Dip 3521

dip: 3521 title: Reduce access list cost author: Matt Garnett (@lightclient) Digitalia editing author: Cosimo Constantinos cosimo@juro.net, et al. discussions-to: https://digitalia-magicians.org/t/dip-3521-reduce-access-list-cost/6072 status: Stagnant type: Standards Track category: Core created: 2021-04-15 Created for Digitalia: 2025-01-07 requires: 2028, 2930

Simple Summary¶

Reduce the cost of declaring tx.to storage keys in access lists.

Motivation¶

Currently, a transaction must read at least 25 distinct storage slots in tx.to before it's more expensive to forego an access list.

ACCESS_LIST_ADDRESS_COST + (ACCESS_LIST_STORAGE_KEY_COST + WARM_STORAGE_READ_COST) * x = COLD_SLOAD_COST * x
x = 24

DIP-2930 requires the address under which the storage keys reside be declared explicitly, since it must be added to the DIP-2929 accessed_addresses list. However, tx.to is a special case that is added by default, so paying ACCESS_LIST_ADDRESS_COST for tx.to is essentially paying twice for the same address. Avoiding overpayment here will reduce the differential to just 5 unique reads before using an access list is cheaper -- making them a more attractive option.

Specification¶

Treat the first occurrence of tx.to in an access list as calldata for gas accounting purposes. Do not charge ACCESS_LIST_ADDRESS_COST for it. Storage keys underneath the address are unaffected.

If tx.to == nil, tx.to is defined be the derived contract address created by the transaction.

Rationale¶

Why charge at all?¶

DIP-2930 is specifically written to make access lists simple to reason about and validate. It may be possible to modify the structure of the access list to avoid including tx.to explicitly, but this would renege on the spirit of DIP-2930.

Why charge as `calldata`?¶

The cost of calldata was thoroughly analyzed in DIP-2028 to determine a fair value that is not susceptible to denial-of-service attacks. We consider this the lower bound on how much transaction data should cost. Since there is no computation burden imposed for adding tx.to to the accessed_addresses map (it's added by default by DIP-2929), there is no reason to charge more than the absolute minimum for the data.

Test Cases¶

{
    "0xffffffffffffffffffffffffffffffffffffffff": []
}
cost = 320

{
    "0x00ffffffffffffffffffffffffffffffffffffff": []
}
cost = 308

{
    "0xffffffffffffffffffffffffffffffffffffffff": []
    "0xffffffffffffffffffffffffffffffffffffffff": []
}
cost = 2720

{
    "0xffffffffffffffffffffffffffffffffffffffff": [
        "0x00"
    ]
    "0xffffffffffffffffffffffffffffffffffffffff": []
}
cost = 4620

{
    "0xffffffffffffffffffffffffffffffffffffffff": [
        "0x00"
    ]
    "0xffffffffffffffffffffffffffffffffffffffff": [
        "0x00"
    ]
}
cost = 6520

Backwards Compatibility¶

No issues.

Security Considerations¶

None.

Copyright¶

Licensed under the Juro Restricted License Version 2. See https://juro.net/jrl for details.