IOTA is an open-source distributed ledger protocol that goes 'beyond blockchain' through its core invention of the blockless ‘Tangle’. The IOTA Tangle is a quantum-proof Directed Acyclic Graph, with no fees on transactions & no fixed limit on how many transactions can be confirmed per second in the network. Instead, throughput grows in conjunction with activity in the network; the more activity, the faster the network. Unlike blockchain architecture, IOTA has no separation between users and validators; rather, validation is an intrinsic property of using the ledger, thus avoiding centralization. IOTA is initially focused on serving as the backbone of the emerging Internet-of-Things (IoT). For a more in depth look at the technical design of IOTA read their https://iota.org/IOTA_Whitepaper.pdf.

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