Blockchain's objective was to make transactions non-repudiable and > they succeeded. However, that interacts with its decentralized
nature to make those transactions irreversible as well.
To re-use your example, banks don't "delete" the record of the bad check, they just create an offsetting journal entry, as both records are important to preserve. A transaction ledger is supposed to authenticate *every* transaction, and if you need to create an offsetting transaction, you do so in the same manner, and process the result in your code .. but the "bad" transaction DID happen as did your "deletion" of it, and as such, both actions are recorded. To apply to a real-world example .. Betty votes for X, but it's later determined that Betty was ineligible because (whatever). Betty's vote is recorded, as is the administrative cancellation thereof. It's critical that both transactions be recorded, attributed, non-reputeable. The system isn't designed to prevent fraud *itself*, it's designed to prevent alteration of the ledger. Regards, Michael Holstein CISSP Mgr. Network & Data Security Cleveland State University