Is blockchain tamper-proof?

The first of these controls is distribution and decentralisation: by ensuring that all interested parties have access to the ledger and any new transactions which are supposed to be added to it, tampering should become much more evident. If all of the parties involved have access to the same information, an attempt by anything less than a majority of stakeholders to incorrectly report a transaction will be noticed by all of the other parties who are processing the data honestly.

Without distribution and decentralisation – and therefore equal access to data for all interested parties – blockchain is no more tamper proof than any other data storage mechanism. A blockchain owned and exclusively processed by one individual, regardless of how many nodes they operate and how many people can read the data stored in the blockchain, could be tampered with by virtue of the fact that one individual controls all of the processing.

At this point, we need a method whereby the interested parties can communicate with each other and check the validity of a new block submitted to the chain. This is where implementations diverge. Historically, there have been three common approaches:

Proof of Work – Make calculating a valid hash for a block difficult to do, but easy for other parties to verify. The first person to calculate a valid hash submits it to the network and it is validated by the other parties prior to adding it to their chain. Well-Known Uses: Bitcoin (cryptocurrency); Monero (cryptocurrency)

Proof of Stake – Block creators are determined pseudo-randomly based on their ‘stake’ in the blockchain. This is primarily used by cryptocurrencies as the stake is easily calculated based on the amount of currency held by each member. Well-Known Uses: DASH (cryptocurrency); Ethereum (cryptocurrency, hybrid PoS/PoW)

Practical Byzantine Fault Tolerance – Something of a mouthful, PBFT is a consensus-based method of ‘tolerating’ faults in the data and recovering automatically. The specifics of the system are beyond the scope of this article. Well-Known Uses: Paraiba World

As an aside: all of the above are solutions to the risk of what is known as a that is, a fault where there is potentially imperfect or incomplete information which may result in the fault presenting differently to the various parties involved (consider that each party doesn’t know if or how many malicious participants there are and that some of these, while ‘in’ on any scheme to falsify data may only be malicious ‘approvers’ of bad data, not generators of it).