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Behind the Scenes

Let’s get into Behind the scenes of how the greeting gets transferred from the source chain to the target chain:

  1. Instruction and Payment Delivery: A user invokes HelloWormhole’s sendCrossChainGreeting function which triggers Wormhole Relayer contract’s sendPayloadToEvm function. This publishes the delivery instructions to the blockchain logs and pays the default delivery provider.

  2. Signature Collection: Guardians, who monitor wormhole-connected blockchains, sign the delivery instructions, creating a Verifiable Action Approval (VAA). Once 13 out of 19 guardians sign the VAA, it’s considered fully signed.

  3. Instruction Parsing: The Delivery Provider watches for its assigned VAAs, parses the delivery instructions off-chain, and calls the deliver endpoint on the Wormhole Relayer contract on the target chain.

  4. VAA Verification and Payload Transfer: The Wormhole Relayer contract verifies the signatures of the delivery VAA, parses the delivery instructions, and calls the receiveWormholeMessages endpoint of the target address with the payload.

  5. Message Processing: The HelloWormhole contract on the target chain then processes the received message, completing the cross-chain greeting transfer.