Private Function Circuit
Requirements
Private function circuits represent smart contract functions that can: privately read and modify leaves of the note hash tree and nullifier tree; perform computations on private data; and can be executed without revealing which function or contract has been executed.
The logic of each private function circuit is tailored to the needs of a particular application or scenario, but the public inputs of every private function circuit must adhere to a specific format. This specific format (often referred to as the "public inputs ABI for private functions") ensures that the private kernel circuits can correctly interpret the actions of every private function circuit.
Private Inputs
The private inputs of a private function circuit are customizable.
Public Inputs
The public inputs of every private function must adhere to the following ABI:
Field | Type | Description |
---|---|---|
call_context | CallContext | Context of the call corresponding to this function execution. |
args_hash | field | Hash of the function arguments. |
return_values | [field ; RETURN_VALUES_LENGTH ] | Return values of this function call. |
note_hashes | [NoteHash ; MAX_NEW_NOTE_HASHES_PER_CALL ] | New note hashes created in this function call. |
nullifiers | [Nullifier ; MAX_NEW_NULLIFIERS_PER_CALL ] | New nullifiers created in this function call. |
l2_to_l1_messages | [L2toL1Message ; MAX_NEW_L2_TO_L1_MSGS_PER_CALL ] | New L2 to L1 messages created in this function call. |
unencrypted_log_hashes | [UnencryptedLogHash ; MAX_UNENCRYPTED_LOG_HASHES_PER_CALL ] | Hashes of the unencrypted logs emitted in this function call. |
encrypted_log_hashes | [EncryptedLogHash ; MAX_ENCRYPTED_LOG_HASHES_PER_CALL ] | Hashes of the encrypted logs emitted in this function call. |
encrypted_note_preimage_hashes | [EncryptedNotePreimageHash ; MAX_ENCRYPTED_NOTE_PREIMAGE_HASHES_PER_CALL ] | Hashes of the encrypted note preimages emitted in this function call. |
note_hash_read_requests | [ReadRequest ; MAX_NOTE_HASH_READ_REQUESTS_PER_CALL ] | Requests to prove the note hashes being read exist. |
nullifier_read_requests | [ReadRequest ; MAX_NULLIFIER_READ_REQUESTS_PER_CALL ] | Requests to prove the nullifiers being read exist. |
key_validation_requests | [ParentSecretKeyValidationRequest ; MAX_KEY_VALIDATION_REQUESTS_PER_CALL ] | Requests to validate keys used in this function call. |
public_call_requests | [PublicCallRequest ; MAX_PUBLIC_CALL_STACK_LENGTH_PER_CALL ] | Requests to call public functions. |
private_call_requests | [PrivateCallRequest ; MAX_PRIVATE_CALL_STACK_LENGTH_PER_CALL ] | Requests to call Private functions. |
counter_start | u32 | Counter at which the function call was initiated. |
counter_end | u32 | Counter at which the function call ended. |
min_revertible_side_effect_counter | u32 | Counter below which the side effects are non-revertible. |
block_header | BlockHeader | Information about the trees used for the transaction. |
chain_id | field | Chain ID of the transaction. |
version | field | Version of the transaction. |
After generating a proof for a private function circuit, that proof (and associated public inputs) will be passed-into a private kernel circuit as private inputs. Private kernel circuits use the private function's proof, public inputs, and verification key, to verify the correct execution of the private function. Private kernel circuits then perform a number of checks and computations on the private function's public inputs.
Types
CallContext
Field | Type | Description |
---|---|---|
msg_sender | AztecAddress | Address of the caller contract. |
storage_contract_address | AztecAddress | Address of the contract against which all state changes will be stored. (It is not called contract_address , because in the context of delegate calls, that would be an ambiguous name.) |
portal_contract_address | AztecAddress | Address of the portal contract to the storage contract. |
is_delegate_call | bool | A flag indicating whether the call is a delegate call. |
is_static_call | bool | A flag indicating whether the call is a static call. |
GasSettings
Field | Type | Description |
---|---|---|
da.gas_limit | u32 | Total limit for DA gas for the transaction. |
da.teardown_gas_limit | u32 | Limit for DA gas specific to the teardown phase. |
da.max_fee_per_gas | field | Maximum amount that the sender is willing to pay per unit of DA gas. |
l2.gas_limit | u32 | Total limit for L2 gas for the transaction. |
l2.teardown_gas_limit | u32 | Limit for L2 gas specific to the teardown phase. |
l2.max_fee_per_gas | field | Maximum amount that the sender is willing to pay per unit of L2 gas. |
inclusion_fee | field | Flat fee the user pays for inclusion. |
NoteHash
Field | Type | Description |
---|---|---|
value | field | Hash of the note. |
counter | u32 | Counter at which the note hash was created. |
Nullifier
Field | Type | Description |
---|---|---|
value | field | Value of the nullifier. |
counter | u32 | Counter at which the nullifier was created. |
note_hash_counter | u32 | Counter of the transient note the nullifier is created for. 0 if the nullifier does not associate with a transient note. |
L2toL1Message
Field | Type | Description |
---|---|---|
value | field | L2-to-l2 message. |
counter | u32 | Counter at which the message was emitted. |
UnencryptedLogHash
Field | Type | Description |
---|---|---|
hash | field | Hash of the unencrypted log. |
length | field | Number of fields of the log preimage. |
counter | u32 | Counter at which the hash was emitted. |
EncryptedLogHash
Field | Type | Description |
---|---|---|
hash | field | Hash of the encrypted log. |
length | field | Number of fields of the log preimage. |
counter | u32 | Counter at which the hash was emitted. |
randomness | field | A random value to hide the contract address. |
EncryptedNotePreimageHash
Field | Type | Description |
---|---|---|
hash | field | Hash of the encrypted note preimage. |
length | field | Number of fields of the note preimage. |
counter | u32 | Counter at which the hash was emitted. |
note_hash_counter | u32 | Counter of the corresponding note hash. |
ReadRequest
Field | Type | Description |
---|---|---|
value | field | Value being read. |
contract_address | AztecAddress | Address of the contract the value was created. |
counter | u32 | Counter at which the request was made. |
ParentSecretKeyValidationRequest
Field | Type | Description |
---|---|---|
parent_public_key | GrumpkinPoint | Claimed parent public key of the secret key. |
hardened_child_secret_key | fq | Secret key passed to the function. |
PublicCallRequest
Field | Type | Description |
---|---|---|
call_stack_item_hash | field | Hash of the call stack item. |
counter | u32 | Counter at which the request was made. |
PrivateCallRequest
Field | Type | Description |
---|---|---|
call_stack_item_hash | field | Hash of the call stack item. |
counter_start | u32 | Counter at which the call was initiated. |
counter_end | u32 | Counter at which the call ended. |
BlockHeader
Field | Type | Description |
---|---|---|
note_hash_tree_root | field | Root of the note hash tree. |
nullifier_tree_root | field | Root of the nullifier tree. |
l1_to_l2_messages_tree_root | field | Root of the l1-to-l2 messages tree. |
public_data_tree_root | field | Root of the public data tree. |
archive_tree_root | field | Root of the state roots tree archived at the block prior to when the transaction was assembled. |
global_variables_hash | field | Hash of the previous global variables. |