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feat: enforce accumulator_not_empty = 0 at ECCVM lagrange_first row #22461

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Merged
notnotraju merged 1 commit into from
Apr 10, 2026
Merged

feat: enforce accumulator_not_empty = 0 at ECCVM lagrange_first row #22461

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4 changes: 2 additions & 2 deletions barretenberg/cpp/src/barretenberg/dsl/acir_format/gate_count_constants.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -113,7 +113,7 @@ constexpr std::tuple<size_t, size_t> HONK_RECURSION_CONSTANTS(
// ========================================

// Gate count for Chonk recursive verification (Ultra with RollupIO)
inline constexpr size_t CHONK_RECURSION_GATES = 1491593;
inline constexpr size_t CHONK_RECURSION_GATES = 1491767;

// ========================================
// Hypernova Recursion Constants
Expand Down Expand Up @@ -147,7 +147,7 @@ inline constexpr size_t HIDING_KERNEL_ULTRA_OPS = 127;
// ========================================

// Gate count for ECCVM recursive verifier (Ultra-arithmetized)
inline constexpr size_t ECCVM_RECURSIVE_VERIFIER_GATE_COUNT = 224336;
inline constexpr size_t ECCVM_RECURSIVE_VERIFIER_GATE_COUNT = 224510;

// ========================================
// Goblin AVM Recursive Verifier Constants
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6 changes: 4 additions & 2 deletions barretenberg/cpp/src/barretenberg/relations/ecc_vm/ecc_transcript_relation.hpp
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Expand Up @@ -99,11 +99,13 @@ template <typename FF_> class ECCVMTranscriptRelationImpl {
INFINITY_ACC_X = 29,
// Infinity flag consistency: acc_y = 0 when accumulator empty
INFINITY_ACC_Y = 30,
// Boundary: accumulator_not_empty must be 0 at lagrange_first row
ACCUMULATOR_NOT_EMPTY_INIT = 31,
NUM_SUBRELATIONS,
};

static constexpr std::array<size_t, 31> SUBRELATION_PARTIAL_LENGTHS{
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
static constexpr std::array<size_t, 32> SUBRELATION_PARTIAL_LENGTHS{
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
};
static_assert(NUM_SUBRELATIONS == SUBRELATION_PARTIAL_LENGTHS.size());

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9 changes: 9 additions & 0 deletions barretenberg/cpp/src/barretenberg/relations/ecc_vm/ecc_transcript_relation_impl.hpp
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Expand Up @@ -566,5 +566,14 @@ void ECCVMTranscriptRelationImpl<FF>::accumulate(ContainerOverSubrelations& accu
is_accumulator_empty * transcript_accumulator_x * scaling_factor; // degree 2
std::get<INFINITY_ACC_Y>(accumulator) +=
is_accumulator_empty * transcript_accumulator_y * scaling_factor; // degree 2

/**
* @brief Enforce accumulator_not_empty = 0 at the lagrange_first row.
* Without this, a malicious prover can set accumulator_not_empty = 1 at the lagrange_first row,
* which disables INFINITY_ACC_X/Y above, allowing arbitrary accumulator coordinates to be injected
* without any relation catching it.
*/
std::get<ACCUMULATOR_NOT_EMPTY_INIT>(accumulator) +=
lagrange_first * View(in.transcript_accumulator_not_empty) * scaling_factor; // degree 2
}
} // namespace bb
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