Introducing Harmony, the next generation sharding-based blockchain that is fully scalable, provably secure, and energy efficient. Harmony addresses the problems of existing
blockchains by combining the best research results and engineering practice in an optimally tuned system.
Specifically, Harmony makes breakthroughs in following aspects:
Harmony shards not only the network communication and transaction validation like Zilliqa, but also shards the blockchain state. This makes Harmony a fully scalable blockchain.
Harmony’s sharding process is provably secure thanks to the distributed randomness generation (DRG) process which is unpredictable, unbiaseable, verifiable and scalable. Harmony also reshards the network in a non-interruptive manner to prevent against slowly adaptive byzantine adversaries.
Unlike other sharding-based blockchains which require PoW to select validators, Harmony is based on PoS and thus energy efficient. Consensus is reached with a linearly scalable BFT algorithm that’s 100 times faster than PBFT.
The threshold of stakes required for a node to join the network is adjusted based on the volume of total staking in a way that malicious stakers cannot concentrate their power in a single shard. Moreover, the threshold is low enough so that small stakers can still participate in the network and earn rewards.
With RaptorQ fountain code, Harmony can propagate blocks quickly within shards or across network by using the Adaptive Information Dispersal Algorithm. Harmony also adopts Kademlia routing to achieve cross-shard transactions that scale logarithmically with the number of shards.
Harmony supports cross-shard transactions with shards directly communicating with each other. An atomic locking mechanism is used to ensure the consistency of cross-shard transactions.
By innovating on both the protocol and network layers, Harmony provides the world with a scalable and secure blockchain system that is able to support the emerging decentralized economy.
Harmony will enable applications which were not previously feasible on blockchain, including high-volume decentralized exchanges, interactive fair games, Visa-scale payment systems, and Internet-of-Things transactions.
Harmony strives to scale trust for billions of people and create a radically fair economy.
Blockchain sharding as a scalability solution has gained lots of attention since late 2017. Various sharding solutions have been proposed both in industry and academia.
Harmony draws inspiration from these three previous solutions and designs a PoS-based full sharding scheme that’s linearly scalable and provably secure. Harmony contains a beacon chain and multiple shard chains. The beacon chain serves as the randomness beacon and identity register, while the shard chains store separate blockchain states and process transactions concurrently.
Harmony proposes an efficient algorithm for randomness generation by combining Verifiable Random Function (VRF) and Verifiable Delay Function (VDF). Harmony also incorporates PoS in the sharding process which shifts the security consideration of a shard from the minimum number of nodes to the minimum number of voting shares.
After the successful commitment of a block, a protocol-defined number of new tokens will be rewarded to all validators who signed the block in proportion to their voting shares. The transactions fees are rewarded to validators similarly.
For any misbehaviors detected by the network, a certain amount of staked tokens will be slashed.
For example, if a leader failed to finish the consensus process and triggered the leader change process, P vote staked tokens will be slashed. If validators are proven to sign a dishonest block, all of their stake under the same shard will be slashed.
This severe punishment is meant to strongly discourage any dishonest behavior and make the network as secure as possible.
A proof of misbehavior can be two signed blocks that conflict with each other. Any validator can submit a transaction to prove the misbehavior of other validator and if verified, the slashed token will be rewarded to the prover(s).
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