Bitcoin: Guide on the blockchain. Part 10 - The Cryptonomist

Bitcoin (BTC)A Peer-to-Peer Electronic Cash System.

Bitcoin (BTC)A Peer-to-Peer Electronic Cash System.
  • Bitcoin (BTC) is a peer-to-peer cryptocurrency that aims to function as a means of exchange that is independent of any central authority. BTC can be transferred electronically in a secure, verifiable, and immutable way.
  • Launched in 2009, BTC is the first virtual currency to solve the double-spending issue by timestamping transactions before broadcasting them to all of the nodes in the Bitcoin network. The Bitcoin Protocol offered a solution to the Byzantine Generals’ Problem with a blockchain network structure, a notion first created by Stuart Haber and W. Scott Stornetta in 1991.
  • Bitcoin’s whitepaper was published pseudonymously in 2008 by an individual, or a group, with the pseudonym “Satoshi Nakamoto”, whose underlying identity has still not been verified.
  • The Bitcoin protocol uses an SHA-256d-based Proof-of-Work (PoW) algorithm to reach network consensus. Its network has a target block time of 10 minutes and a maximum supply of 21 million tokens, with a decaying token emission rate. To prevent fluctuation of the block time, the network’s block difficulty is re-adjusted through an algorithm based on the past 2016 block times.
  • With a block size limit capped at 1 megabyte, the Bitcoin Protocol has supported both the Lightning Network, a second-layer infrastructure for payment channels, and Segregated Witness, a soft-fork to increase the number of transactions on a block, as solutions to network scalability.

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1. What is Bitcoin (BTC)?

  • Bitcoin is a peer-to-peer cryptocurrency that aims to function as a means of exchange and is independent of any central authority. Bitcoins are transferred electronically in a secure, verifiable, and immutable way.
  • Network validators, whom are often referred to as miners, participate in the SHA-256d-based Proof-of-Work consensus mechanism to determine the next global state of the blockchain.
  • The Bitcoin protocol has a target block time of 10 minutes, and a maximum supply of 21 million tokens. The only way new bitcoins can be produced is when a block producer generates a new valid block.
  • The protocol has a token emission rate that halves every 210,000 blocks, or approximately every 4 years.
  • Unlike public blockchain infrastructures supporting the development of decentralized applications (Ethereum), the Bitcoin protocol is primarily used only for payments, and has only very limited support for smart contract-like functionalities (Bitcoin “Script” is mostly used to create certain conditions before bitcoins are used to be spent).

2. Bitcoin’s core features

For a more beginner’s introduction to Bitcoin, please visit Binance Academy’s guide to Bitcoin.

Unspent Transaction Output (UTXO) model

A UTXO transaction works like cash payment between two parties: Alice gives money to Bob and receives change (i.e., unspent amount). In comparison, blockchains like Ethereum rely on the account model.
https://preview.redd.it/t1j6anf8f3151.png?width=1601&format=png&auto=webp&s=33bd141d8f2136a6f32739c8cdc7aae2e04cbc47

Nakamoto consensus

In the Bitcoin network, anyone can join the network and become a bookkeeping service provider i.e., a validator. All validators are allowed in the race to become the block producer for the next block, yet only the first to complete a computationally heavy task will win. This feature is called Proof of Work (PoW).
The probability of any single validator to finish the task first is equal to the percentage of the total network computation power, or hash power, the validator has. For instance, a validator with 5% of the total network computation power will have a 5% chance of completing the task first, and therefore becoming the next block producer.
Since anyone can join the race, competition is prone to increase. In the early days, Bitcoin mining was mostly done by personal computer CPUs.
As of today, Bitcoin validators, or miners, have opted for dedicated and more powerful devices such as machines based on Application-Specific Integrated Circuit (“ASIC”).
Proof of Work secures the network as block producers must have spent resources external to the network (i.e., money to pay electricity), and can provide proof to other participants that they did so.
With various miners competing for block rewards, it becomes difficult for one single malicious party to gain network majority (defined as more than 51% of the network’s hash power in the Nakamoto consensus mechanism). The ability to rearrange transactions via 51% attacks indicates another feature of the Nakamoto consensus: the finality of transactions is only probabilistic.
Once a block is produced, it is then propagated by the block producer to all other validators to check on the validity of all transactions in that block. The block producer will receive rewards in the network’s native currency (i.e., bitcoin) as all validators approve the block and update their ledgers.

The blockchain

Block production

The Bitcoin protocol utilizes the Merkle tree data structure in order to organize hashes of numerous individual transactions into each block. This concept is named after Ralph Merkle, who patented it in 1979.
With the use of a Merkle tree, though each block might contain thousands of transactions, it will have the ability to combine all of their hashes and condense them into one, allowing efficient and secure verification of this group of transactions. This single hash called is a Merkle root, which is stored in the Block Header of a block. The Block Header also stores other meta information of a block, such as a hash of the previous Block Header, which enables blocks to be associated in a chain-like structure (hence the name “blockchain”).
An illustration of block production in the Bitcoin Protocol is demonstrated below.

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Block time and mining difficulty

Block time is the period required to create the next block in a network. As mentioned above, the node who solves the computationally intensive task will be allowed to produce the next block. Therefore, block time is directly correlated to the amount of time it takes for a node to find a solution to the task. The Bitcoin protocol sets a target block time of 10 minutes, and attempts to achieve this by introducing a variable named mining difficulty.
Mining difficulty refers to how difficult it is for the node to solve the computationally intensive task. If the network sets a high difficulty for the task, while miners have low computational power, which is often referred to as “hashrate”, it would statistically take longer for the nodes to get an answer for the task. If the difficulty is low, but miners have rather strong computational power, statistically, some nodes will be able to solve the task quickly.
Therefore, the 10 minute target block time is achieved by constantly and automatically adjusting the mining difficulty according to how much computational power there is amongst the nodes. The average block time of the network is evaluated after a certain number of blocks, and if it is greater than the expected block time, the difficulty level will decrease; if it is less than the expected block time, the difficulty level will increase.

What are orphan blocks?

In a PoW blockchain network, if the block time is too low, it would increase the likelihood of nodes producingorphan blocks, for which they would receive no reward. Orphan blocks are produced by nodes who solved the task but did not broadcast their results to the whole network the quickest due to network latency.
It takes time for a message to travel through a network, and it is entirely possible for 2 nodes to complete the task and start to broadcast their results to the network at roughly the same time, while one’s messages are received by all other nodes earlier as the node has low latency.
Imagine there is a network latency of 1 minute and a target block time of 2 minutes. A node could solve the task in around 1 minute but his message would take 1 minute to reach the rest of the nodes that are still working on the solution. While his message travels through the network, all the work done by all other nodes during that 1 minute, even if these nodes also complete the task, would go to waste. In this case, 50% of the computational power contributed to the network is wasted.
The percentage of wasted computational power would proportionally decrease if the mining difficulty were higher, as it would statistically take longer for miners to complete the task. In other words, if the mining difficulty, and therefore targeted block time is low, miners with powerful and often centralized mining facilities would get a higher chance of becoming the block producer, while the participation of weaker miners would become in vain. This introduces possible centralization and weakens the overall security of the network.
However, given a limited amount of transactions that can be stored in a block, making the block time too longwould decrease the number of transactions the network can process per second, negatively affecting network scalability.

3. Bitcoin’s additional features

Segregated Witness (SegWit)

Segregated Witness, often abbreviated as SegWit, is a protocol upgrade proposal that went live in August 2017.
SegWit separates witness signatures from transaction-related data. Witness signatures in legacy Bitcoin blocks often take more than 50% of the block size. By removing witness signatures from the transaction block, this protocol upgrade effectively increases the number of transactions that can be stored in a single block, enabling the network to handle more transactions per second. As a result, SegWit increases the scalability of Nakamoto consensus-based blockchain networks like Bitcoin and Litecoin.
SegWit also makes transactions cheaper. Since transaction fees are derived from how much data is being processed by the block producer, the more transactions that can be stored in a 1MB block, the cheaper individual transactions become.
https://preview.redd.it/depya70mf3151.png?width=1601&format=png&auto=webp&s=a6499aa2131fbf347f8ffd812930b2f7d66be48e
The legacy Bitcoin block has a block size limit of 1 megabyte, and any change on the block size would require a network hard-fork. On August 1st 2017, the first hard-fork occurred, leading to the creation of Bitcoin Cash (“BCH”), which introduced an 8 megabyte block size limit.
Conversely, Segregated Witness was a soft-fork: it never changed the transaction block size limit of the network. Instead, it added an extended block with an upper limit of 3 megabytes, which contains solely witness signatures, to the 1 megabyte block that contains only transaction data. This new block type can be processed even by nodes that have not completed the SegWit protocol upgrade.
Furthermore, the separation of witness signatures from transaction data solves the malleability issue with the original Bitcoin protocol. Without Segregated Witness, these signatures could be altered before the block is validated by miners. Indeed, alterations can be done in such a way that if the system does a mathematical check, the signature would still be valid. However, since the values in the signature are changed, the two signatures would create vastly different hash values.
For instance, if a witness signature states “6,” it has a mathematical value of 6, and would create a hash value of 12345. However, if the witness signature were changed to “06”, it would maintain a mathematical value of 6 while creating a (faulty) hash value of 67890.
Since the mathematical values are the same, the altered signature remains a valid signature. This would create a bookkeeping issue, as transactions in Nakamoto consensus-based blockchain networks are documented with these hash values, or transaction IDs. Effectively, one can alter a transaction ID to a new one, and the new ID can still be valid.
This can create many issues, as illustrated in the below example:
  1. Alice sends Bob 1 BTC, and Bob sends Merchant Carol this 1 BTC for some goods.
  2. Bob sends Carols this 1 BTC, while the transaction from Alice to Bob is not yet validated. Carol sees this incoming transaction of 1 BTC to him, and immediately ships goods to B.
  3. At the moment, the transaction from Alice to Bob is still not confirmed by the network, and Bob can change the witness signature, therefore changing this transaction ID from 12345 to 67890.
  4. Now Carol will not receive his 1 BTC, as the network looks for transaction 12345 to ensure that Bob’s wallet balance is valid.
  5. As this particular transaction ID changed from 12345 to 67890, the transaction from Bob to Carol will fail, and Bob will get his goods while still holding his BTC.
With the Segregated Witness upgrade, such instances can not happen again. This is because the witness signatures are moved outside of the transaction block into an extended block, and altering the witness signature won’t affect the transaction ID.
Since the transaction malleability issue is fixed, Segregated Witness also enables the proper functioning of second-layer scalability solutions on the Bitcoin protocol, such as the Lightning Network.

Lightning Network

Lightning Network is a second-layer micropayment solution for scalability.
Specifically, Lightning Network aims to enable near-instant and low-cost payments between merchants and customers that wish to use bitcoins.
Lightning Network was conceptualized in a whitepaper by Joseph Poon and Thaddeus Dryja in 2015. Since then, it has been implemented by multiple companies. The most prominent of them include Blockstream, Lightning Labs, and ACINQ.
A list of curated resources relevant to Lightning Network can be found here.
In the Lightning Network, if a customer wishes to transact with a merchant, both of them need to open a payment channel, which operates off the Bitcoin blockchain (i.e., off-chain vs. on-chain). None of the transaction details from this payment channel are recorded on the blockchain, and only when the channel is closed will the end result of both party’s wallet balances be updated to the blockchain. The blockchain only serves as a settlement layer for Lightning transactions.
Since all transactions done via the payment channel are conducted independently of the Nakamoto consensus, both parties involved in transactions do not need to wait for network confirmation on transactions. Instead, transacting parties would pay transaction fees to Bitcoin miners only when they decide to close the channel.
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One limitation to the Lightning Network is that it requires a person to be online to receive transactions attributing towards him. Another limitation in user experience could be that one needs to lock up some funds every time he wishes to open a payment channel, and is only able to use that fund within the channel.
However, this does not mean he needs to create new channels every time he wishes to transact with a different person on the Lightning Network. If Alice wants to send money to Carol, but they do not have a payment channel open, they can ask Bob, who has payment channels open to both Alice and Carol, to help make that transaction. Alice will be able to send funds to Bob, and Bob to Carol. Hence, the number of “payment hubs” (i.e., Bob in the previous example) correlates with both the convenience and the usability of the Lightning Network for real-world applications.

Schnorr Signature upgrade proposal

Elliptic Curve Digital Signature Algorithm (“ECDSA”) signatures are used to sign transactions on the Bitcoin blockchain.
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However, many developers now advocate for replacing ECDSA with Schnorr Signature. Once Schnorr Signatures are implemented, multiple parties can collaborate in producing a signature that is valid for the sum of their public keys.
This would primarily be beneficial for network scalability. When multiple addresses were to conduct transactions to a single address, each transaction would require their own signature. With Schnorr Signature, all these signatures would be combined into one. As a result, the network would be able to store more transactions in a single block.
https://preview.redd.it/axg3wayag3151.png?width=1601&format=png&auto=webp&s=93d958fa6b0e623caa82ca71fe457b4daa88c71e
The reduced size in signatures implies a reduced cost on transaction fees. The group of senders can split the transaction fees for that one group signature, instead of paying for one personal signature individually.
Schnorr Signature also improves network privacy and token fungibility. A third-party observer will not be able to detect if a user is sending a multi-signature transaction, since the signature will be in the same format as a single-signature transaction.

4. Economics and supply distribution

The Bitcoin protocol utilizes the Nakamoto consensus, and nodes validate blocks via Proof-of-Work mining. The bitcoin token was not pre-mined, and has a maximum supply of 21 million. The initial reward for a block was 50 BTC per block. Block mining rewards halve every 210,000 blocks. Since the average time for block production on the blockchain is 10 minutes, it implies that the block reward halving events will approximately take place every 4 years.
As of May 12th 2020, the block mining rewards are 6.25 BTC per block. Transaction fees also represent a minor revenue stream for miners.
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Weekly Dev Update #14

Weekly Dev Update #14

THORChain Weekly Dev Update for Week 22–28 Oct 2019

![](https://miro.medium.com/max/3352/1*TsS95GJsfPJqflMuTo6GLw.png)

BEPSwap Goes Cross-chain

BEPSwap is THORChain’s first go-to market product, built on a statechain to Binance Chain. BEPSwap was intended to only support BEP2 assets to minimise complexity with external chains. Two recent breakthroughs made by the THORChain development team in how to consider the cross-chain environment, as well as increasing the number of consensus participants, mean the team have now re-considered the scope of mainnet launch. Instead of launching the BEPSwap chain and decommissioning/hard-forking it into the THORChain mainnet, the team believe a network that supports cross-chain from the start can be built now. As such, THORChain will be launched, with support for Binance Chain, Bitcoin and Ethereum at Genesis. Binance Chain assets will be immediately supported, with Bitcoin and Ethereum enabled sometime in 2020. This will prevent large changes needing to occur post-mainnet launch. These two breakthroughs will be discussed in a future blog, but the team describe them as “Cross-chain Pools” and “Asynchronous Liquidity Delegation”.

Cross-chain Pools.

Cross-chain pools solve two key problems: 1. Security 2. User Experience. The first is that the network only holds assets that are in pools which are staked against Rune. This massively simpifies the attack surface of the network, since the network only needs to ensure that the amount of bonded Rune is always double the amount of staked Rune. This means that even if network participants could attack the network, they wouldn’t, because they can only steal 50% of what they bonded. Thus no rational actor would steal external assets. The second characteristic is the User Experience, in that neither pegged tokens, nor atomic swaps are used. Users who wish to swap BTC to ETH send in on-chain BTC, and will receive on-chain ETH immediately (and vice versa). The target speed for BTC->ETH will be 20 seconds. The target speed for ETH->BTC will be 10 minutes (1 block). Users who wish to stake, will stake on-chain BTC with on-chain Rune. Withdrawing their assets will mean they receive on-chain BTC and on-chain Rune. No pegging out, and no pegging in.

Asynchronous Liquidity Delegation.

The second breakthrough is how liquidity is managed in the system. The initial design had a single large Threshold Signature pool that held all the funds. While extremely secure, large committee memberships mean very long signing speeds (minutes for 67/100), which impacts the user experience. The team wish to target a signing speed of less than 5 seconds, which means TSS pools should be less than 11 participants. However, due to the incentive structure created by Cross-chain pools, no node has an incentive to steal assets — even if they were given individual custody of assets. This is because they are always bonding twice as much Rune as there is Rune staked in pools. A node that “exit-scams” the network is the equivalent to simply selling 50% of their bonded Rune to assets and leaving disorderly. The network can rebuild the pools by simply disbursing the node’s abandoned bond back into the pools, and churning in a new node. Thus it is resilient to even internal attacks. This setup even works for a node that goes offline — while offline they are unable to respond and they get “fined” from their bond for every transaction they couldn’t honour in a timely fashion. The final design is a large TSS pool that acts as a global custodian of bonded assets and incoming liquidity ( 22 of 33 is the initial target number), with 11 2 of 3 “satellite” pools which hold 50% of the staked assets. This means nodes can be delegated to asynchronously send out liquidity (swaps and withdrawals) with the signing speed of 2 of 3, but the security of 22 of 33. Over time, the team will target 200 of 300 nodes, with 100 2 of 3 satellite pools.

BEPSwap Development

The team are working on 4 parallel streams of effort. Cross-chain infrastructure has now been merged into a single repo called “THORNode”. 1. THORChain 2. Threshold Signature Scheme implementation 3. Front-end Integration for BEPSwap 4. Other development activities

StateChain

A lot of new work was done to make the statechain cross-chain, with agnostic treatment to chain data. The first three chains will be BNB, BTC and ETH. A global re-factor of naming conventions surrounding cross-chain assets was made. * Add chain to pools * Issue140 if the ticker and coin are the same , thus we don’t need to swap just refund * Issue150 add GAS result in a pool in suspended status * Auto-seed the development environment after a deploy. * Add Asset and Symbol common structs * Get stage seeding on nightly deploys. * Continue importing asset into thornode * Change coin.Denom to coin.Asset * Replace “Token” → “asset” * issue135 update stake logic to check ticker match coin * issue151 add cors support * Feature/docker compose updated build pipelines * Issue138 fix signer use wrong symbol issue , which cause issue with refund * Per chain gas policy * Remove binance specific logic * Choose rune asset based on mainnet vs testnet * Genesis ceremony * Added seed and smoke-test targets to .PHONY
![](https://miro.medium.com/max/3808/1*6HdyayI35M4ozW6s_eoGQQ.png) Assets will now be referred to as: CHAIN.SYMBOL

FrontEnd

Based on community feedback, the front-end is being refreshed. A lot of the past weeks updates were fixing small bugs and implementing the fresh design: * Resolve “Update theme variables and sizes” * Resolve “Update API endpoint with the prefix in the Front-End” * Resolve “Update Tab, Button, CoinButton component” * Resolve “BUG: Token amount selection doesn’t work properly in the Pool Stake” * Resolve “Update header, content layout” * Resolve “Build components for swap detail page” * Resolve “Implement Swap Detail Page” * Resolve “Fix issue for token amount input component”
![](https://miro.medium.com/max/4856/1*ozHbZXXLeCnvTGc0xNxNtQ.png) Swap Home Page
![](https://miro.medium.com/max/4784/1*8YY2dFqdCpO0opEICbQFtQ.png) Swap Detail View
![](https://miro.medium.com/max/2724/1*BYmhdcUgasfAmV9Yldu9bg.png) Swap Confirmation
![](https://miro.medium.com/max/3328/1*8pPD75MCcqaVFk1tZ4doCQ.png) Stake Detail View

Threshold Signature Scheme implementation

Work was done to clean up the code for peer-review, as well as implementing whitelisting for key-generation procedure. The TSS implementation is being integrated into the Statechain this week, in time to validate Asgard churn.

Whats Next?

To ship mainnet, the team are aiming for this:

Frontend:

Feature complete with excellent swapping and staking experience.

Chain Service:

Feature complete public RESTful API.

Statechain:

Feature complete with 22 of 33 Asgard, weekly churn, 2 of 3 satellite pools, asynchronous liquidity delegation and cross-chain support.

Timelines

The team are working for these milestones.

Other Development:

RUNEVault: July 2019 shipped Telegram Bot: August 2019 shipped Bep2Bot: August 2019 shipped

BEPSwap:

Testnet: August 2019 shipped Community Testing: shipped

THORChain:

Internal Freeze: 20 November 2019 on-time Audit: 20 December 2019 on-time Genesis: 03 January 2020 on-time

Community

To keep up to date, please monitor community channels, particularly Telegram and Twitter: * Twitter: https://twitter.com/thorchain_org * Telegram Community: https://t.me/thorchain_org * Telegram Announcements: https://t.me/thorchain * Reddit: https://reddit.com/thorchain * Github: https://github.com/thorchain * Medium: https://medium.com/thorchain
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QuarkChain FAQ

Part 1: Marketing Questions

  1. Q: There are so many blockchains these days and they are quite competitive. What plans does QuarkChain have in place to encourage the community to support this project continuously? A: We will continue to post our development process, ecosystem building and many more on our social media including Twitter, Telegram, Medium, Steemit, and Reddit. Except for previous 100+ volunteers helping us test our testnet, since our testnet 1.0 has been released, there are more than 3000 community members have joined the testing. We also have developer communities which are under development.
  2. Q: Can you introduce your partners? A: We have built strategic partnerships with 30+ global projects such as Tripio, Bodhi, and Laya.one. We also have plans to build deeper relationships with 10 projects including Covalent Chain, DxChain, Drep, Playtable, ValPromise, Ankr, MXC, LendChain, EON, and Celer. Besides, we also partner with Certik in Smart Contract audit. More partnership will be built.
  3. Q: What’s next in the roadmap? A: We will introduce our next plans in three major parts.
1)Development The first thing we need to do is to make sure our testnet is stable and keep optimizing our systems. We have found that there are many places, not only in scalability part but also in virtual machine and storage part, that we can improve in the following several months. We are also preparing articles of our technical details for open source several months later. We want to encourage community members to participate in our project and make our project not only our own project but also the community’s project. Another big thing we are focusing on currently is our mainnet which will be launched in several months. The main feature of the mainnet is that we can increase capacity on-demand as the network grows, and it will work as a scalable smart contract that can do whatever ETH can do but with greater scalability.
2)Marketing Currently, we only separate our market into Chinese, English, Korean, Japanese, Russian parts. We will have more strategies to open for different markets including, Thailand, Vietnam, Singapore, India and Europe. We will do more local stuff and enlarge our local community. Moreover, with the launch of testnet, we will build developer communities. At the beginning of August, we are going to hold the biggest hackathon in the Bay Area with Google ABC. There are only three projects to be selected and we are very honored to be one of them. At that time, there will be many programmers from big companies such as Google, Facebook and Linkedin building dApps on top of us on this two-day hackathon. We also have our 50 million eco-fund to establish an open and collaborative ecosystem of QuarkChain and 30 partners after just one month on Binance.
3)Korean Marketing We recently had the signing ceremony with a very strong insurance company in Korea who has revenue of 20 million per year and decides to go blockchain and global. We also have several contracts ready including a leading AI company and leading financial institution in Korea. You will hear more news about Korean marketing very soon.
  1. Q: Why the current circulating supply seems too low compared to the declared total 10 billion circulating supply? Please note that 40% QKC will be used for MINING and is already locked by Smart Contract. Private sale is locked to protect public sale investors. The first release of private sale is 10% and it will be released in about ONE MONTH after the QKC is listed on exchange. You could see the circulating supply schedule detail here: https://support.binance.com/hc/en-us/articles/360004471832-Binance-To-Open-Trading-For-QuarkChain-QKC-and-Risk-Warning Other token allocation includes 15% for the team, 15% for the foundation, and 5% for advisors. These are all locked up to 2 years with vesting plan using smart contract and will be unlocked gradually.

Part 2: Technical Questions

  1. Q: What kind of language is QuarkChain using for development? A: Currently, QuarkChain is developed in Python. The main reason for choosing Python is its fast deployment so that QuarkChain team could focus more on technology. Actually, we already obtain pretty decent performance results these days, and we could easily achieve much higher performance by employing other high-performance languages such as C++ and Go. Note that early Ethereum development also used Python, but later Go implementation becomes popular after Ethereum got more attention.
  2. Q: What does Collaborative Mining of QKC means? A: QuarkChain will utilize GPU-friendly mining algorithms, which is still under development. QuarkChain Network has several minor blockchains (shards) and one root blockchain. Each minor blockchain offers different incentives and difficulties. Miners could choose any minor blockchain at an optimal price of their hash power. This creates an open market economic model, where a blockchain is a seller with goods being the block reward, while a miner is a buyer with hash power being their currency. It is desirable that a marketing model is designed with features ensuring that though each party in the market pursues their interests, the collective behaviors of each party can benefit all. The goal of collaborative mining is to design incentive mechanisms and difficulty algorithms so that (1) Hash powers are incentivized to distribute evenly among shards. This ensures that all shards are mined evenly, and thus the system throughput (i.e., TPS) increases as the number of shards increases; (2) The root chain has a significantly large portion (over 50%) of hash power over the whole hash power of the network. This prevents double-spend attacks, and a malicious miner needs at least 50% * 50% = 25% power to perform an attack.
  3. Q: What is QuarkChain’s relationship with DAG or other Tangle technology? A: “The tangle is what is known as a directed acyclic graph (DAG): a data structure that moves in one direction without looping back onto itself. ” (from https://www.nasdaq.com/article/what-is-the-tangle-and-is-it-blockchains-next-evolutionary-step-cm911074) The system of QuarkChain Network itself can be treated as a well-structured DAG. This allows QuarkChain to inherit a lot of benefits from both blockchain and general DAG technique. For example, the consensus of QuarkChain and its threat model can be easily derived/analyzed following those of Bitcoin/Ethereum blockchain, while QuarkChain achieves high throughput similar to general DAG. Given two blockchains/DAGs of QuarkChain, we could easily tell which one should be appended thanks to QuarkChain’s root chain.
  4. Q: How does cross-shard communication work in QuarkChain? A: The QuarkChain Network fully supports cross-shard transactions as the first-class citizen, in a sense that: (1) Any user could issue any cross-shard transaction at any time; (2) Cross-shard transactions can be confirmed in minutes; (3) The throughput of cross-shard transactions could be scaled linearly as the number of shards increases. In short, the cross-shard transaction is almost the same as in-shard transaction except that the root chain needs to confirm the block header of the transaction before spending the output of the cross-shard transaction.
  5. Q: It seems there would be different nodes with different roles, all interconnected. How do you plan to prevent them from exploiting the role-playing model? As I understand it, you will manage and audit the network of voluntary nodes, then how do you call it “public blockchain”? Also, sharding doesn’t guarantee the persistence of data, nor completeness of the collection of shards. How do you guarantee longtail operation will be smooth and stable? What if there aren’t enough volunteers to participate? A: (1) For the first two questions, nodes (machines) trust each other to form a cluster acting as a full node. Anyone can run their cluster to participate in the network. Thus, we don’t manage clusters directly; (2) For the third question, there will be data completeness for an individual shard. Sharding and persistence are not mutually exclusive and we don’t understand why you think sharding doesn’t guarantee the persistence of data. All major data stored in Amazon, Facebook and Google use sharding to achieve scalability, and we are pretty sure persistence is guaranteed; (3) For the last question, mining is about incentives. We can try to solve the cold start problem by encouraging mining with relative greater incentives at the beginning.
  6. Q: Is that possible to say a dApp to seamlessly run on multiple shards if one shard cannot provide the necessary throughput? If that possible, as cross-shard transactions are slower, wouldn’t that create somewhat of a bottleneck as well? A: There is a topic of a scalable smart contract. We are working toward this feature, and a lot of interesting things are ongoing. Also, it depends on how the dApp is configured as well. Take CPU as an example, once Intel/AMD reached the clock speed limit, they realized multi-core should be the next design paradigm, which means performance software should also change the paradigm to fully leverage multi-core CPU architecture.
  7. Q: Number of Nodes — Can you explain to me if the more nodes, the better? Is that possible for QuarkChain to reach high TPS with fewer nodes (to prevent slower network)? A: It depends on how these nodes are organized. If all nodes would like to reach the same chain consensus, then the more nodes in the network, the slower the network is. Generally speaking, the more nodes in the network, the more decentralized the network is. Thus, we could achieve the high TPS with fewer nodes, but this will sacrifice decentralization, which is what we want to encourage. This shows the trade-off.
  8. Q: Number of shards — How does the number of shards are selected, how many nodes will be there in the number of shards? As per the white paper, each shard will have its difficulty and reward mechanism. How is it defined? So it means miners can switch over between the different shards depending on mining difficulty and can try to get maximum rewards? How is this mitigated? Is there any sort of EDA or there is a limitation for miners switching between shards? How is this more decentralized than usual PoW solution? A: The number of shards is determined by the network situation and could be done by our governance model. The miner could mine any shards, depending on block reward, difficulty, and network propagation of the major miners of the shard. More decentralized is mainly because a miner could mine a shard directly instead of joining a mining pool. The motivation for joining a mining pool is to collect reward timely as an exchange of transaction fee of pooling. By mining the shard directly (as the difficulty is lower), the miner could save transaction fee and encourage more decentralization.
  9. Q: Clustering — It is a good idea where the “honest nodes” are clustered to run as a supernode and will involve the root chain to confirm the transactions between them. There will be the incentive for the nodes to form clustering. How does this “Honest nodes” are selected for clustering or is it something which the nodes can do themselves? If they can do themselves? What prevents the malicious miners to collude and form a cluster of their own? How is this mitigated? A: A cluster is a replacement of a super-full node, but still serving as a peer in the network. Therefore, as long as there are sufficient peers (clusters) in the network, any blocks from the malicious cluster (peer) will be rejected. At the moment, a smart contract can be only administered in one shard. A cross-shard transaction is to transfer QKC from one shard to another shard, and thus a user with a single private key will be able to execute a smart contract transaction in any shard. A cluster — as a replacement of a super-full node — maintains the full ledger of the network and thus knows all chains. In addition, double spending attack is mitigated by root chain’s hash power via root-chain first consensus algorithm. Please refer our white paper for more details.
  10. Q: Does QuarkChain have any plans to move away from the EVM for dApps with many other VM’s coming out, such as NEO’s VM. Or do you intend to create your own VM? A: We may develop our own VM if needed, but this highly depends on the feedback of our dApps partners. Even though there are so many VMs, a lot of them lack systematic supports (such as editor, compiler, debugger). To our best knowledge, EVM is the most-adopted VM right now, and other candidates could be NEO VM, EOS VM, and ETH WASM. Currently, we don’t have the plan to swap VM but will add more supports for new VMs, i.e., adding new shards to support new VMs or even new consensus algorithms. This shows another advantage of our sharding technique on enabling this flexibility. In this situation, QKC will be the GAS, and other VMs may have different token models. We need to figure out the proper way to incorporate them. However, this should happen after the launch of mainnet.
You can find more about our technical details at https://steemit.com/technology/@quarkchain/response-to-the-article-quarkchain-red-flags-we-know-something-you-don-t-know We will also disclose more technical details on our series of post. You can check the first three of them on our official Medium at https://medium.com/quarkchain-official
Thank you for reading QuarkChain FAQ! The QuarkChain community appreciates your support!
Website https://www.quarkchain.io Telegram https://t.me/quarkchainio Twitter https://twitter.com/Quark_Chain Steemit https://steemit.com/@quarkchain Medium https://medium.com/quarkchain-official Reddit https://www.reddit.com/quarkchainio/ Weibo https://weibo.com/QuarkChain
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Bitcoin's Incentive Structure

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