How is CCTP Express different from Across
Being an intent-based bridge powered by fillers, CCTP Express is often compared with Across. How are we different?
The primary distinction between CCTP Express and Across lies in our positioning. While both protocols are intent-based bridges powered by fillers/relayers, CCTP Express is positioned to be a booster tool to use CCTP.
Given this focus, CCTP Express is closely integrated with CCTP and evolves in tandem with it. For instance, if CCTP supports EURC, CCTP Express will promptly support it as well.
And this alignment also applies to the choice of picking which chain CCTP Express supports. CCTP Express aims to cover all EVM and non-EVM chains CCTP operates. And like CCTP, CCTP Express adopts the bytes32address format, instead of the 20 byte address used in EVM, to handle 32 byte addresses in many non-EVM chains.
In contrast, Across is limited to EVM chains only, as it has a hard requirement to support EVM- chains only.
In CCTP Express, the Hub Pool smart contract utilizes the Iris attestation service used in CCTP to relay and verify messages. Deposit and Filled messages from various Spoke Pools are sent to Iris for attestation and then collected in the Hub Pool, which processes repayments on-chain.
In contrast, Across uses canonical bridges to relay messages and utilizes UMA to optimistically verify fill events off-chain. Since UMA works off-chain, an interval is needed as a dispute window.
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