Integrity

Data Integrity is the maintenance of, and the assurance of, data accuracy and consistency over its entire life-cycle.

​​ Cryptography

The way it works is that the sender generates a Hash (see Hashing) of the data that it is sending. The sender then encrypts the Hash using his Private Key and sends both the data as well as the encrypted hash.

The recipient can calculate his own Hash from the data he received, decrypt the received Hash using the sender’s Public Key and compare both Hashes. If the Hashes are different, the data has been modified during transport. If they are not, there is a guarantee that it has not been modified.

​​ Quorum

A Quorum can be used to provide Data Integrity: if there are multiple instances of the data, then what the majority agrees on, is considered the Truth. This principle is applied in airplanes, clustered file systems, Blockchain, etc.

In order to prevent Split-Brain, there should always be an odd number of instances. (Otherwise, if 50% thinks it’s A, and 50% thinks it’s B, then you still don’t know, whereas if 67% thinks it’s A and 33% thinks it’s B, you know it’s A.)