refactor: fpc optimization, cleanup + docs #10555

benesjan · 2024-12-09T21:49:15Z

FPC code docs, overall cleanup and refactor, improved naming, ContractFunctionInteraction fix.

Note 1: Based on Nico's feedback the fee is paid in public and not in private (only the refund is paid in private as we need to conceal the identity of the user --> identity of the FPC is public so no need to waste resources on the private note).

Note 2: there is no longer a fee_recipient passed to the setup_refund function as it's no longer required --> before it was required because we needed someone to receive the fee note and the FPC could not receive notes. With the change to public we just send the fee directly to FPC.

benesjan · 2024-12-09T21:49:32Z

refactor: fpc optimization, cleanup + docs #10555 👈 (View in Graphite)
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github-actions · 2024-12-11T01:34:09Z

Changes to public function bytecode sizes

Generated at commit: 08c6b6647bb7f2b024023f319e54711f3d28bf45, compared to commit: 970ad77966a17fd5c8071a7c3c3a405f83630c5d

🧾 Summary (100% most significant diffs)

Program	Bytecode size in bytes (+/-)	%
Token::complete_refund	+1,438 ❌	+26.10%
FPC::public_dispatch	+404 ❌	+5.39%
Token::public_dispatch	+212 ❌	+0.65%

Full diff report 👇

Program	Bytecode size in bytes (+/-)	%
Token::complete_refund	6,948 (+1,438)	+26.10%
FPC::public_dispatch	7,905 (+404)	+5.39%
Token::public_dispatch	32,739 (+212)	+0.65%

noir-projects/noir-contracts/contracts/fpc_contract/src/config.nr

noir-projects/noir-contracts/contracts/fpc_contract/src/lib.nr

benesjan · 2024-12-11T02:16:03Z

noir-projects/noir-contracts/contracts/fpc_contract/src/main.nr

    #[public]
    #[internal]
-    fn prepare_fee(from: AztecAddress, amount: Field, asset: AztecAddress, nonce: Field) {


Nuked this function as it was superfluous --> we could just enqueue the call to the token directly from the private function (which saves 1 kernel iteration).

benesjan · 2024-12-11T02:16:34Z

noir-projects/noir-contracts/contracts/fpc_contract/src/main.nr

    #[private]
-    fn fee_entrypoint_public(amount: Field, asset: AztecAddress, nonce: Field) {
-        FPC::at(context.this_address())


Nuked the prepare_fee function as it was superfluous --> we could just enqueue the call to the token directly from the private function (which saves 1 kernel iteration).

benesjan · 2024-12-11T02:17:05Z

noir-projects/noir-contracts/contracts/fpc_contract/src/main.nr

-            &mut context,
-        );
+    #[view]
+    fn get_accepted_asset() -> AztecAddress {


Exposed this so that we can load this info directly from contract instead of having to pass that value in our TS API.

benesjan · 2024-12-11T02:17:48Z

noir-projects/noir-contracts/contracts/token_contract/src/main.nr

@@ -615,9 +615,9 @@ contract Token {

    /// We need to use different randomness for the user and for the fee payer notes because if the randomness values


Unified the naming in this contract with FPC.

benesjan · 2024-12-11T02:18:36Z

yarn-project/aztec.js/src/fee/private_fee_payment_method.ts

@@ -42,8 +41,40 @@ export class PrivateFeePaymentMethod implements FeePaymentMethod {
   * The asset used to pay the fee.
   * @returns The asset used to pay the fee.
   */
-  getAsset() {
-    return this.asset;
+  getAsset(): Promise<AztecAddress> {


Now obtaining the value directly from the contract --> this declutters the API.

benesjan · 2024-12-11T17:46:13Z

yarn-project/aztec.js/src/contract/contract_function_interaction.ts

-    // since we're interested in the first set of values AFTER the account entrypoint
-    // For public functions we retrieve the first values directly from the public output.
-    const rawReturnValues =
-      this.functionDao.functionType == FunctionType.PRIVATE


This assumed that we always simulate via an account contract and if we did not it would fail with undefined. Since I did exactly that in this PR I've stumbled upon this. Note that there is a new issue that needs to be tackled.

nventuro · 2024-12-14T16:00:15Z

noir-projects/noir-contracts/contracts/fpc_contract/src/main.nr

+    /// 1. `setup_refund` function subtracts the `max_fee` from user's balance of AA, prepares partial notes
+    /// for the `private_fee_recipient` (to obtain the payment in AA for the fee) and for the msg_sender (for refund
+    /// note of the AA) and sets a public teardown function (in which the partial notes will be finalized),
+    /// 2. then the private and public functions of a tx get executed,


Why does private_fee_recipient need to receive the payment privately? The amount is public, and the address is public. Can't we just send them public balance? That'd be much cheaper since there are no logs etc., and also less gates.

Makes total sense. Will do the change 👍

Maybe not as part of this PR, but I do think we need an example for how someone can pay a fee privately with the following kept private:

The user

The FPC contract address

The asset used to pay the fee.

If there are to be many FPCs on Aztec, then this information will drastically reduce Aztec's global privacy set.

Ideally we'd have an example of a way to pay fees without leaking any of this info.

Created an issue for this.

If there are to be many FPCs on Aztec, then this information will drastically reduce Aztec's global privacy set.

As we discussed in a scrum, this could be alleviated by us integrating the FPC with the token contract and allowing only for a few of those (e.g. 2 stablecoins and ETH).

This reverts commit c29b2ca.

This reverts commit 0a7985b.

Co-authored-by: Michael Connor <mike@aztecprotocol.com>

benesjan force-pushed the 12-09-refactor_fpc_cleanup_docs branch 4 times, most recently from 35a2868 to bc6c54b Compare December 11, 2024 00:59

benesjan added the e2e-all CI: Enables this CI job. label Dec 11, 2024

benesjan marked this pull request as ready for review December 11, 2024 01:18

benesjan marked this pull request as draft December 11, 2024 01:18

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benesjan commented Dec 11, 2024

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benesjan requested review from nventuro and Thunkar December 11, 2024 13:26

benesjan force-pushed the 12-09-refactor_fpc_cleanup_docs branch from 7338f52 to ae343c7 Compare December 11, 2024 13:29

benesjan marked this pull request as draft December 11, 2024 16:00

benesjan force-pushed the 12-09-refactor_fpc_cleanup_docs branch from ae343c7 to ceabdbb Compare December 11, 2024 16:01

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benesjan commented Dec 11, 2024

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benesjan requested a review from iAmMichaelConnor December 12, 2024 14:09

nventuro reviewed Dec 14, 2024

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benesjan marked this pull request as draft December 16, 2024 16:27

benesjan force-pushed the 12-09-refactor_fpc_cleanup_docs branch 2 times, most recently from 6949ccf to bd10e66 Compare December 16, 2024 18:28

benesjan marked this pull request as ready for review December 16, 2024 18:35

benesjan and others added 25 commits December 17, 2024 19:09

last touches to FPC

cc3cddb

WIP

870a9ff

WIP

4ab7e34

WIP

ce9f06c

WIP

c392e16

fetching accepted asset from FPC

bda3dfc

test fix

3fa0815

error msg fix

4fcfb4f

Revert "fetching accepted asset from FPC"

6299e36

This reverts commit c29b2ca.

wip

b94f5e4

Reapply "fetching accepted asset from FPC"

f07ace8

This reverts commit 0a7985b.

fix

0d7052b

comment fix

8db573c

unrelated clarifying comment

6476094

paying fee in public

7bca358

fix?

b341927

WIP

93cbc74

fmt

bbd059c

nuking unused feeRecipient param

e184ff6

fix

2133e71

comment fix

2039767

Update noir-projects/noir-contracts/contracts/fpc_contract/src/main.nr

e3bd310

Co-authored-by: Michael Connor <mike@aztecprotocol.com>

flamegraph.sh fix

7718d51

comment improvements

48911fd

comment fix

03946d4

benesjan force-pushed the 12-09-refactor_fpc_cleanup_docs branch from 41c3df4 to 03946d4 Compare December 17, 2024 19:14

benesjan added 2 commits December 17, 2024 15:20

Merge branch 'master' into 12-09-refactor_fpc_cleanup_docs

957c3a0

Merge branch 'master' into 12-09-refactor_fpc_cleanup_docs

b7c0c92

benesjan merged commit e23fd0d into master Dec 18, 2024
72 checks passed

benesjan deleted the 12-09-refactor_fpc_cleanup_docs branch December 18, 2024 15:56

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refactor: fpc optimization, cleanup + docs #10555

refactor: fpc optimization, cleanup + docs #10555

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benesjan Dec 17, 2024

		@@ -615,9 +615,9 @@ contract Token {

		/// We need to use different randomness for the user and for the fee payer notes because if the randomness values

refactor: fpc optimization, cleanup + docs #10555

refactor: fpc optimization, cleanup + docs #10555

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benesjan commented Dec 9, 2024 • edited Loading

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github-actions bot commented Dec 11, 2024 • edited Loading

Changes to public function bytecode sizes

🧾 Summary (100% most significant diffs)

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benesjan commented Dec 9, 2024 •

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