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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BEGIN_COMMIT_OVERRIDE fix: skip heavy recursion tests in debug builds (#22446) fix: add clear error for unsatisfiable ACIR AssertZero opcode (#22417) feat: enforce accumulator_not_empty = 0 at ECCVM lagrange_first row (#22461) fix: skip heavy recursion tests in debug builds, keep one for assertion coverage (#22389) fix: external audit fixes for Pedersen (#22434) chore!: fix BASE off-by-one in create_small_range_constraint in theta step of keccak (#22404) fix: external audit fixes for Keccak (#22436) fix: external audit fixes for BLAKE (#22443) chore: misc hash gadget updates (#22452) END_COMMIT_OVERRIDE
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…22461) ## Summary Add `lagrange_first * transcript_accumulator_not_empty = 0` subrelation to `ECCVMTranscriptRelation`. This is a prerequisite for #22334 (masking at top of ECCVM circuit). The audit in #22442 identified that when `lagrange_first` moves to row k (away from the PCS-enforced zero row), `transcript_accumulator_not_empty` is the only shiftable column where a malicious prover can potentially set a non-zero value at the `lagrange_first` row without any existing relation catching it. Setting it to 1 disables `INFINITY_ACC_X/Y`, allowing arbitrary accumulator coordinates to be injected. ## Changes - New subrelation `ACCUMULATOR_NOT_EMPTY_INIT` in `ecc_transcript_relation.hpp` (degree 2) - Gate count updates (+174 gates from the new subrelation): - `ECCVM_RECURSIVE_VERIFIER_GATE_COUNT`: 224336 → 224510 - `CHONK_RECURSION_GATES`: 1491593 → 1491767 ## Test plan - [x] `eccvm_tests` — all 44 tests pass - [x] `stdlib_eccvm_verifier_tests` — `SingleRecursiveVerification` passes with updated gate count - [x] `dsl_tests` — `GateCountChonkRecursion` passes with updated gate count Co-authored-by: notnotraju <raju@aztec-labs.com>
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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