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How To End The Cryptocurrency Exchange "Wild West" Without Crippling Innovation


In case you haven't noticed the consultation paper, staff notice, and report on Quadriga, regulators are now clamping down on Canadian cryptocurrency exchanges. The OSC and other regulatory bodies are still interested in industry feedback. They have not put forward any official regulation yet. Below are some ideas/insights and a proposed framework.



Many of you have limited time to read the full proposal, so here are the highlights:

Offline Multi-Signature

Effective standards to prevent both internal and external theft. Exchange operators are trained and certified, and have a legal responsibility to users.

Regular Transparent Audits

Provides visibility to Canadians that their funds are fully backed on the exchange, while protecting privacy and sensitive platform information.

Insurance Requirements

Establishment of basic insurance standards/strategy, to expand over time. Removing risk to exchange users of any hot wallet theft.


Background and Justifications


Cold Storage Custody/Management
After reviewing close to 100 cases, all thefts tend to break down into more or less the same set of problems:
• Funds stored online or in a smart contract,
• Access controlled by one person or one system,
• 51% attacks (rare),
• Funds sent to the wrong address (also rare), or
• Some combination of the above.
For the first two cases, practical solutions exist and are widely implemented on exchanges already. Offline multi-signature solutions are already industry standard. No cases studied found an external theft or exit scam involving an offline multi-signature wallet implementation. Security can be further improved through minimum numbers of signatories, background checks, providing autonomy and legal protections to each signatory, establishing best practices, and a training/certification program.
The last two transaction risks occur more rarely, and have never resulted in a loss affecting the actual users of the exchange. In all cases to date where operators made the mistake, they've been fully covered by the exchange platforms.
• 51% attacks generally only occur on blockchains with less security. The most prominent cases have been Bitcoin Gold and Ethereum Classic. The simple solution is to enforce deposit limits and block delays such that a 51% attack is not cost-effective.
• The risk of transactions to incorrect addresses can be eliminated by a simple test transaction policy on large transactions. By sending a small amount of funds prior to any large withdrawals/transfers as a standard practice, the accuracy of the wallet address can be validated.
The proposal covers all loss cases and goes beyond, while avoiding significant additional costs, risks, and limitations which may be associated with other frameworks like SOC II.

On The Subject of Third Party Custodians
Many Canadian platforms are currently experimenting with third party custody. From the standpoint of the exchange operator, they can liberate themselves from some responsibility of custody, passing that off to someone else. For regulators, it puts crypto in similar categorization to oil, gold, and other commodities, with some common standards. Platform users would likely feel greater confidence if the custodian was a brand they recognized. If the custodian was knowledgeable and had a decent team that employed multi-sig, they could keep assets safe from internal theft. With the right protections in place, this could be a great solution for many exchanges, particularly those that lack the relevant experience or human resources for their own custody systems.
However, this system is vulnerable to anyone able to impersonate the exchange operators. You may have a situation where different employees who don't know each other that well are interacting between different companies (both the custodian and all their customers which presumably isn't just one exchange). A case study of what can go wrong in this type of environment might be Bitpay, where the CEO was tricked out of 5000 bitcoins over 3 separate payments by a series of emails sent legitimately from a breached computer of another company CEO. It's also still vulnerable to the platform being compromised, as in the really large $70M Bitfinex hack, where the third party Bitgo held one key in a multi-sig wallet. The hacker simply authorized the withdrawal using the same credentials as Bitfinex (requesting Bitgo to sign multiple withdrawal transactions). This succeeded even with the use of multi-sig and two heavily security-focused companies, due to the lack of human oversight (basically, hot wallet). Of course, you can learn from these cases and improve the security, but so can hackers improve their deception and at the end of the day, both of these would have been stopped by the much simpler solution of a qualified team who knew each other and employed multi-sig with properly protected keys. It's pretty hard to beat a human being who knows the business and the typical customer behaviour (or even knows their customers personally) at spotting fraud, and the proposed multi-sig means any hacker has to get through the scrutiny of 3 (or more) separate people, all of whom would have proper training including historical case studies.
There are strong arguments both for and against using use of third party custodians. The proposal sets mandatory minimum custody standards would apply regardless if the cold wallet signatories are exchange operators, independent custodians, or a mix of both.

On The Subject Of Insurance
ShakePay has taken the first steps into this new realm (congratulations). There is no question that crypto users could be better protected by the right insurance policies, and it certainly feels better to transact with insured platforms. The steps required to obtain insurance generally place attention in valuable security areas, and in this case included a review from CipherTrace. One of the key solutions in traditional finance comes from insurance from entities such as the CDIC.
However, historically, there wasn't found any actual insurance payout to any cryptocurrency exchange, and there are notable cases where insurance has not paid. With Bitpay, for example, the insurance agent refused because the issue happened to the third party CEO's computer instead of anything to do with Bitpay itself. With the Youbit exchange in South Korea, their insurance claim was denied, and the exchange ultimately ended up instead going bankrupt with all user's funds lost. To quote Matt Johnson in the original Lloyd's article: “You can create an insurance policy that protects no one – you know there are so many caveats to the policy that it’s not super protective.”
ShakePay's insurance was only reported to cover their cold storage, and “physical theft of the media where the private keys are held”. Physical theft has never, in the history of cryptocurrency exchange cases reviewed, been reported as the cause of loss. From the limited information of the article, ShakePay made it clear their funds are in the hands of a single US custodian, and at least part of their security strategy is to "decline[] to confirm the custodian’s name on the record". While this prevents scrutiny of the custodian, it's pretty silly to speculate that a reasonably competent hacking group couldn't determine who the custodian is. A far more common infiltration strategy historically would be social engineering, which has succeeded repeatedly. A hacker could trick their way into ShakePay's systems and request a fraudulent withdrawal, impersonate ShakePay and request the custodian to move funds, or socially engineer their way into the custodian to initiate the withdrawal of multiple accounts (a payout much larger than ShakePay) exploiting the standard procedures (for example, fraudulently initiating or override the wallet addresses of a real transfer). In each case, nothing was physically stolen and the loss is therefore not covered by insurance.
In order for any insurance to be effective, clear policies have to be established about what needs to be covered. Anything short of that gives Canadians false confidence that they are protected when they aren't in any meaningful way. At this time, the third party insurance market does not appear to provide adequate options or coverage, and effort is necessary to standardize custody standards, which is a likely first step in ultimately setting up an insurance framework.
A better solution compared to third party insurance providers might be for Canadian exchange operators to create their own collective insurance fund, or a specific federal organization similar to the CDIC. Such an organization would have a greater interest or obligation in paying out actual cases, and that would be it's purpose rather than maximizing it's own profit. This would be similar to the SAFU which Binance has launched, except it would cover multiple exchanges. There is little question whether the SAFU would pay out given a breach of Binance, and a similar argument could be made for a insurance fund managed by a collective of exchange operators or a government organization. While a third party insurance provider has the strong market incentive to provide the absolute minimum coverage and no market incentive to payout, an entity managed by exchange operators would have incentive to protect the reputation of exchange operators/the industry, and the government should have the interest of protecting Canadians.

On The Subject of Fractional Reserve
There is a long history of fractional reserve failures, from the first banks in ancient times, through the great depression (where hundreds of fractional reserve banks failed), right through to the 2008 banking collapse referenced in the first bitcoin block. The fractional reserve system allows banks to multiply the money supply far beyond the actual cash (or other assets) in existence, backed only by a system of debt obligations of others. Safely supporting a fractional reserve system is a topic of far greater complexity than can be addressed by a simple policy, and when it comes to cryptocurrency, there is presently no entity reasonably able to bail anyone out in the event of failure. Therefore, this framework is addressed around entities that aim to maintain 100% backing of funds.
There may be some firms that desire but have failed to maintain 100% backing. In this case, there are multiple solutions, including outside investment, merging with other exchanges, or enforcing a gradual restoration plan. All of these solutions are typically far better than shutting down the exchange, and there are multiple cases where they've been used successfully in the past.

Proof of Reserves/Transparency/Accountability
Canadians need to have visibility into the backing on an ongoing basis.
The best solution for crypto-assets is a Proof of Reserve. Such ideas go back all the way to 2013, before even Mt. Gox. However, no Canadian exchange has yet implemented such a system, and only a few international exchanges (CoinFloor in the UK being an example) have. Many firms like Kraken, BitBuy, and now ShakePay use the Proof of Reserve term to refer to lesser proofs which do not actually cryptographically prove the full backing of all user assets on the blockchain. In order for a Proof of Reserve to be effective, it must actually be a complete proof, and it needs to be understood by the public that is expected to use it. Many firms have expressed reservations about the level of transparency required in a complete Proof of Reserve (for example Kraken here). While a complete Proof of Reserves should be encouraged, and there are some solutions in the works (ie TxQuick), this is unlikely to be suitable universally for all exchange operators and users.
Given the limitations, and that firms also manage fiat assets, a more traditional audit process makes more sense. Some Canadian exchanges (CoinSquare, CoinBerry) have already subjected themselves to annual audits. However, these results are not presently shared publicly, and there is no guarantee over the process including all user assets or the integrity and independence of the auditor. The auditor has been typically not known, and in some cases, the identity of the auditor is protected by a NDA. Only in one case (BitBuy) was an actual report generated and publicly shared. There has been no attempt made to validate that user accounts provided during these audits have been complete or accurate. A fraudulent fractional exchange, or one which had suffered a breach they were unwilling to publicly accept (see CoinBene), could easily maintain a second set of books for auditors or simply exclude key accounts to pass an individual audit.
The proposed solution would see a reporting standard which includes at a minimum - percentage of backing for each asset relative to account balances and the nature of how those assets are stored, with ownership proven by the auditor. The auditor would also publicly provide a "hash list", which they independently generate from the accounts provided by the exchange. Every exchange user can then check their information against this public "hash list". A hash is a one-way form of encryption, which fully protects the private information, yet allows anyone who knows that information already to validate that it was included. Less experienced users can take advantage of public tools to calculate the hash from their information (provided by the exchange), and thus have certainty that the auditor received their full balance information. Easy instructions can be provided.
Auditors should be impartial, their identities and process public, and they should be rotated so that the same auditor is never used twice in a row. Balancing the cost of auditing against the needs for regular updates, a 6 month cycle likely makes the most sense.

Hot Wallet Management
The best solution for hot wallets is not to use them. CoinBerry reportedly uses multi-sig on all withdrawals, and Bitmex is an international example known for their structure devoid of hot wallets.
However, many platforms and customers desire fast withdrawal processes, and human validation has a cost of time and delay in this process.
A model of self-insurance or separate funds for hot wallets may be used in these cases. Under this model, a platform still has 100% of their client balance in cold storage and holds additional funds in hot wallets for quick withdrawal. Thus, the risk of those hot wallets is 100% on exchange operators and not affecting the exchange users. Since most platforms typically only have 1%-5% in hot wallets at any given time, it shouldn't be unreasonable to build/maintain these additional reserves over time using exchange fees or additional investment. Larger withdrawals would still be handled at regular intervals from the cold storage.
Hot wallet risks have historically posed a large risk and there is no established standard to guarantee secure hot wallets. When the government of South Korea dispatched security inspections to multiple exchanges, the results were still that 3 of them got hacked after the inspections. If standards develop such that an organization in the market is willing to insure the hot wallets, this could provide an acceptable alternative. Another option may be for multiple exchange operators to pool funds aside for a hot wallet insurance fund. Comprehensive coverage standards must be established and maintained for all hot wallet balances to make sure Canadians are adequately protected.

Current Draft Proposal

(1) Proper multi-signature cold wallet storage.
(a) Each private key is the personal and legal responsibility of one person - the “signatory”. Signatories have special rights and responsibilities to protect user assets. Signatories are trained and certified through a course covering (1) past hacking and fraud cases, (2) proper and secure key generation, and (3) proper safekeeping of private keys. All private keys must be generated and stored 100% offline by the signatory. If even one private keys is ever breached or suspected to be breached, the wallet must be regenerated and all funds relocated to a new wallet.
(b) All signatories must be separate background-checked individuals free of past criminal conviction. Canadians should have a right to know who holds their funds. All signing of transactions must take place with all signatories on Canadian soil or on the soil of a country with a solid legal system which agrees to uphold and support these rules (from an established white-list of countries which expands over time).
(c) 3-5 independent signatures are required for any withdrawal. There must be 1-3 spare signatories, and a maximum of 7 total signatories. The following are all valid combinations: 3of4, 3of5, 3of6, 4of5, 4of6, 4of7, 5of6, or 5of7.
(d) A security audit should be conducted to validate the cold wallet is set up correctly and provide any additional pertinent information. The primary purpose is to ensure that all signatories are acting independently and using best practices for private key storage. A report summarizing all steps taken and who did the audit will be made public. Canadians must be able to validate the right measures are in place to protect their funds.
(e) There is a simple approval process if signatories wish to visit any country outside Canada, with a potential whitelist of exempt countries. At most 2 signatories can be outside of aligned jurisdiction at any given time. All exchanges would be required to keep a compliant cold wallet for Canadian funds and have a Canadian office if they wish to serve Canadian customers.
(2) Regular and transparent solvency audits.
(a) An audit must be conducted at founding, after 3 months of operation, and at least once every 6 months to compare customer balances against all stored cryptocurrency and fiat balances. The auditor must be known, independent, and never the same twice in a row.
(b) An audit report will be published featuring the steps conducted in a readable format. This should be made available to all Canadians on the exchange website and on a government website. The report must include what percentage of each customer asset is backed on the exchange, and how those funds are stored.
(c) The auditor will independently produce a hash of each customer's identifying information and balance as they perform the audit. This will be made publicly available on the exchange and government website, along with simplified instructions that each customer can use to verify that their balance was included in the audit process.
(d) The audit needs to include a proof of ownership for any cryptocurrency wallets included. A satoshi test (spending a small amount) or partially signed transaction both qualify.
(e) Any platform without 100% reserves should be assessed on a regular basis by a government or industry watchdog. This entity should work to prevent any further drop, support any private investor to come in, or facilitate a merger so that 100% backing can be obtained as soon as possible.
(3) Protections for hot wallets and transactions.
(a) A standardized list of approved coins and procedures will be established to constitute valid cold storage wallets. Where a multi-sig process is not natively available, efforts will be undertaken to establish a suitable and stable smart contract standard. This list will be expanded and improved over time. Coins and procedures not on the list are considered hot wallets.
(b) Hot wallets can be backed by additional funds in cold storage or an acceptable third-party insurance provider with a comprehensive coverage policy.
(c) Exchanges are required to cover the full balance of all user funds as denominated in the same currency, or double the balance as denominated in bitcoin or CAD using an established trading rate. If the balance is ever insufficient due to market movements, the firm must rectify this within 24 hours by moving assets to cold storage or increasing insurance coverage.
(d) Any large transactions (above a set threshold) from cold storage to any new wallet addresses (not previously transacted with) must be tested with a smaller transaction first. Deposits of cryptocurrency must be limited to prevent economic 51% attacks. Any issues are to be covered by the exchange.
(e) Exchange platforms must provide suitable authentication for users, including making available approved forms of two-factor authentication. SMS-based authentication is not to be supported. Withdrawals must be blocked for 48 hours in the event of any account password change. Disputes on the negligence of exchanges should be governed by case law.

Steps Forward

Continued review of existing OSC feedback is still underway. More feedback and opinions on the framework and ideas as presented here are extremely valuable. The above is a draft and not finalized.
The process of further developing and bringing a suitable framework to protect Canadians will require the support of exchange operators, legal experts, and many others in the community. The costs of not doing such are tremendous. A large and convoluted framework, one based on flawed ideas or implementation, or one which fails to properly safeguard Canadians is not just extremely expensive and risky for all Canadians, severely limiting to the credibility and reputation of the industry, but an existential risk to many exchanges.
The responsibility falls to all of us to provide our insight and make our opinions heard on this critical matter. Please take the time to give your thoughts.
submitted by azoundria2 to QuadrigaInitiative [link] [comments]

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.
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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.
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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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Bitcoin 51% Attack - Clearly Explained

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