Branch free witness generation - #97
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This was referenced Aug 4, 2026
burdges
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Aug 10, 2026
| .iter() | ||
| .map(|&b| if b { F::one() } else { F::zero() }) | ||
| .collect(); | ||
| let bits_as_field_elements = bits.iter().map(|&bit| bit_to_field(bit)).collect(); |
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I'd probably have passed an iterator here, but whatever.
burdges
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Aug 10, 2026
| //! branches and memory indexing out of witness generation. They are defense | ||
| //! in depth, not a complete side-channel countermeasure: later pipeline | ||
| //! stages (in particular the polynomial commitment MSMs) still process the | ||
| //! witness in variable time. |
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Why not use https://github.com/dalek-cryptography/subtle here?
Arkworks doesn't have constant time below us, but nothing wrong in having our stuff be constant time, and hoping their improves. Also, one could write arkworks curve wrappers over curves that claim constant time, although whether this claims hold is another matter.
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Yeah subtle introduction is a nice follow-up. Perhaps I'll open a PR to introduce it.
But let's first ship these crates as downstream we need them for production asap
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I'm fine to merge this. It's a bit over the time imho, but whatever. |
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Remove secret-dependent branches and memory indexing from witness generation
Audit issue reference: https://github.com/paritytech/srlabs_findings/issues/709