chore(docs): common patterns and anti patterns in aztec.nr

[rahul-kothari]

Add a list of common patterns and anti patterns when writing Aztec.nr

For a quick glance - just look at all the headings in common_patterns/main.md and lmk if there is any I have missed

[spalladino]

Suggested change

	### Approving another user/contract to call a function on your behalf
	### Approving another user/contract to execute an action on your behalf

[spalladino]

This one feels off, since private -> public flows can also happen across different contracts, and internal doesn't make sense in those cases. Maybe we need to narrow down the scenario? For instance, following the lead from the previous one, we could do: "Writing public storage from private: If you want to update public state from private, you can call a public function from private, just make sure you mark public as internal".

[spalladino]

So try to not pass the address

What address?

[spalladino]

I'd add the pattern of shared private note that came up from the work with Wonderland: if you have private state that needs to be handled by more than a single user (but no more than a handful), you can add the note commitment to the private data tree, and then encrypt the note once for each of the users that need to see it. And if any of those users should be able to consume the note, you can generate a random nullifier on creation and store it in the encrypted note, instead of relying on the user secret.

[iAmMichaelConnor]

Should we warn that this leaks information about the private function that was executed (and the data which has been read)? This almost seems like an anti-pattern for privacy?

[iAmMichaelConnor]

These sentences aren't clear to me.

[benesjan]

What if the contract doesn't emit such logs?

This is a bit weird as it's up to the developer to set this.

Instead I would describe here that a dev might be inclined here to not emit the logs to save gas.

[benesjan]

I would not even mention this here since the function will be eventually removed and now it looks like this:

[benesjan]

I would not use the term replay attack here because this is not really a replay attack.

"A replay attack occurs when a cybercriminal eavesdrops on a secure network communication, intercepts it, and then fraudulently delays or resends it to misdirect the receiver into doing what the hacker wants. The added danger of replay attacks is that a hacker doesn't even need advanced skills to decrypt a message after capturing it from the network. The attack could be successful simply by resending the whole thing."

[AztecBot]

Benchmark results

No metrics with a significant change found.

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.

Values are compared against data from master at commit d94d88bf and shown if the difference exceeds 1%.

L2 block published to L1

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

Metric	8 txs	32 txs	128 txs
l1_rollup_calldata_size_in_bytes	45,444	179,588	716,132
l1_rollup_calldata_gas	222,900	868,064	3,449,612
l1_rollup_execution_gas	841,987	3,595,172	22,204,981
l2_block_processing_time_in_ms	2,052 (+1%)	7,782 (+1%)	30,701 (+1%)
note_successful_decrypting_time_in_ms	303	879 (-2%)	3,191 (-4%)
note_trial_decrypting_time_in_ms	7.49 (+22%)	89.6 (-17%)	142 (-1%)
l2_block_building_time_in_ms	20,671 (-1%)	81,850	327,335
l2_block_rollup_simulation_time_in_ms	11,998 (-1%)	47,476	189,458
l2_block_public_tx_process_time_in_ms	8,629	34,233	137,353

L2 chain processing

Each column represents the number of blocks on the L2 chain where each block has 16 txs.

Metric	5 blocks	10 blocks
node_history_sync_time_in_ms	21,876	42,760 (-1%)
note_history_successful_decrypting_time_in_ms	2,044	3,987 (-1%)
note_history_trial_decrypting_time_in_ms	125 (-1%)	222 (+10%)
node_database_size_in_bytes	1,630,302	1,096,704
pxe_database_size_in_bytes	29,748	59,307

Circuits stats

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

Circuit	circuit_simulation_time_in_ms	circuit_input_size_in_bytes	circuit_output_size_in_bytes
private-kernel-init	768	61,697	18,905
private-kernel-ordering	127	24,297	8,153
base-rollup	1,755	656,428	873
root-rollup	169	4,072	1,097
private-kernel-inner	791	81,568	18,905
public-kernel-private-input	569	41,519	18,905
public-kernel-non-first-iteration	408	41,561	18,905
merge-rollup	15.5	2,592	873

Miscellaneous

Transaction sizes based on how many contracts are deployed in the tx.

Metric	0 deployed contracts	1 deployed contracts
tx_size_in_bytes	8,787	27,547

[benesjan]

Once you'll update the link I'll approve it.

[benesjan]

This link should be updated.