QuarkChain is a highly scalable blockchain that utilizes sharding to become a high-capacity peer-to-peer transactional network. QKC is designed as a multi-layer blockchain to enable peer-to-peer transactions through its digital coin, simply known as QKC.^[1] 

Overview

QuarkChain is a peer-to-peer network designed to process over100,000 TPS (more than a million initially, but the number dropped due to changes in project advertising strategy) thanks to its unique design and efficient data-distribution structure.^[2]

QCK uses sharding and is designed to meet the global commercial standards, be free of congestion, and deliver in high usage scenarios that require extra flexibility and speed. The network intends to become a high-throughput network for applications like distributed social media, high-frequency trading, IoT, payments, and gaming.^[3]

QKC began to separate the two main features of the chain into separate layers to find a solution that balances these two requirements.  The first layer contains any small blockchain or slice that processes a subset of all transactions independently. As the number of fragments increases, the number of transactions that can be processed simultaneously increases.^[1]

The second layer of QuarkChain is the "root chain". The default function of the root chain is to split the chain to check all blocks, but not to handle the transaction itself.^[2]

QuarkChain allows two types of transactions: Shard and Cross-Shard. Shard transactions occur between addresses of the same shard. But what sets QuarkChain apart from other high-throughput solutions is the ability to do cross-shade transactions.^[3]

To simplify the user experience of cross-shard systems, QuarkChain is developing a Smart Wallet. All addresses owned by users in all chassis can be accessed through a single private key. Theoretically, users can have many addresses related to different debris. To solve this problem, QuarkChain uses both the primary and secondary accounts within its wallet.^[1]

The primary account contains the address of the user's primary shard, and the secondary account manages the rest of the shard. To simplify fund management, transactions that run on a secondary account will revert the remaining accounts to the primary account. The user balance remains on the default account, eliminating the confusion caused by multiple balances across multiple chassis.^[2] 

The QuarkChain ICO token (QKC) is compatible with ERC-20 and distributed to the Ethereum blockchain. After the main networking starts in the fourth quarter of 2014, the ERC-20 token is converted to the main net token through pre-mining. Future QKC will be produced by miners. QKC is the only means of trading the value of the system and provides compensation for the miners. QuarkChain supports a smart deal on Ethereum Virtual Machine (EVM) to support future compatibility with existing apps, increasing scalability.^[3]

QuarkChain Token

QKC is a non-refundable functional utility token that will be used as the unit of exchange between participants on the QuarkChain Network and is designed to be used solely as the primary token on the network.^[1]

QKC is issued by the distributor as ERC20 standard-compliant digital tokens on the Ethereum blockchain. QKC may only be utilized on the QuarkChain network and ownership of QKC carries no right, express other than the right to use QKC as a means to enable usage of and interaction with the QuarkChain Network.^[2]

QKC is an integral and indispensable part of the QuarkChain Network, because, without QKC, there is no incentive for users to expand resources to participate in activities or provide service for the benefit of the entire ecosystem on the QuarkChain Network.^[3] 

Features of QuarkChain

The main features of QuarkChain are:

Reshardable two-layered blockchain. At the heart of QuarkChain are two layers of blockchains. One layer consists of sharding blockchains (shards), and the second one is a root blockchain. The root blockchain functions to confirm the blocks from the first layers. The second layer can be resharded without altering the root layer.^[1]

Market-driven collaborative mining:**** It ensures the security of all transactions using game theory incentives. Fundamentally, 50% of the hash power is allocated to the root chain, which prevents double spending on any transaction.^[2]

Anti-centralized horizontal scalability:**** Blockchains with high TPS typically lead to exorbitant super-full nodes. Such structure encourages mining centralization. QuarkChain tackles this issue by empowering multiple cheap nodes to form a super-full node.^[3]

Efficient cross-shard transactions: QuarkChain allows for quick cross-shard transactions that are confirmed in minutes and can be issued at any time. The cross-shard transaction speed correlates to amounts of shards on the network.^[1]

Turing-complete smart contracts:**** The system supports turing-complete smart contracts and Ethereum Virtual Machine (EVM) to allow smooth migration between EVM dapps and the QuarkChain platform. Therefore, any dapp built on Solidity and needs higher throughput can easily migrate to the platform.^[2]

QuarkChain Workability

QuarkChain is designed according to the following principles:

• Enhance scalability while ensuring decentralization and security

• Enable seamless cross-shard transactions for user quality of experience.

• Provide simple account management

• Develop an open standard to support various Dapps

• Create an incentive-driven ecosystem

QuarkChain separates between the state of the ledger and confirmation of transactions using a two-layered system - the Sharding layer which enables networks high throughput by distributing data, and the Root layer, which confirms the blocks mined by the shards.^[3]

The Elastic Sharding Layer: The sharding layer is a ledger that records the current ledger state, conducts transactions, and calculates results. Such functionality is data-intensive by design. Therefore, QuarkChain’s elastic sharding blockchain layer consists of minor blockchains (shards). Each shard processes subsets of all transactions independently, and shards can be increased or decreased on demand (thus elastic). These minor-blockchains fuel QuarkChain’s scalability and flexibility.^[1]

The Root Blockchain Layer: The second layer serves to confirm the transactions taking place on the network and mines the block to reach the desired mining difficulty. QuarkChain calls it the root blockchain. It confirms all the transactions from sharded blockchains. It doesn’t process any transactions itself and has sufficient mining difficulty to protect the blockchain.^[2]

Consensus Algorithm

QuarkChain is a hybrid Proof-of-Work (PoW) blockchain. It uses an ASIC-resistant PoW for mining and relies on “root chain first” consensus when dealing with forks. For example, if two forks were to happen on the root chain, the longest one would survive. If two forks were to occur on a shard, a node would compare their corresponding root chains before comparing forks. Again, the fork with the longer root chain would prevail.^[3]

Such consensus algorithm requires a double-spend attacker to make:

1. The minor blocks to revert the transaction.

2. A longer root chain fork with the minor block headers.

Nodes and Clusters : Mining on the QuarkChain platform consists of Nodes and Clusters. Nodes refer to powerful super-full nodes that are run by rigs and supercomputers, while Clusters are a collective of less powerful nodes that make up a super-full node together. Such a structure serves as an equalizer and even provides an edge to smaller players in the mining.^[1] 

QKC Exchange

QuarkChain is traded on exchanges like Binance. Over $6 million worth of QKC is traded daily and its trading pairs include ETH USDT, BTC, and XRP.^[2]