feat: removing nullifier from private FPC

[benesjan]

Leila recently implemented injection of nonces to public note hashes (relevant PR) and with that it's no longer necessary to prevent collisions of notes in the private refunds. These collisions were prevented until now by emitting randomness as a nullifier.

Context: Given that note hashes used to not be noncified it could happen that a user would emit the same note hash twice and effectively losing one of the notes (since it could not be nullified). To prevent this we used to emit user randomness (which is part of the note hash preimage).

Here is the original discussion.

[benesjan]

• feat: removing nullifier from private FPC #7765 👈
• feat: typing unfinalized partial notes #7742 : 1 other dependent PR (#7767 )
• master

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Benchmark results

Metrics with a significant change:

• protocol_circuit_simulation_time_in_ms (private-kernel-tail-to-public): 5,131 (+94%)
• avm_simulation_time_ms (Token:transfer_public): 34.6 (+33%)
• avm_simulation_time_ms (Token:_increase_public_balance): 111 (+45%)
• protocol_circuit_proving_time_in_ms (base-parity): 1,720 (+59%)

Detailed results

All benchmarks are run on txs on the Benchmarking contract on the repository. Each tx consists of a batch call to create_note and increment_balance, which guarantees that each tx has a private call, a nested private call, a public call, and a nested public call, as well as an emitted private note, an unencrypted log, and public storage read and write.

This benchmark source data is available in JSON format on S3 here.

Proof generation

Each column represents the number of threads used in proof generation.

Metric	1 threads	4 threads	16 threads	32 threads	64 threads
proof_construction_time_sha256_ms	5,725	1,541	705	744 (-1%)	766
proof_construction_time_sha256_30_ms	11,733	3,150	1,408	1,450 (+1%)	1,468
proof_construction_time_sha256_100_ms	43,857	12,394 (-1%)	5,675	5,576	5,507
proof_construction_time_poseidon_hash_ms	78.0	34.0	34.0 (-23%)	59.0 (-9%)	88.0 (-3%)
proof_construction_time_poseidon_hash_30_ms	1,519	415	200	230 (+2%)	267
proof_construction_time_poseidon_hash_100_ms	5,610	1,517	674	735 (+3%)	754 (+1%)

L2 block published to L1

Each column represents the number of txs on an L2 block published to L1.

Metric	4 txs	8 txs	16 txs
l1_rollup_calldata_size_in_bytes	740	740	740
l1_rollup_calldata_gas	6,716	6,716	6,704
l1_rollup_execution_gas	611,983	612,134	612,273
l2_block_processing_time_in_ms	247 (-11%)	429 (-5%)	824 (+3%)
l2_block_building_time_in_ms	9,401 (-1%)	18,455 (-4%)	36,593
l2_block_rollup_simulation_time_in_ms	9,401 (-1%)	18,455 (-4%)	36,593
l2_block_public_tx_process_time_in_ms	7,820 (-1%)	16,683 (-4%)	34,761

L2 chain processing

Each column represents the number of blocks on the L2 chain where each block has 8 txs.

Metric	3 blocks	5 blocks
node_history_sync_time_in_ms	2,684 (-1%)	3,479 (-7%)
node_database_size_in_bytes	12,681,296	16,904,272
pxe_database_size_in_bytes	16,254	26,813

Circuits stats

Stats on running time and I/O sizes collected for every kernel circuit run across all benchmarks.

Circuit	simulation_time_in_ms	witness_generation_time_in_ms	input_size_in_bytes	output_size_in_bytes	proving_time_in_ms	proof_size_in_bytes	num_public_inputs	size_in_gates
private-kernel-init	97.6 (+4%)	445 (+9%)	21,846	44,858	N/A	N/A	N/A	N/A
private-kernel-inner	174 (+4%)	749 (+4%)	72,545	45,005	N/A	N/A	N/A	N/A
private-kernel-tail	688 (+1%)	983 (+15%)	53,523	49,801	N/A	N/A	N/A	N/A
base-parity	6.02 (+2%)	599 (+4%)	160	96.0	⚠️ 1,720 (+59%)	13,188	19.0	65,536
root-parity	112 (+1%)	112 (+1%)	69,084	96.0	28,141 (+1%)	13,188	19.0	4,194,304
base-rollup	2,947 (-2%)	5,470 (-1%)	182,288	664	86,373	14,020	45.0	16,777,216
root-rollup	98.8 (+1%)	98.8	54,525	716	25,296 (-1%)	13,988	44.0	4,194,304
public-kernel-setup	91.3 (+1%)	2,739 (+1%)	102,617	69,814	15,402	127,172	3,581	2,097,152
public-kernel-app-logic	105 (-1%)	4,150	102,617	69,814	9,038 (-2%)	127,172	3,581	1,048,576
public-kernel-tail	582 (-3%)	29,374 (+2%)	402,342	10,878	93,332 (+1%)	26,436	433	16,777,216
private-kernel-reset-tiny	198 (+2%)	873	68,621	44,750	N/A	N/A	N/A	N/A
private-kernel-tail-to-public	⚠️ 5,131 (+94%)	1,636 (+2%)	977,330	1,697	N/A	N/A	N/A	N/A
public-kernel-teardown	97.6 (+13%)	4,190	102,617	69,814	16,462 (+1%)	127,172	3,581	2,097,152
merge-rollup	60.8 (+2%)	N/A	35,742	664	N/A	N/A	N/A	N/A
undefined	N/A	N/A	N/A	N/A	148,410	N/A	N/A	N/A

Stats on running time collected for app circuits

Function	input_size_in_bytes	output_size_in_bytes	witness_generation_time_in_ms	proof_size_in_bytes	proving_time_in_ms
ContractClassRegisterer:register	1,344	11,731	339	N/A	N/A
ContractInstanceDeployer:deploy	1,408	11,731	18.3 (+1%)	N/A	N/A
MultiCallEntrypoint:entrypoint	1,920	11,731	475	N/A	N/A
GasToken:deploy	1,376	11,731	388 (+1%)	N/A	N/A
SchnorrAccount:constructor	1,312	11,731	177	N/A	N/A
SchnorrAccount:entrypoint	2,304	11,731	567	N/A	N/A
Token:privately_mint_private_note	1,280	11,731	227 (+1%)	N/A	N/A
FPC:fee_entrypoint_public	1,344	11,731	31.4 (-6%)	N/A	N/A
Token:transfer	1,312	11,731	811	N/A	N/A
AuthRegistry:set_authorized (avm)	18,491	N/A	N/A	147,456	2,603 (-3%)
FPC:prepare_fee (avm)	22,958	N/A	N/A	147,520	3,216 (-6%)
Token:transfer_public (avm)	61,614	N/A	N/A	147,520	17,178 (-4%)
AuthRegistry:consume (avm)	41,719	N/A	N/A	147,488	7,753
FPC:pay_refund (avm)	26,227	N/A	N/A	147,488	7,515 (+2%)
Benchmarking:create_note	1,344	11,731	169 (-1%)	N/A	N/A
SchnorrAccount:verify_private_authwit	1,280	11,731	27.6 (+1%)	N/A	N/A
Token:unshield	1,376	11,731	759 (+1%)	N/A	N/A
FPC:fee_entrypoint_private	1,376	11,731	998 (+1%)	N/A	N/A

AVM Simulation

Time to simulate various public functions in the AVM.

Function	time_ms	bytecode_size_in_bytes
GasToken:_increase_public_balance	93.1 (+1%)	8,139
GasToken:set_portal	10.0 (-5%)	2,362
Token:constructor	119 (-2%)	31,107
FPC:constructor	92.8 (-1%)	24,011
GasToken:mint_public	78.8 (+1%)	6,150
Token:mint_public	90.5 (+7%)	11,720
Token:assert_minter_and_mint	81.2 (-15%)	8,028
AuthRegistry:set_authorized	9.76 (+27%)	4,537
FPC:prepare_fee	286	8,812
Token:transfer_public	⚠️ 34.6 (+33%)	47,374
FPC:pay_refund	63.8 (+4%)	12,114
Benchmarking:increment_balance	986 (+1%)	7,450
Token:_increase_public_balance	⚠️ 111 (+45%)	8,960
FPC:pay_refund_with_shielded_rebate	81.3 (+16%)	12,663

Public DB Access

Time to access various public DBs.

Function	time_ms
get-nullifier-index	0.149 (-3%)

Tree insertion stats

The duration to insert a fixed batch of leaves into each tree type.

Metric	1 leaves	16 leaves	64 leaves	128 leaves	256 leaves	512 leaves	1024 leaves
batch_insert_into_append_only_tree_16_depth_ms	2.15	4.02 (+3%)	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_count	16.8	31.7	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_ms	0.112	0.114 (+4%)	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_32_depth_ms	N/A	N/A	11.3 (+1%)	17.8 (-1%)	30.7 (-4%)	58.4 (-2%)	118 (+4%)
batch_insert_into_append_only_tree_32_depth_hash_count	N/A	N/A	95.9	159	287	543	1,055
batch_insert_into_append_only_tree_32_depth_hash_ms	N/A	N/A	0.108 (+1%)	0.104 (-1%)	0.0999 (-4%)	0.101 (-2%)	0.106 (+4%)
batch_insert_into_indexed_tree_20_depth_ms	N/A	N/A	14.3	26.3 (+3%)	43.4 (-1%)	81.2 (-2%)	173 (+7%)
batch_insert_into_indexed_tree_20_depth_hash_count	N/A	N/A	109	207	355	691	1,363
batch_insert_into_indexed_tree_20_depth_hash_ms	N/A	N/A	0.109	0.107 (+4%)	0.105 (-1%)	0.101 (-1%)	0.107 (+4%)
batch_insert_into_indexed_tree_40_depth_ms	N/A	N/A	16.5	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_count	N/A	N/A	133	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_ms	N/A	N/A	0.106	N/A	N/A	N/A	N/A

Miscellaneous

Transaction sizes based on how many contract classes are registered in the tx.

Metric	0 registered classes	1 registered classes
tx_size_in_bytes	62,729	664,455

Transaction size based on fee payment method

| Metric | |
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