EIP-7702: Set EOA Account Code

July 16, 2024

As Solidity developers, we're always on the lookout for proposals that could significantly impact our smart contract development workflow. EIP-7702 represents a revolutionary step forward, bridging the gap between Externally Owned Accounts (EOAs) and smart contract wallets.

The Core Concept

EIP-7702 introduces a new transaction type that allows EOAs to temporarily set account code for a single transaction. This seemingly simple change opens up a world of possibilities for enhancing EOA functionality without sacrificing the simplicity that makes EOAs attractive to users.

New Transaction Type

The proposal introduces a new EIP-2718 transaction type, dubbed the "set code transaction." Here's what the RLP serialization looks like:

rlp([
    chain_id,
    nonce,
    max_priority_fee_per_gas,
    max_fee_per_gas,
    gas_limit,
    destination,
    value,
    data,
    access_list,
    authorization_list,
    signature_y_parity,
    signature_r,
    signature_s
])

The authorization_list is the key new element here, containing tuples of:

[chain_id, address, nonce, y_parity, r, s]

Technical Deep Dive

Delegation Designation

EIP-7702 introduces a "delegation designation" using the banned opcode 0xef from EIP-3541. The designation takes the form:

0xef0100 || address

This designation affects various instructions including:

  • EXTCODESIZE
  • EXTCODECOPY
  • EXTCODEHASH
  • CALL
  • CALLCODE
  • STATICCALL
  • DELEGATECALL

Gas Costs

The intrinsic cost builds on EIP-2930, with additional costs for the authorization list:

21000 + 16 * non-zero calldata bytes + 4 * zero calldata bytes +
1900 * access list storage key count + 2400 * access list address count +
PER_AUTH_BASE_COST * authorization list length

Where PER_AUTH_BASE_COST is set to 2500.

Implementation Benefits

New Possibilities

  1. Batching Operations

    • Perform multiple operations in one atomic transaction
    • Significantly improve gas efficiency for complex DApp interactions

  2. Transaction Sponsorship

    • Enable account X to pay for account Y's transaction
    • Open new possibilities for meta-transactions
    • Enhance gas abstraction capabilities

  3. Privilege De-escalation

    • Allow users to sign sub-keys with limited permissions
    • Enhance security in smart contract wallets

Security Considerations

When implementing delegate contracts, several security aspects need attention:

  1. Replay Protection

    • Implement and sign over a nonce in delegate contracts
    • Ensure transaction uniqueness

  2. Value Protection

    • Sign over the value field
    • Prevent unexpected effects in the callee

  3. Gas Protection

    • Sign over gas limits
    • Prevent potential griefing attacks

  4. Target/Calldata Protection

    • Sign over specific parameters
    • Prevent calling arbitrary functions in arbitrary contracts

Breaking Changes

The proposal introduces some notable changes to existing patterns:

  1. Account balance changes can now occur without direct account initiation
  2. EOA nonces may increase after transaction execution begins
  3. Potential impacts on mempool designs and inclusion lists

Future Implications

As we move towards "endgame account abstraction," EIP-7702 provides:

  • A pragmatic stepping stone for advanced EOA functionality
  • Backward compatibility with existing systems
  • Enhanced experimentation capabilities
  • Foundation for next-generation dApps

Conclusion

EIP-7702 marks a significant advancement in Ethereum's account model evolution. It provides developers with powerful new tools while maintaining backward compatibility. As we continue to build towards a more sophisticated blockchain ecosystem, proposals like EIP-7702 demonstrate how thoughtful protocol improvements can enhance both developer experience and end-user functionality.

The future of Ethereum development looks promising with such innovations, enabling more complex interactions while maintaining the security and simplicity that users expect from blockchain applications.