curve: add EdwardsPoint::compress_batch and inherent ::random
#759
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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.
This was referenced May 26, 2025
tarcieri
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May 26, 2025
tarcieri
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May 26, 2025
tarcieri
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May 26, 2025
tarcieri
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May 26, 2025
rozbb
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rozbb
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We've had various requests to implement batch point compression for
EdwardsPoint, e.g. #705.We can leverage
FieldElement::batch_invertto implement it, which results in a fairly significant speedup.The name
EdwardsPoint::compress_batchhas been chosen to matchRistrettoPoint::double_and_compress_batch.For benchmarking, randomized
EdwardsPoints have been used. To obtain these, an inherentEdwardsPoint::randomhas been extracted from the existingGroup::randomimplementation, which uses rejection sampling.Group::randomhas been updated to call the inherentEdwardsPoint::random. This avoids agroupdependency just to run the batch compression benchmarks.The following benchmark results have been obtained:
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.