SIP-7981: Increase Access List Cost

Price access lists for data to reduce maximum block size

Abstract

This SIP charges access lists for their data footprint, preventing the circumvention of the SIP-7623 floor pricing. This effectively reduces the worst-case block size by ~21% with minimal impact on users.

Motivation

Access lists are only priced for storage but not for their data.

Furthermore, access lists can circumvent the SIP-7623 floor pricing by contributing to SVM gas while still leaving a non-negligible data footprint. This enables achieving the maximal possible block size by combining access lists with calldata at a certain ratio.

Specification

Let access_list_bytes be the total byte count of addresses (20 bytes each) and storage keys (32 bytes each) in the access list.

Let access_list_data_cost = 64 * access_list_bytes (i.e. 1280 gas per address and 2048 gas per storage key). The 64 gas-per-byte rate matches the SIP-7976 calldata floor.

The access list data cost is added as a flat surcharge to the gas used calculation, leaving the SIP-2930 access_list_cost and the SIP-7976 floor calculation unchanged:

tx.gasUsed = (
    21000
    + access_list_data_cost
    +
    max(
        STANDARD_TOKEN_COST * tokens_in_calldata
        + execution_gas_used
        + isContractCreation * (32000 + INITCODE_WORD_COST * words(calldata))
        + access_list_cost,
        TOTAL_COST_FLOOR_PER_TOKEN * floor_tokens_in_calldata
    )
)

Any transaction with a gas limit below tx.gasUsed evaluated with execution_gas_used = 0 is considered invalid.

Rationale

Access list data is always charged at floor rate (added to access_list_cost), and access list tokens are included in the floor calculation. This ensures:

• Access list data always pays floor rate regardless of execution level
• Access lists cannot be used to bypass the calldata floor pricing
• Consistent pricing across all transaction data sources

Backwards Compatibility

This is a backwards incompatible gas repricing that requires a scheduled network upgrade.

Requires updates to gas estimation in wallets and nodes. Normal usage patterns remain largely unaffected.

Reference Implementation

def calculate_access_list_data_cost(access_list):
    """SIP-7981: flat 64 gas per byte of access list data."""
    # Each access entry: 20-byte address + 32 bytes per storage key
    total_bytes = sum(20 + 32 * len(access.slots) for access in access_list)
    return total_bytes * 64


def calculate_intrinsic_cost(tx):
    """
    Calculate intrinsic gas cost and floor gas cost.
    Both include the SIP-7981 access list data surcharge, so that
    tx.gasUsed = max(intrinsic_gas + execution_gas_used, floor_gas).
    """
    # Calldata tokens (SIP-7976)
    zero_bytes = count_zero_bytes(tx.data)
    nonzero_bytes = len(tx.data) - zero_bytes
    tokens_in_calldata = zero_bytes + nonzero_bytes * 4
    floor_tokens_in_calldata = len(tx.data) * 4

    # Access list cost (SIP-2930, unchanged) and SIP-7981 data surcharge
    access_list_cost = 0
    access_list_data_cost = 0
    if has_access_list(tx):
        for access in tx.access_list:
            access_list_cost += (
                ACCESS_LIST_ADDRESS_COST
                + len(access.slots) * ACCESS_LIST_STORAGE_KEY_COST
            )
        access_list_data_cost = calculate_access_list_data_cost(tx.access_list)

    # SIP-7976 floor (calldata only) plus SIP-7981 surcharge
    floor_gas = (
        TX_BASE_COST
        + floor_tokens_in_calldata * TOTAL_COST_FLOOR_PER_TOKEN
        + access_list_data_cost
    )

    # Intrinsic gas plus SIP-7981 surcharge
    calldata_cost = tokens_in_calldata * STANDARD_TOKEN_COST
    create_cost = TX_CREATE_COST + init_code_cost(tx.data) if is_create(tx) else 0
    intrinsic_gas = (
        TX_BASE_COST
        + calldata_cost
        + create_cost
        + access_list_cost
        + access_list_data_cost
    )

    return intrinsic_gas, floor_gas

Security Considerations

This SIP closes a loophole that allows circumventing SIP-7623 floor pricing. Without this fix, attackers can achieve larger blocks than intended by combining access lists with calldata. All transaction data sources now contribute to the floor calculation consistently.

Copyright

Copyright and related rights waived via CC0.

Citation

Please cite this document as:

Toni Wahrstätter (@nerolation), "SIP-7981: Increase Access List Cost [REVIEW]," Sila Improvement Proposals, no. 7981, December 2024. Available: https://sips.sila.org/SIPS/sip-7981.