Graph Aware Sync Protocol

Ragnar Friedman [e-mail]

Abstract

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.

Participants

• 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.

Notes

• 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.

Conclusion

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.