This is a very basic visual introduction to the concept behind a blockchain. Anders Brownworth introduces the idea of an immutable ledger using an interactive web demo. If you are interested in playing with this on your own, it is available online at:
The code that runs this demo is also on GitHub:
A distributed ledger is essentially an asset database that can be shared across a network of multiple sites, geographies or institutions. All participants within a network can have their own identical copy of the ledger. Any changes to the ledger are reflected in all copies in minutes, or in some cases, seconds. The assets can be financial, legal, physical or electronic. The security and accuracy of the assets stored in the ledger are maintained cryptographically through the use of ‘keys’ and signatures to control who can do what within the shared ledger. Entries can also be updated by one, some or all of the participants, according to rules agreed by the network.
Full report: Distributed Ledger Technology: Beyond Block chain – by the UK Government Office for Science.