ecc: constrain incomplete-mul base to the actual base point#2
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The variable-base scalar-multiplication gadget assigned the base point's coordinates into the incomplete-addition loop with `assign_advice`, which introduces an unconstrained witness. The `q_mul_2` gate only forces the per-row `x_p`/`y_p` values to equal each other, never to equal the actual `base`. A malicious prover could therefore set the loop's base to any point P and compute [scalar]·P instead of [scalar]·base, breaking the soundness of variable-base scalar mul (e.g. the `pk_d == [ivk] g_d` recipient-integrity check, enabling note-ownership forgery / multiple nullifiers per note). Copy the base coordinates in on the first row so they are constrained to the real base; the existing `q_mul_2` equality gate propagates the binding across the remaining rows.
zeapoz
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Jun 10, 2026
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Change looks good to me, but let's fix the CI checks too
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Addresses the Orchard Security Bug:
https://drive.google.com/file/d/1SVK41y-ip3Vw9eB69E9QRy-Qn3idTOwV/view