_batch` has been chosen to match
`RistrettoPoint::double_and_compress_batch`.
For benchmarking, randomized `EdwardsPoint`s have been used. To obtain
these, an inherent `EdwardsPoint::random` has been extracted from the
existing `Group::random` implementation, which uses rejection sampling.
`Group::random` has been updated to call the inherent
`EdwardsPoint::random`. This avoids a `group` dependency just to run the
batch compression benchmarks.
The following benchmark results have been obtained:
edwards benches/EdwardsPoint compression
time: [3.5029 µs 3.5098 µs 3.5171 µs]
edwards benches/Batch EdwardsPoint compression/1
time: [3.6698 µs 3.6758 µs 3.6817 µs]
edwards benches/Batch EdwardsPoint compression/2
time: [3.8410 µs 3.8461 µs 3.8516 µs]
edwards benches/Batch EdwardsPoint compression/4
time: [4.1534 µs 4.1961 µs 4.2558 µs]
edwards benches/Batch EdwardsPoint compression/8
time: [4.8466 µs 4.8533 µs 4.8600 µs]
edwards benches/Batch EdwardsPoint compression/16
time: [6.1216 µs 6.1315 µs 6.1410 µs]
As you can see, it affords a fairly significant speedup, batch
compressing 16 points in less time than the standard point compression
algorithm would take to compress 2 in a row.
* Mark constants::BASEPOINT_ORDER_PRIVATE deprecated from pub API
* Move all BASEPOINT_ORDER use private internally
Co-authored-by: Tony Arcieri <bascule@gmail.com>
* Fix CHANGELOG for 4.1.1
---------
Co-authored-by: Tony Arcieri <bascule@gmail.com>
Adds a lints section to the top of lib.rs with the following:
#![warn(
clippy::unwrap_used,
missing_docs,
rust_2018_idioms,
unused_lifetimes,
unused_qualifications
)]
`warn` is used instead of `deny` to prevent the lints from firing during
local development, however we already configure `-D warnings` in CI so
if any lint fails on checked-in code, it will cause a CI failure.
This commit also fixes or explicitly allows any current violations of
these lints. The main ones were:
- `clippy::unwrap_used`: replaces usages of `unwrap` with `expect`
- `rust_2018_idioms`: no implicit lifetimes, which were present on
usages of `core::fmt::Formatter`
