> For the complete documentation index, see [llms.txt](https://pijschain.gitbook.io/whitepaper/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://pijschain.gitbook.io/whitepaper/system-architecture/consensus-mechanism-pos/online-proof-mechanism.md).

# Online Proof Mechanism

PIJSChain uses a hybrid off-chain communication + on-chain aggregation model to efficiently prove the online status of staking nodes.

The process works as follows:

1. Heartbeat Broadcast\
   Staking nodes periodically broadcast BLS-signed heartbeat messages containing the epoch identifier, node index, and timestamp.<br>
2. BLS Aggregation\
   Block producers collect these heartbeat messages, verify signature validity, and aggregate them using BLS signature aggregation. This compresses many signatures into a single aggregate signature while updating the corresponding local online bitmap.<br>
3. Incremental Synchronization\
   Once a staking node has already been marked online within a given aggregation cycle, it does not need to repeatedly send heartbeat messages. This naturally reduces network overhead over time.<br>
4. On-Chain Finalization\
   The current block producer writes the aggregated signature and online bitmap into the block header and persists them via system calls to on-chain contracts.<br>
5. Final Consistency\
   The bitmap generated at the end of the epoch serves as the final online participation result. All nodes verify consistency through the shared stateRoot.<br>

This design allows PIJSChain to scale online participation proofs efficiently while preserving deterministic verifiability.


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