Z-DAG Developer Guide

Z-DAG is a patent-pending transaction technology implemented on the Syscoin blockchain that enables near-instant, low-cost transactions that are highly scalable. Z-DAGs transactional throughput has been audited by third party blockchain auditing firm Whiteblock, you can view their report here. For more technical information on Z-DAG refer to the Z-DAG Syscoin Community page or the Syscoin Z-DAG Whitepaper.

Z-DAG Basics

Z-DAG is an interactive protocol, meaning you can continue to check the Z-DAG status all the way up to the point of blockchain confirmation. In today's network conditions a minimum Z-DAG threshold of 10 seconds or later are typically secure (99.9999%). Within certain enterprise deployments lower Z-DAG thresholds can be considered secure dependent on network conditions.

A typical transaction workflow has 2 stages:

The transaction enters the mempool (unconfirmed).
The transaction is mined into a block (confirmed).

When using Z-DAG, there are 3 stages:

The transaction enters the mempool (unconfirmed).
After a predefined Z-DAG threshold time the interactive protocol is called and returns a Z-DAG status.
The transaction is mined into a block (confirmed).

When step 2 returns a Z-DAG status of 0 (after the Z-DAG threshold) that means the SPT can be re-spent without the risk of double-spends. Longer Z-DAG thresholds provide a higher level of security. When transactions are in a Z-DAG state available balance for re-spending should be determined using the Z-DAG balance.

Understanding Z-DAG Statuses

Z-DAG status is retrieved by the command assetallocationverifyzdag. The output will reflect one of the following status levels:

Status	Description
-1	NOT FOUND (transaction is already confirmed on-chain, or is not a Z-DAG transaction)
0	OK
1	WARNING (there are more spending balances than the current POW sender balance in the mempool. An active stance should be taken and perhaps a deeper analysis as to potential conflicts related to the sender.)
2	CRITICAL (an active double spend was detected. Any descendant asset allocations are flagged as dangerous and should wait for POW confirmation before proceeding.)

Using Z-DAG Balances

The available balance while use Z-DAG can be determined by calling assetallocationbalance. If balance and zdag_balance are the same, then display balance. If the balances differ that is an indication that Z-DAG is active for this transaction and it has not yet been confirmed by Proof of Work. In this scenario the zdag_balance should be used to indicate to the user their available balance.