Blockchain technology, the backbone of bitcoin, has a lot of applications. Finance firms want to use to cut down on administrative costs and trade faster. Estonia is using to securely track health records. Now it’s the military’s turn. Both the US Department of Defense (DoD) and NATO have put out requests for military-related apps built on blockchain, a decentralized digital ledger system. The ledger is stored in multiple copies across a large group and changes are sent out to all of them immediately, using a mathematical protocol that makes the ledger tamper-proof. That creates an immutable record of the information, and since everyone has a copy of the data, records are still safe even if a few people are hacked.