L2 Interop - Simplified Roadmap

Intended as a high-level summary. Many of the below items can be done in parallel.

User Stories:

1. Cross-chain sends:
   • Users should be able to send assets from any chain to any other chain in less than 3 slots (of the slower chain)
     • examples:
       • to/from L1: 12 * 3 = 36 seconds
       • between Arbitrum and Optimism: 2 * 3 = 6 seconds
2. Chain-specific payment requests:
   • Users should have an easy and standardized way to make a request of type: “send me X tokens of type Y on chain Z”.
     • Note: this supports 2 primary use cases: (i) person-to-person, and (ii) dapps requesting funds.
3. Updateable keys:
   • Users should be able to easily update the keys that control their smart contract wallet.
     • Short-term: updates should naturally propagate across chains
     • Medium-term: keystore -> updates only happen in one place
4. Verify chain directly:
   • Short-term: users should be able to verify the chain they are interacting with, rather than trust RPC providers.
   • Long-term: create general-purpose p2p network, so in principle no RPC providers required at all

Roadmap:

1. Cross-chain sends:
   • ERC-7785: On-chain configs
     • Need ERC to define common interface for on-chain config (solidity ABI the wallets would call)
     • Eventually include specification of state proof verification rules: ERC-3668
   • ERC-7828: chain-specific addresses
   • ERC-7683: cross-chain intents
   • RIP-7755: cross-chain calls
   • Shared bridges (down the road)
2. Chain-specific payment requests:
   • ERC to define
3. Updateable Keys:
   • Keystore wallets
     • See Scroll design
   • RIP-7728: L1SLOAD precompile
   • REMOTESTATICCALL
   • Cross-L2-replayable account state updates
4. Verify chain directly:
   • Cross-chain light clients
     • integrated into wallets
   • ERC-3668: secure off-chain data retrieval