Graph Aware Sync Protocol

Ragnar Friedman


GASP is designed to synchronize transaction data between two parties in a blockchain environment. It ensures the legitimacy and completeness of transaction data using a recursive reconciliation method.


  • Alice: Initiates the sync process.

  • Bob: Responds and participates in the sync process.

Protocol Steps

  1. Initialization

    • Alice starts by sending a bloom filter containing all current spendable TXID+VOUTs as elements.

  2. Receiving and Building List

    • Bob receives the filter and builds a list of his items that are not members of the set.

  3. Transaction Verification

    • Bob sends an INV (Inventory) message to Alice for each item not in the set.

    • The INV includes:

      • Output, transaction, and associated merkle proof.

      • Any metadata (such as labels, descriptions, or local timestamps) associated with transactions or outputs.

      • A list of VOUTs spent by its inputs and associated metadata hashes.

      • The preimage for each hash, including all metadata and the merkle proof or broadcast response.

  4. Alice's Response

    • For each INV, Alice responds with a list of input transactions she does not know about.

    • If Alice has the transaction but the metadata hash differs, she requests updated metadata.

    • If Alice lacks the transaction, she requests the entire transaction.

  5. Recursive Transaction Sync

    • Bob responds to Alice's requests with an INV containing the encompassing transaction, done recursively.

      • When including the full transaction, all metadata is provided.

      • When only metadata is included, it encompasses the list of spent VOUTs and associated metadata hashes.

  6. Error Handling and Recovery

    • In case of errors, affected transactions are ignored and not synced.

    • If errors prevent a party from fully anchoring transactions back to the blockchain, these transactions are ignored.

    • Failures experienced by one party are not communicated to the other due to the declaratory nature of the protocol.

  7. Finalization of Sync

    • The process continues until there are no more INVs for Bob to send.

    • Once complete, all of Bob's records are considered synced with Alice.

  8. Role Reversal

    • The roles reverse, with Bob sending Alice a bloom filter.

    • The parties then exchange data in the other direction, following the same steps.

Security Measures

  • Verification of merkle proofs and the longest chain of block headers.

  • Recursively requesting information until all inputs are fully proven.

  • Invalidating transactions that cannot be linked back to a valid proof.


  • The protocol is adaptable to various blockchain environments.

  • The recursive nature ensures thorough and complete data synchronization.

  • The protocol emphasizes security, efficiency, and data integrity.


GASP offers a robust and secure method for synchronizing transaction data between parties in a blockchain network, leveraging recursive data exchange and thorough verification mechanisms.

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