Bridging with StarkNet
- 1. Bridging with StarkNet February 2022 1 StarkNet edu team https://github.com/starknet-edu | @starkwareltd
- 2. Cross Chain Communication 2 @starkwareltd ● Today used for bridging assets: ○ Tokens/NFTs L1 <> L2 ○ Tokens/NFTs L1 <> L1
- 3. Cross Chain Communication 3 ● Tomorrow can we build more bridges? ○ Bridge permissions? ○ Bridge computation? ○ Bridge instructions? @starkwareltd
- 4. Cross Chain Communication 4 ● Can we build less bridges? ○ Let users pass data instead of assets ○ Let developers build their own bridges @starkwareltd
- 6. L2 -> L1 Messaging Status Description Submit Tx L2 Client sends TX ‘send_message_to_ l1’ TX initializes L2 Contract syscall to send message to L1 Contract Proof L2 TX including message included in Proof and verified on L1 State Update Message attached to state update, Core Contract increases counter, and ‘LogMessageToL1’ event emit Message Cleared L1 Recipient Contract can consume message in L1 TX via ‘consumeMessageFromL2’. Upon valid msg params counter decrement and message considered handled
- 8. 2. send_message_to_l1 8 ● Message is an array of felts, to a Recipient ● Recipient is a L1 account @starkwareltd
- 9. 3. Message registered 9 ● Message registered by StarkNet OS ● Message indexed by it’s hash @starkwareltd
- 11. 4. Message received on L1 11 ● StarkNet’s state is updated on Ethereum all ‘sent’ messages are updated as ‘pending’ ● Core Contracts increment message counter ● All message data can be retrieved for later use @starkwareltd
- 12. 4. Message consumed 12 ● Recipient should be calling StarkNet contract directly, but trigger can be arbitrary ● Counter decremented by 1 ● Full payload needs to be sent as calldata @starkwareltd
- 13. Delays 13 ● Messages are transmitted with proofs ● Proof verification frequency is currently every 2h on testnet ● This means your L2 -> L1 messages will be slow to debug! ● As usage of StarkNet picks up, this frequency may lower @starkwareltd
- 15. L1 -> L2 Messaging Status Description ‘sendMessageL2’ L1 Contract initiates a message w/ destination address. Core Contract hashes msg params + increases counter ‘l1_handler’ L2 Contract’s corresponding message handler is invoked Proof Handled message attached to proof of relevant state update State Update Message Consumption by L2 Contract included in State Update Message Cleared Initial counter is decrement and message considered handled
- 16. 1. sendMessageL2 16 ● Call the `sendMessageToL2` selector on the CCs ● Message is indexed and counter is incremented ● Specify the L2 recipient, as well as the function selector to call @starkwareltd
- 17. 2. l1_handler 17 ● After 10 block confs, your message is confed on StarkNet ● StarkNet initiates the corresponding L2 tx defined by the contracts ‘l1_handler’ @starkwareltd
- 18. 3. Prove it 18 ● The execution that takes place in the ‘l1_handler’ is added to the proof written back to L1 @starkwareltd
- 19. 4. State Update 19 ● The state is updated with the included ‘l1_handler’ execution @starkwareltd
- 20. 5. Message cleared 20 ● Message is now cleared from the Core Contracts storage ● Message is considered handled @starkwareltd
- 21. Why this is cool
- 22. Blockchains talking natively 22 ● No element of trust in the mechanism ● Ethereum has certainty of what happened on StarkNet ● Ethereum has mathematical proof that a message was sent @starkwareltd
- 23. Design your own protocol 23 ● No assumption about the payload sent (i.e. ‘payload_size=X’) ● Smart contracts on both sides can act upon data sent by L2 to move assets ● Assets can sit on any smart contract using the bridge ○ Tired of liquidity waiting in a bridge? ○ Design a bridge that has liquidity sitting on AAVE ○ Afraid of the security? ○ Implement a time lock on your bridge and select your own security @starkwareltd
- 24. Tight L1 integration 24 ● Full remote control: Send to a L1/L2 contract instructions for an arbitrary call ○ Recipient ○ Function selector ● L1 liquidity is StarkNet liquidity ○ You can use directly L1 assets in your applications @starkwareltd