Introduction

What is Harmony?‌

Harmony is a fast and secure blockchain for decentralized applications. Our production mainnet supports 4 shards of 1000 nodes, producing blocks in 5 seconds with finality.

Our Effective Proof-of-Stake (EPoS) reduces centralization while supporting stake delegation, reward compounding and double-sign slashing.

Harmony aims to build an open network of nodes operated and governed by a large community. This node community is called Pangaea.

Are we decentralized yet? There’s no consensus without participation. There are now 1,000 Harmony nodes – so far 640 of them run by the community – in line with thousands of Bitcoin and Ethereum nodes. Harmony consists of volunteers and validators from more than 100 countries and most of them have never run a node before.

Secure, Random State Sharding

Harmony has transcended the blockchain trilemma by bringing the best research to production. Sharding is proven to scale blockchains without compromising security and decentralization.

We divide not only our network nodes but also the blockchain states into shards, scaling linearly in all three aspects of machines, transactions and storages.

To prevent single shard attacks, we must have a sufficiently large number of nodes per shard and cryptographic randomness to re-shard regularly. Each shard has 250 nodes for strong security guarantee against Byzantine behaviors. We use Verifiable Random Function (VDF) for unbiasable and unpredictable shard membership.

Fast Consensus w/ Instant Finality

Harmony has innovated on the battle-tested Practical Byzantine Fault Tolerance (PBFT) for fast consensus of block transactions. Our Fast BFT (FBFT) leads to low transaction fees and 1-block-time finality in Harmony Mainnet.

We use Boneh–Lynn–Shacham (BLS) constant-sized signatures to commit blocks in a single round of consensus messages. We achieve 8-second block time with view changes in production against adversarial or unavailable leaders.

Harmony Mainnet was launched in June 2019. Our network has produced 10M+ blocks with 20k+ transactions in publicly traded, native ONE tokens.

Effective PoS & Token Economics

Harmony has designed a novel Proof-of-Stake (PoS) mechanism for network security and economics. Our Effective Proof-of-Stake (EPoS) reduces centralization and distributes rewards fairly to thousands of validators.

Our staking mechanism supports delegation and reward compounding. To support 100% uptime but fully open participation, EPoS slashes validators who double-sign and it penalizes elected but unavailable nodes.

Harmony Economics Model caps the annual insurance at 441 million tokens (about 3% rate in long term). Our model gives validators a simple and predictable return. All transaction fees are burnt to offset the insurance, naturally leading to zero inflation when our network usage becomes high.