Horizon is built on a blockchain. Readers may be familiar with the Bitcoin crypto-currency which is also based on a blockchain.
We selected blockchain as a completely decentralized (peer-to-peer, P2P) tool we could use for discovery of previously unknown parties, and as a basis for trust among previously untrusted parties. Blockchain technologies:
At the time this project started Ethereum provided the best smart contract platform as well as a much lower transaction execution latency than the Bitcoin blockchain. However, we will continue to evaluate other blockchains as they become viable.