fix(ole-core): use original ROT choice bits in OLE receiver#377
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fix(ole-core): use original ROT choice bits in OLE receiver#377heeckhau wants to merge 1 commit into
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For prime fields where 2^k > p (e.g. P256), converting ROT choice bits
to a field element via `from_lsb0_iter` and then back via `iter_lsb0`
can produce different bits due to modular reduction. This caused the
OLE additive share computation to use bits inconsistent with the ROT
messages, breaking correctness (~2^{-32} probability per OLE for P256).
Additionally, ark-ff panics when `from_lsb0_iter` receives a value >= p,
making this a potential crash in production.
The fix computes both the additive and multiplicative shares directly
from the original choice bits using field arithmetic, which naturally
reduces without altering the bit representation.
Closes #343
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Summary
2^k > p(e.g. P256), the OLE receiver converted ROT choice bits to a field element viafrom_lsb0_iterthen back viaiter_lsb0. This round-trip can alter bits due to modular reduction, causing the additive share computation to use bits inconsistent with the ROT messages.From<BigInt>panics for values >= p, making this a potential crash (~2^{-32} probability per OLE for P256).itybitydependency frommpz-ole-core.Closes #343
Test plan
test_ole_p256_choices_exceed_primewith all-ones bits (value >= p) — passes with fix, fails withoutmpz-ole-coretests pass (11/11)mpz-ole,mpz-share-conversion-core,mpz-share-conversiontlsntest suite passes with patched mpz (via[patch]in Cargo.toml)🤖 Generated with Claude Code