<http://www.defenseone.com/technology/2016/05/nato-and-pentagon-want-get-thei...> 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. The two are looking at different implementations. The DoD’s Defense Advanced Research Projects Agency, or DARPA, wants to use blockchain to create a secure messaging service. The group recently put out a public request for pitches on the project, and wants a web or native messaging app to help secure communications between different departments and even potentially troops in combat. NATO is looking at more traditional uses—using blockchains to make military logistics, procurement, and finance more efficient.