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Blob accumulation is underconstrained #15310

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Blob accumulation is underconstrained#15310

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@TomAFrench
TomAFrench
opened on Jun 26, 2025

See related issue: noir-lang/noir_bigcurve#77

Blob batching relies on this function in order to add points into the accumulator:

aztec-packages/noir-projects/noir-protocol-circuits/crates/blob/src/blob_batching_public_inputs.nr

Lines 231 to 233 in 7a716b3

c_acc: self.c_acc.add(other.c_i.point.mul(BLS12_381Scalar::from_bignum(
self.gamma_pow_acc,
))),

Opening an issue here to flag that the protocol circuits are underconstrained and should be updated once the above issue is fixed.

cc @MirandaWood

Activity

  1. MirandaWood commented on Jun 27, 2025

    @MirandaWood
    MirandaWood
    on Jun 27, 2025
    Contributor

    Thank you for flagging this! I didn't realise from_bignum was underconstrained - if we want a quick fix in a-p, could we instead have an unconstrained helper to return the scalar and use into_bignum then check equality? (I don't see anything suggesting into_bignum isn't constrained).
    @iAmMichaelConnor for info

  2. MirandaWood
    added a parent issue on Jun 27, 2025
  3. TomAFrench
    closed this as completedon Jul 11, 2025
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