Glossary

• $CRC$ - Cross Rollup Communication. The protocol and process that is outlined in the document.

• $CRC_{msg}$ - The bytes of data being communicated across rollups

• User - An actor that wants to transfer data between rollups via a $CRC_{msg}$

• Relayer - An actor that facilitates the data transfer between rollups

• L1 - The Ethereum mainnet used by the rollups for security and data availability

• $R_{Source}$ - Source Rollup. The roll-up that the user wants to send $CRC_{msg}$ from

• $R_{Destination}$ - Destination Rollup. The roll-up in which the user wants to receive the $CRC_{msg}$

• $C_{Source RollupState}$ - L1 Contract used to roll up the state of $R_{Source}$

• $C_{Dest Rollup State}$ - L1 Contract used to roll up the state of $R_{Destination}$

• $C_{L1 Light Client}$- Contract inside a rollup (either $R_{Source}$ or $R_{Destination}$) acting as a Light client for L1. Receives and Verifies the L1 state from the Relayer.

• $C_{Outbox}$ - Contract deployed on every $R_{Source}$storing the $CRC_{msg}$to be transferred from the Rollup

• $C_{Inbox}$- Contract deployed on every $R_{Destination}$ that receives $CRC_{msg}$and calls the recipient $App_{Dest Rollup}$

• $App_{Source Rollup}$ - Contract inside $R_{Source}$ providing some application-specific logic that relies on sending $CRC_{msg}$

• $App_{Dest Rollup}$- Contract inside $R_{Destination}$ providing some application-specific logic that relies on receiving $CRC_{msg}$

• $CRC_{Init}$ - The initial transaction for calling $C_{Outbox}$ on $R_{Source}$, executed by the user in order to initiate a message transfer

• $CRC_{State Relay}$ - The transaction that the Relayer executes calling the $C_{L1 Light Client}$ on $R_{Destination}$ in order to update and verify the latest state of L1

• $CRC_{Delivery}$ - The transaction that uses the L1 and by proxy the $R_{Source}$ state in order to prove and execute the application logic of the $CRC_{msg}$

• $CRC_{State Relay Ack}$ - The transaction executed by a Relayer in order to prove to

  $C_{Outbox}$ that he relayed a state so that $CRC_{msg}$ can be processed, thus being eligible for the fees locked by users for that service

• $CRC_{Delivery Ack}$ - The transaction executed by a Relayer in order to prove to $C_{Outbox}$ that he delivered the $CRC_{msg}$ to $R_{Destination}$ which was based on a relayed state using $CRC_{State Relay Ack}$ transaction

• $SNARK_{L1 State}$ - A SNARK verifying that the computation of a specific block header in L1 has been executed based on the Minimal Light Client Sync Protocol specification.