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docs(yellow-paper): Update kernel with changes from contract deployme…
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…nt (#4432)

Updates private kernel inputs with changes from contract deployment.

These changes were implemented in #4337
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@spalladino @TomAFrench
spalladino authored and TomAFrench committed Feb 7, 2024
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30 changes: 9 additions & 21 deletions yellow-paper/docs/circuits/private-kernel-initial.md
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Expand Up @@ -22,8 +22,6 @@ For the _[function_data](#functiondata)_ in _[private_call](#privatecall).[call_

- It must be a private function:
- _`function_data.function_type == private`_
- It must not be an internal function:
- _`function_data.is_internal == false`_

#### Ensuring the function call is the first call.

Expand Down Expand Up @@ -65,23 +63,23 @@ With the following data provided from _[private_inputs](#private-inputs).[privat

This circuit validates the existence of the function in the contract through the following checks:

1. Verify that the _contract_address_ can be derived from the _contract_data_:
1. Verify that the _contract_address_ can be derived from the _public_keys_hash_, _salted_initialization_hash_, and a _contract_class_id.

Refer to the details [here](../contract-deployment/instances.md#address) for the process of computing the address for a contract instance.

2. Verify that the _contract_data.contract_class_id_ can be derived from the given _contract_class_data_:
2. Verify that _contract_class_id_ in the _contract_address_ preimage can be derived from the _contract_class_artifact_hash_, _contract_class_public_bytecode_commitment_, and a _private_functions_root_.

Refer to the details [here](../contract-deployment/classes.md#class-identifier) for the process of computing the _contract_class_id_.

3. Verify that _contract_class_data.private_functions_ includes the function being called:
3. Verify that _contract_class.private_functions_ includes the function being called:

1. Compute the hash of the verification key:
- _`vk_hash = hash(private_call.vk)`_
2. Compute the function leaf:
- _`hash(function_data.selector, vk_hash, private_call.bytecode_hash)`_
- _`hash(function_data.selector, vk_hash)`_
3. Perform a membership check on the function leaf, where:
- The index and sibling path are provided through _function_leaf_membership_witness_ within _[private_call](#privatecall)_.
- The root is _contract_class_data.private_functions_.
- The root is in the preimage of the _contract_class_id_ from the previous step.

#### Verifying the private function proof.

Expand Down Expand Up @@ -237,8 +235,10 @@ Data that holds details about the current private function call.
| _proof_ | _Proof_ | Proof of the private function circuit. |
| _vk_ | _VerificationKey_ | Verification key of the private function circuit. |
| _bytecode_hash_ | _field_ | Hash of the function bytecode. |
| _contract_data_ | _[ContractInstance](../contract-deployment/instances.md#structure)_ | Data of the contract instance being called. |
| _contract_class_data_ | _[ContractClassData](#contractclassdata)_ | Data of the contract class. |
| _salted_initialization_hash_ | _field_ | Part of the address preimage. |
| _public_keys_hash_ | _field_ | Part of the address preimage. |
| _contract_class_artifact_hash_ | _field_ | Part of the contract class identifier preimage. |
| _contract_class_public_bytecode_commitment_ | _field_ | Part of the contract class identifier preimage. |
| _function_leaf_membership_witness_ | _[MembershipWitness](#membershipwitness)_ | Membership witness for the function being called. |

## Public Inputs
Expand Down Expand Up @@ -277,18 +277,6 @@ Data that remains the same throughout the entire transaction.
| ------------------- | ---------------------------------- | --------------------------------------------------- |
| _function_selector_ | _u32_ | Selector of the function being called. |
| _function_type_ | private \| public \| unconstrained | Type of the function being called. |
| _is_internal_ | _bool_ | A flag indicating whether the function is internal. |

#### _ContractClassData_

| Field | Type | Description |
| ------------------------- | -------------- | ------------------------------------------------------------------ |
| _version_ | _u8_ | Version identifier. |
| _registerer_address_ | _AztecAddress_ | Address of the canonical contract used for registering this class. |
| _artifact_hash_ | _field_ | Hash of the contract artifact. |
| _private_functions_ | _field_ | Merkle root of the private function tree. |
| _public_functions_ | _field_ | Merkle root of the public function tree. |
| _unconstrained_functions_ | _field_ | Merkle root of the unconstrained function tree. |

#### _TransactionContext_

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5 changes: 0 additions & 5 deletions yellow-paper/docs/circuits/private-kernel-inner.md
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Expand Up @@ -76,11 +76,6 @@ For the _call_context_ in the [public_inputs](./private-function.md#public-input
- The previous iteration must not be a static call:
- _`caller_context.is_static_call == false`_

4. If it is an internal call: _`call_stack_item.function_data.is_internal == true`_

- The _msg_sender_ of the current iteration must equal the _storage_contract_address_:
- _`call_context.msg_sender == call_context.storage_contract_address`_

#### Verifying the private function proof.

It verifies that the private function was executed successfully with the provided proof data, verification key, and the public inputs, sourced from _[private_inputs](#private-inputs).[private_call](#privatecall)_.
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