Hash trees are used in the IPFS, Btrfs and ZFS file systems, BitTorrent protocol, Dat protocol, Apache Wave protocol, Git and Mercurial distributed revision control systems, the Tahoe-LAFS backup system, the Bitcoin and Ethereum peer-to-peer networks, the Certificate Transparency framework, and a number of NoSQL systems like Apache Cassandra, Riak and Dynamo.
Hash trees are used in the IPFS, Btrfs and ZFS file systems, BitTorrent protocol, Dat protocol, Apache Wave protocol, Git and Mercurial distributed revision control systems, the Tahoe-LAFS backup system, the Bitcoin and Ethereum peer-to-peer networks, the Certificate Transparency framework, and a number of NoSQL systems like Apache Cassandra, Riak and Dynamo.
https://en.wikipedia.org/wiki/Merkle_tree