feat: enforce accumulator_not_empty = 0 at ECCVM lagrange_first row#22461
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notnotraju merged 1 commit intomerge-train/barretenbergfrom Apr 10, 2026
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…ipt relation In preparation for masking at the top of the ECCVM circuit (where lagrange_first moves to row k = NUM_DISABLED_ROWS_IN_SUMCHECK and shiftable column values at row k are no longer PCS-enforced to be zero), add ACCUMULATOR_NOT_EMPTY_INIT subrelation to ECCVMTranscriptRelation. Without this constraint, a malicious prover could set accumulator_not_empty = 1 at the lagrange_first row, disabling INFINITY_ACC_X/Y and injecting arbitrary accumulator coordinates undetected. Update recursive verifier gate counts (+174 gates from the new subrelation): - ECCVM_RECURSIVE_VERIFIER_GATE_COUNT: 224336 → 224510 - CHONK_RECURSION_GATES: 1491593 → 1491767
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amazing, thanks for identifying this
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Summary
Add
lagrange_first * transcript_accumulator_not_empty = 0subrelation toECCVMTranscriptRelation.This is a prerequisite for #22334 (masking at top of ECCVM circuit). The audit in #22442 identified that when
lagrange_firstmoves to row k (away from the PCS-enforced zero row),transcript_accumulator_not_emptyis the only shiftable column where a malicious prover can potentially set a non-zero value at thelagrange_firstrow without any existing relation catching it. Setting it to 1 disablesINFINITY_ACC_X/Y, allowing arbitrary accumulator coordinates to be injected.Changes
ACCUMULATOR_NOT_EMPTY_INITinecc_transcript_relation.hpp(degree 2)ECCVM_RECURSIVE_VERIFIER_GATE_COUNT: 224336 → 224510CHONK_RECURSION_GATES: 1491593 → 1491767Test plan
eccvm_tests— all 44 tests passstdlib_eccvm_verifier_tests—SingleRecursiveVerificationpasses with updated gate countdsl_tests—GateCountChonkRecursionpasses with updated gate count