VeriBlock Bitcoin Finality Indicator ("vBFI")
Users of a VeriBlock-PoP-secured altchain can use the VeriBlock Bitcoin Finality Indicator (“vBFI”) to easily determine exactly when a transaction on an altchain network has as much (technically, more) security as a transaction on Bitcoin itself.
Proof-of-Proof (“PoP”) functions by incentivizing PoP miners to publish fingerprints of a security-inheriting blockchain to a security-providing blockchain in exchange for a reward.
In the event that an attacker attempts to reorganize the security-inheriting blockchain, the fork resolution protocol consults these previously-published fingerprints to determine whether the fork is valid or not.
To learn more, visit the wiki page How VeriBlock PoP vBFI Protects Altchains.