LP-3703: Statelessness Gas Costs

Abstract

This LP specifies gas cost changes required for Verkle tree state access, aligned with EIP-4762. These changes reflect the true cost of witness generation and verification in a stateless execution environment.

Motivation

Current gas costs assume state is in local storage. With Verkle trees and witnesses:

State access requires proof inclusion in witness
Witness size affects block propagation
Cold/warm distinction based on witness membership

Specification

Access Events

type AccessEvent struct {
    Address      common.Address
    StorageKey   common.Hash  // or nil for account access
    IsWrite      bool
    TreeIndex    uint64       // chunk in tree
}

Gas Schedule

Account Access

Operation	Cold	Warm
BALANCE	2600	100
EXTCODESIZE	2600	100
EXTCODEHASH	2600	100
EXTCODECOPY (per chunk)	2600	100

Storage Access

Operation	Cold	Warm
SLOAD	2100	100
SSTORE	2900	100

Code Access

Operation	Cold	Warm
First code chunk	2600	100
Each additional chunk	200	0

Witness Charging

func WitnessGas(accessList []AccessEvent) uint64 {
    gas := uint64(0)
    
    for _, event := range accessList {
        // Charge for tree branch traversal
        gas += WITNESS_BRANCH_COST  // 200
        
        // Charge for value in witness
        gas += WITNESS_VALUE_COST   // 100
        
        // Additional for writes
        if event.IsWrite {
            gas += WITNESS_WRITE_COST  // 100
        }
    }
    
    return gas
}

Block Witness Limits

const (
    // Maximum witness size in bytes
    MAX_WITNESS_SIZE = 1_000_000  // 1MB
    
    // Target witness size for gas adjustment
    TARGET_WITNESS_SIZE = 500_000 // 500KB
    
    // Witness gas per byte
    WITNESS_GAS_PER_BYTE = 16
)

EIP-2929 Compatibility

The access list mechanism from EIP-2929 extends:

type AccessList struct {
    Addresses   map[common.Address]struct{}
    Slots       map[common.Address]map[common.Hash]struct{}
    
    // NEW: Track witness chunks
    WitnessChunks map[uint64]struct{}
}

Rationale

Gas costs reflect:

Tree traversal cost (branch loading)
Proof size contribution
Write amplification in witness updates

Backwards Compatibility

Higher cold access costs may break some contracts
Warm access unchanged
Access lists reduce costs as before

Security Considerations

Witness size attacks mitigated by gas costs
Block limit provides hard cap
DoS via many cold accesses prevented

Statelessness Gas Costs (EIP-4762)