Grid computing and blockchains

A grid is a network of many computers (called nodes), spread over different places and of different kinds, which temporarily join together to solve one large task. Together they act like a virtual supercomputer. Grids handle problems that need huge computing power, such as climate modelling and drug discovery. Unlike the cloud, which provides services to many users, a grid is set up for a particular application.

Grids are of two types:

• A data grid manages large amounts of data spread across many places, shared by many users.
• A CPU (processor) grid splits one big task among many PCs, which work on their parts at the same time (parallel processing).

Special software called middleware, such as the open-source Globus toolkit, is used to build grids.

Traditional transactions (bank records, land records) are kept in one central database. If it is hacked or lost, everything is at risk.

A blockchain is a decentralised, shared database. Every participating node keeps a full copy of the ledger (the record of transactions), and the ledger is 'append only': new records can be added, but old ones cannot be changed.

Data is stored in blocks. Each block is a secured chunk of data, or one valid transaction. Its header is visible to everyone, but its private data only to its owner. A new block is added only after all the nodes have checked and approved the transaction. So no single member can secretly alter the data.

Uses of blockchain: digital currency (the most popular use), sharing healthcare records, land registration records, voting systems, banking, media, telecom, travel and governance.