System of security using blockchain protocol

A data record structure adapted for transmission over a network; the data record generated on a network device participating in a Blockchain which has an device unique identifier; the data record structure containing at least a first record and a first unique identifier record; the first record containing data for transmission over the network to a device having a receiving device unique identifier; the first unique identifier record containing the device unique identifier. Also disclosed is a method of verification of identity of devices participating in a block chain; said Block chain comprising a plurality of ledgers held on a plurality of network devices; said network devices communicating contents of the ledgers between them over a network; said devices verifying the contents of the ledgers as part of the step of communicating the contents of the ledgers; said method comprising incorporating a unique identifier of a network device within the ledger maintained by the network device.