Harmony is a layer-1 blockchain using sharding and Effective Proof of Stake to achieve scalability, security, and decentralization. The network was founded in 2018 by Stephen Tse with a mainnet launch in 2019.
Fully Scalable Architecture
Harmony’s sharding works not only on the network communication and transaction validation, but also on the blockchain state. This makes Harmony fully scalable on all three aspects of the blockchain: network, storage and transaction processing.
Secure Random Sharding
Harmony’s sharding process is provably secure against shard attacks because the network validators are randomly assigned and shuffled among shards. The randomness used in the sharding is obtained with a distributed randomness generation algorithm (based on VRF and VDF) which is unpredictable, un-biased, verifiable and scalable. Harmony reshards the network in a non-interruptive manner using “Cuckoo Rule” to prevent against slowly adaptive byzantine adversaries.
Efficient and Fast Consensus
Harmony’s consensus algorithm is called Fast Byzantine Fault Tolerance or FBFT. FBFT is a highly efficient and speedy consensus algorithm built upon the famous PBFT (Practical Byzantine Fault Tolerance) algorithm which is the cornerstone for distributed systems and consensus research for the past 30 years. Harmony’s FBFT is able to confirm blocks within 2 seconds thanks to the adoption of aggregated BLS (Boneh–Lynn–Shacham) signature. FBFT is also highly optimized in network message processing and block proposal pipelining so that the consensus can scale to hundreds of validators at the same time.
Unlike traditional blockchains which require PoW (Proof of Work) to reach consensus, Harmony is a Proof-of-Stake blockchain which is energy efficient and low-cost for node runners. The process to elect validators is called Effective Proof-of-Stake (EPoS) which is the first sharding-focused PoS mechanism that prevents stake centralization. In EPoS, validators with a large amount of staked tokens are obligated to run more nodes to support the network while validators with less stake run fewer nodes. Besides, EPoS is able to randomly and evenly distribute the stakes among all shards so no shard is less secure than other shards.
Scalable Networking Infrastructure
Harmony’s network layer is based on the industry-leading p2p protocol named Libp2p. We use Libp2p’s gossip protocol for network message broadcasting and stream protocol for decentralized state synchronization. To achieve high performance, we adopt RaptorQ fountain code and use Adaptive Information Dispersal Algorithm to quickly and efficiently broadcast large blocks. Harmony also features a design where Kademlia routing is used to achieve cross-shard transactions that scale logarithmically with the number of shards.
Asynchronous Cross-Shard Transactions
Harmony supports cross-shard transactions to achieve composability of assets and smart contracts between shards. We designed a receipt-based asynchronous cross-shard communication mechanism which achieves eventual consistency so no double-spending is possible between shards.
ONE Token 
ONE is the native token for Harmony which supports the monetary flow of the entire Harmony economic system. ONE has 18 decimals. The smallest unit of ONE is called Atto, which is 0.000000000000000001 ONE. (equivalent to Wei in Ethereum). The second smallest unit of ONE is called Nano, which is 0.000000001 ONE (equivalent to Gwei in Ethereum)
ONE token is the native token used for transacting on the Harmony blockchain. Users need to specify a certain amount of ONE so the transaction can be successfully processed and included in the blockchain.
Harmony is a Proof-of-Stake blockchain. Validator wallets are funded with 10,001 ONE. ONE token holders are also able to delegate their ONE tokens to existing validators to participate in the staking process. Elected validators who successfully sign blocks will receive block rewards in ONE tokens as compensation for their services.
Harmony is a permission-less and decentralized network which is governed by the community. Any protocol level decisions or improvements will be put as a proposal which will go through the open governance process to finalize. ONE is the only accepted token used as the measure for voting in the governance process.
- Harmony Forums https://docs.harmony.one/home/general/introduction/what-is-harmony
- Harmony One Forum https://docs.harmony.one/home/general/technology/tokenomics