What is blockchain
A blockchain is a growing list of records, called blocks, that are linked using cryptography. Each consequent block contains a cryptographic hash of the previous block, a timestamp, and transaction data.
Blockchain is by design resistant to modification of the data. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which requires consensus of the network majority. Although blockchain records are not completely unalterable, they are considered secure by design and exemplify a distributed computing system
Why is Revain using it
Companies often manipulate their reviews by publishing only the ones with high ratings while removing the bad ones. Revain uses the benefits of blockchain to make it impossible to either remove or alter reviews. To achieve that, the reviews are stored on the blockchain. Revain uses Bitcoin as the most reliable blockchain.
How it is implemented at Revain
Each review, each user's action or comment has its own unique hash. This hash is then written in a blockchain as a part of a block and may not be modified afterward.
If the review gets changed in any way, its new hash will not match the hash of the original review written in blockchain and the entire chain becomes inconsistent.
To validate the hashes, you can go to the blockchain page, open any block, find the review or action, calculate their hash by means of any 3rd party independent tool and compare it with 'Action hash' to make sure they match.