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How Mimblewimble Could Make Bitcoin Work Better

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Bitcoin

Mimblewimble claims to use a new cryptographic protocol that could revolutionize the way bitcoin works, making it more scalable and private.

The protocol generates a blinding factor that can prove ownership of bitcoins, making private keys unnecessary, and offering a solution to the need to balance bitcoin privacy against fungibility while also improving scalability, according to a white paper that appeared mysteriously on a bitcoin research site authored by a person using a pseudonym.

The author refers to himself as “Tom Elvis Jedusor,” a name taken from the Harry Potter novels.

Bitcoin’s Verification Challenge

Verification

Bitcoin is the first widely used financial system for which all the necessary data to validate the system status can be cryptographically verified by anyone, the white paper notes.

It accomplishes this by storing all transactions in a public database called “the blockchain.” Someone who wants to check this state has to download the whole chain and replay each transaction, checking each one as they go.

It would be easier if an auditor only had to check data on the outputs themselves, but this is not possible since they are only valid if the output is at the end of a chain of prior outputs. The whole blockchain has to be validated to confirm the final state.

Considering that the transactions are cryptographically atomic, the outputs that go into and emerge from every transaction are very clear. The “transaction graph” that results reveals a lot of information and is subjected to analysis by numerous companies whose business model is to monitor and control the lower classes.

This makes it very non-private and even dangerous to use.

Proposed Solutions

Some solutions to this have been proposed, Jedusor notes. Greg Maxwell discovered how to encrypt the amounts so that the graph of the transaction is faceless but still validates the sums. Maxwell also produced CoinJoin, a system for bitcoin users to combine interactively transactions, confusing the transaction graph.

Nicolas van Saberhagen developed a system to blind the transaction entries, further clouding the transaction graph. Shen Noether combined the two approaches to obtain the “confidential transactions” of Maxwell and the “darkening” of van Saberhagen.

These solutions would make bitcoin safe, Jedusor observes. But too much data can make things worse. Confidential transactions require multi-kilobyte proofs on every output. van Saberhagen signatures require every output to be stored forever, as it is not possible to truly tell when they are spent.

Maxwell’s CoinJoin needs interactivity. Yuan Horas Mouton fixed this by making transactions freely mergeable, but he had to use pairing-based cryptography which can be slower and harder to trust. He called this “one-way aggregate signatures” (OWAS).

OWAS combined the transactions in blocks. It could be possible to combine across blocks (perhaps with some glue data) so that when the outputs are created and destroyed, it is as if they never existed, Jedusor notes.

Then, to validate the entire chain, users only need to know when money enters the system (new money in each block as in bitcoin or Monero or peg-ins for sidechains) and final unspent outputs. The rest can be removed and forgotten.

Confidential transactions hide the amounts and OWAS to blur the transaction graph by using less space than bitcoin to enable users to verify the blockchain.

Mimblewimble prevents the blockchain from referencing all of a user’s information, Jedusor observes.

Confidential Transactions

The first step is to remove bitcoin Script. It is too powerful, so it is impossible to merge transactions using general scripts.

Instant transaction

Maxwell’s Confidential Transactions are enough (after some small modification) to authorize the spending of outputs and also to make combined transactions without interaction. This is identical to OWAS, enabling the relaying nodes to take some transaction fee or the recipient to change the transaction fee. Bitcoin cannot do these additional things.

In Confidential Transactions work, the amounts are coded by the following equation: C = r*G + v*H.

C is a Pedersen commitment, G and H are fixed nothing-up-my-sleeve elliptic curve group generators, v is the amount, and r is a secret random blinding key.

Attached to this output is a rangeproof proving that v is in [0, 2^64], so the user cannot exploit the blinding to produce overflow attacks, etc.

To validate a transaction, the verifier will add commitments for all outputs, plus f*H (f being the transaction fee that is given explicitly) and subtracts all input commitments. The result must be 0, proving no amount was created or destroyed overall.

To create such a transaction, the user has to know the sum of the values of r for commitments entries. Therefore, r-values (and their sums) serve as secret keys. If the r output values are made known only to the recipient, an authentication system exists. Unfortunately, by keeping the rule that commits all to add up to zer0, this is impossible since the sender knows the sum of all his r values, and therefore knows the recipient’s r values sum to the negative of that.

Instead, the transaction is allowed to sum to a non-zero value,  k*G, and require a signature of an empty string with this as key, proving its amount component is zero.

The transactions can have as many k*G values as they want, each with a signature, and sum them up during verification.

Creating Transactions

To create transactions, the sender and recipient do the following:

1) The sender and recipient agree on the amount to send. Call this b.

2) The sender creates a transaction with all inputs and change output(s), and gives the recipient the total blinding factor (r-value of change minus r-values of inputs) along with the transaction. The commitments sum to r*G – b*H.

3) The recipient chooses random r-values for his outputs, and values that sum to b minus fee, then adds these to the transaction (including range proof). Now the commitments sum to k*G – fee*H for some k that only the recipient knows.

4) The recipient attaches the signature with k to the transaction, and the explicit fee.

Creating transactions like this supports OWAS already. To demonstrate this, consider two transactions that have a surplus k1*G and k2*G, and the attached signatures with these. Then combine the lists of inputs and outputs of the two transactions, with both k1*G and k2*G to the mix, and it is again a valid transaction. From the combination, it is not possible to know which outputs or inputs are from which original transaction.

Because of this, the block format changes from bitcoin to this information:

1) Explicit amounts for new money (block subsidy or sidechain peg-ins) with whatever else data this needs. For a sidechain peg-in, it may reference a bitcoin transaction that commits to a specific excess k*G value.

2) Inputs of all transactions.

3) Outputs of all transactions.

4) Excess k*G values for all transactions.

Each is grouped together because it does not matter what the transaction boundaries are originally. In addition, lists 2, 3 and 4 should be coded in alphabetical order, since it is quick to check and prevents the block creator from leaking any information about the original transactions.

The outputs are now identified by their hash, rather than their position in a transaction that could easily change. Therefore, it should be banned to have two unspent outputs equal at the same time to avoid confusion.

Merging Transactions

Maxwell’s Confidential Transactions has already been used to create a non-interactive version of his CoinJoin. Another idea is needed. A non-interactive version of this is created to show how it is used with several blocks.

Each block can be seen as one large transaction. To validate it, add the output commitments together, then subtract the input commitments, k*G values, and the explicit input amounts times H. The transactions from two blocks can be combined to form a single block, resulting again in a valid transaction.

The difference is that output commitments have an input commitment equal to it, where the first block’s output is spent in the second block. Both commitments can be removed and still have a valid transaction. There is not even the need to check the rangeproof of the deleted output.

The extension of this idea, all the way from the genesis block to the latest block, shows that each non-explicit input is deleted with its referenced output. All that remains are the unspent outputs, explicit input amounts and every k*G value.

The entire mess can be validated as if it were one transaction by adding all unspent commitments output, subtracting the values k*G, validating explicit input amounts (if there is anything to validate) and subtracting them times H. If the sum is zero, the complete chain is good.

When a user downloads the chain, the following data is needed from each block:

1) Explicit amounts for new money (block subsidy or sidechain peg-ins) with whatever else data this needs.

2) Unspent outputs of all transactions, along with a merkle proof that each output appeared in the original block.

3) Excess k*G values for all transactions.

Bitcoin currently has about 423000 blocks, totaling around 80GB of data on the hard drive to validate everything. The data represents around 150 million transactions and 5 million
unspent, non-confidential outputs.

Each unspent output on a Mimblewimble chain is around 3Kb for rangeproof and Merkle proof. Each transaction adds around 100 bytes: a k*G value and a signature.

The block headers and explicit amounts are negligible. Added together this is 30Gb – with an obscured transaction graph and a confidential transaction.

Also read: Mimblewimble: A stripped down version of bitcoin improves privacy, fungibility and scalability 

Questions and Intuition

The following questions arise.

Q: If you delete the transaction outputs, the user cannot verify the rangeproof and may be a negative amount is created.

A: This is acceptable. For the entire transaction to validate, all negative amounts must have been destroyed. Users have SPV security only that no illegal inflation happened in the past, but the user knows that at this time, no inflation occurred.

Q: If you delete the inputs, double spending can happen.

A: In fact, this means someone may claim that unspent output was spent in the old days. But this is impossible, otherwise the sum of the combined transaction could not be zero.

An exception is that if the outputs amount to zero, it is possible to make two that are negatives of each other, and the pair can be revived without anything that breaks. So to prevent consensus problems, outputs 0-amount should be banned. Just add H at each output.

They all amount to at least 1 at present.

Future Research

Here are some questions that cannot be answered at the time of this writing.

1) What script support is possible? One would need to translate script operations into some discrete logarithm information.

2) Users are required to check all k*G values when in fact all that is needed is that the sum is of the form k*G. Instead of using signatures, is there another proof of discrete logarithm that could be combined?

3) There is a denial-of-service option when a user downloads the chain. The peer can give gigabytes of data and list the wrong unspent outputs. The user will see that the results do not add up to 0, but cannot tell where the problem is.

For now, maybe the user should just download the blockchain from a Torrent or something where the data is shared between many users and is reasonably likely to be correct.

Images from Shutterstock.

Important: Never invest (trade with) money you can't afford to comfortably lose. Always do your own research and due diligence before placing a trade. Read our Terms & Conditions here. Trade recommendations and analysis are written by our analysts which might have different opinions. Read my 6 Golden Steps to Financial Freedom here. Best regards, Jonas Borchgrevink.

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3.9 stars on average, based on 8 rated postsLester Coleman is a veteran business journalist based in the United States. He has covered the payments industry for several years and is available for writing assignments.




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  1. Ade

    September 4, 2016 at 11:25 pm

    Is that you Dr Satoshi ?

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Altcoins

Cryptocurrency Prices Have Recovered $26 Billion from Last Week’s Bear-Market Low

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Cryptocurrency prices were seeing green on Tuesday, as investors continued to rally behind news of a popular bitcoin trading app being granted regulatory approval to operate in New York. The push for regulated crypto custodial services has also not gone unnoticed, with the likes of Coinbase looking to overcome one of the final barriers to institutional adoption.

Crypto Prices Hit One-Week High

Digital currencies on Tuesday overcame tepid trading conditions and lower trade volumes to reach their highest level in seven days. The total market peaked at $294.2 billion at 17:00 UTC but has since consolidated at $290.5 billion, according to CoinMarketCap. As a reminder, the market bottomed near $264 billion last week, the lowest since early April.

Crypto prices have been surprisingly stable since last week’s brisk selloff. As Hacked reported earlier, bitcoin volatility is at its lowest level in a year even while factoring the latest price collapse.

Almost all of the top-ten coins had reported gains over the past 24 hours. Tron’s 8.3% gain was the biggest, with TRX trading at $0.048.

Ethereum rose 3.4% over the past 24 hours to trade at $536.86. Bitcoin cash reported slight gains, climbing 1.6% to $900.54.

Bitcoin was virtually unchanged compared with the same time Monday. The world’s largest cryptocurrency by market cap is up 2.5% over the past seven days.

Although trading volumes were a paltry $13.2 billion, turnover is up 39% from Sunday’s lows.

Prices received their initial boost Monday afternoon on news that Square, Inc.’s Cash app was granted a BitLicense to operate in New York. The app, which has a bitcoin trading platform, has more than seven million active users. The company, which is led by Twitter’s Jack Dorsey, saw its share price and market cap rise significantly on the news.

Custodianship: The Final Frontier?

San Francisco-based Coinbase has joined forces with hedge funds and third-party custodians to unlock up to $10 billion in institutional capital. According to some industry insiders, custodianship is the last of the major barriers to widespread cryptocurrency adoption among hedge funds, banks and day traders.

As Goldman Sachs, Nomura Holdings and others have demonstrated, there is strong appetite for cryptocurrencies at the institutional level. But without a stable and robust custodian service, staking large positions on a highly volatile market is not considered feasible. This is especially the case for funds that are involved with handling university endowments and pension programs.

According to Ari Paul, co-founder of the Blocktower crypto-focused hedge fund, institutional money has been trickling into the digital currency market since mid-2017. And while adoption has been slower than expected, “that doesn’t mean it’s not coming,” Paul tweeted May 31. “There are a lot of pieces that need to come together, one big piece being third party custody,” he said.

Kyle Samani, a cryptocurrency hedge fund manager, recently told Bloomberg that custodianship is viewed as “the final barrier” to market entry. “Over the next year, the market will come to recognize that custodianship is a solved problem. This will unlock a big wave of capital,” he said.

Disclaimer: The author owns bitcoin, Ethereum and other cryptocurrencies. He holds investment positions in the coins, but does not engage in short-term or day-trading.

Featured image courtesy of Shutterstock.

Important: Never invest (trade with) money you can't afford to comfortably lose. Always do your own research and due diligence before placing a trade. Read our Terms & Conditions here. Trade recommendations and analysis are written by our analysts which might have different opinions. Read my 6 Golden Steps to Financial Freedom here. Best regards, Jonas Borchgrevink.

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4.5 stars on average, based on 457 rated postsSam Bourgi is Chief Editor to Hacked.com, where he specializes in cryptocurrency, economics and the broader financial markets. Sam has nearly eight years of progressive experience as an analyst, writer and financial market commentator where he has contributed to the world's foremost newscasts.




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Bitcoin

China and the Next Cryptocurrency Bull Market 

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Cryptocurrency experts from mainland China believe we are on the cusp of another bull market for digital currency. And it could be nationals from their own country who help drive the “fifth wave” of the market uptrend.

Chinese Investors Will Drive Next Crypto Bull Market, Experts Predict

In a recent interview with Tencent Technology, Sun Zeyu of Genesis Capital said cryptocurrencies are poised to continue higher in the fourth quarter as investors shake off the sentiment-laden collapses of the first six months of 2018.

Gensis Capital is a Hong Kong-based investment firm specializing in growth-stage internet companies.

Gao Kangdi of Metropolis VC told Chinese media that “the scale of the fifth wave of the crypto bull market may be far beyond our imagination.”

What these industry voices have in common is the belief that China will play a major role in the next bull market in spite of a nation-wide ban on the trading and mining of digital assets. They cite massive flows of capital already into the blockchain and crypto ecosystem already underway in places like Singapore.

The tiny city-state is now home to thousands of foundations established by Chinese nationals. This has been corroborated by Chen Xianhui, a local agent helping Chinese nationals set up foundations in Singapore. According to Chen, most of these thousand-plus foundations are token investments funds.

Setting up a foundation in Singapore costs only 10,000 RMB ($1,561 U.S.) and takes just 15 days.

Singapore has emerged as one of the more favorable destinations for initial coin offerings (ICOs) and other market players. The Monetary Authority of Singapore (MAS) last month proposed changes to its current regulatory regime that will make it easier for blockchain-related exchanges to set up shop n the country.

Instability in Traditional Markets

China’s crypto analysts believe global financial instability and the growing threat of risk aversion could play into the hands of digital currencies. Bitcoin is often posited as a non-correlated asset, which means it moves independently of the broader financial market. Although some observers noted a small correlation between bitcoin and stocks earlier this year, this was largely due to the influx of new crypto traders to the market.

While it’s far too premature to call for a bear market in global equities, a sharp rise in bond yields and growing instability in emerging-market currencies have been the source of significant tumult in recent months. The next critical test for equities will be the gradual winding down of crisis-era policies.

The European Central Bank (ECB) announced Thursday it would put an end to its record bond-buying program this year. Meanwhile, the U.S. Federal Reserve is planning to raise interest rates two more times for 2018.

Bitcoin’s status as a safe haven has been contested by those who argue that virtual currencies have no intrinsic value. However, analysts at Goldman Sachs believe the opposite is true as assets like bitcoin continue to grow and mature.

In particular, Goldman Sachs analyst Zach Pandl has argued that bitcoin will follow a similar trajectory as gold in the long run as a low-return, hedge-like asset.

“We should stress that, as money, cryptocurrencies should have low expected returns in the long run, despite their high returns recently,” he wrote back in January. “Digital currencies should be thought of as low/zero return or hedge-like assets, akin to gold or certain other metals.”

Charles Thorngren, CEO of Noble Alternative Investments, believes bitcoin is also attracting a new type of investor: namely, equity investors who are looking for new options.

In an interview with Forbes, Thorngren said the following:

“The base of bitcoin has changed, in fact it has evolved, to a wider base of investors. People who have only invested in equities are now looking for options as the rumblings in the stock and bond market increase.

This new investor helps to establish a stronger Bitcoin market and adds legitimacy to the Cryptocurrencies as a whole.”

Disclaimer: The author owns bitcoin, Ethereum and other cryptocurrencies. He holds investment positions in the coins, but does not engage in short-term or day-trading.

Featured image courtesy of Shutterstock.

Important: Never invest (trade with) money you can't afford to comfortably lose. Always do your own research and due diligence before placing a trade. Read our Terms & Conditions here. Trade recommendations and analysis are written by our analysts which might have different opinions. Read my 6 Golden Steps to Financial Freedom here. Best regards, Jonas Borchgrevink.

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4.5 stars on average, based on 457 rated postsSam Bourgi is Chief Editor to Hacked.com, where he specializes in cryptocurrency, economics and the broader financial markets. Sam has nearly eight years of progressive experience as an analyst, writer and financial market commentator where he has contributed to the world's foremost newscasts.




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Analysis

Crypto Update: Coins Pop Higher as Consolidation Continues

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Trading activity increased in the major coins today, amid a mixed news flow, and for now, bulls scored a small victory following last week’s bearish price action. Bitcoin, Ethereum and most of the largest digital currencies gained several percents, despite the weekend’s deterioration, and although the technical setup didn’t change significantly, an immediate breakdown has been averted.

The discouraging BIS report that has been making waves today wasn’t enough to push the coins below support, but for now, the short-term strength left the trading range intact with the primary resistance levels still keeping a lid on prices. Given the uncertain long-term picture, the coming weeks will be crucial for the largest coins and the whole segment alike, with Bitcoin being in the center of attention after its long period of relative weakness.

BTC/USD, 4-Hour Chart Analysis

Bitcoin held up above the April low, despite the bearish short-term picture, and the coin the highest price level in a week, breaching the $6750 level in the process. While the most valuable coin fared relatively well today, it clearly remains a laggard from a broader perspective, and it is still trading in a declining short-term trend, with several strong resistance levels just ahead.

The $5850 is the key from a long-term perspective, with further support levels at $6500 and $6275 and resistance ahead at $7000 and $7350.

Bearish Rotation Among Altcoins

ETH/USD, 4-Hour Chart Analysis

On a negative note, the leaders of the latest rally were among the weaker coins today, and that is a sign of bearish rotation in a segment, and until major resistance levels are broken traders shouldn’t enter new positions here. Ethereum managed to rally above $500 yet again, but it remained below week’s bounce high, leaving the trading range intact, while the declining short-term trend is also still dominant.  Strong resistance is still ahead between $555 and $575, while support below $500 is found at $450, $400, and $380.

EOS/USD, 4-Hour Chart Analysis

EOS, which is one of the strongest majors technically speaking also edged higher today, but it remains stuck in the declining short-term pattern, and below key support/resistance zone near $12. The coin is well below last week’s high and until a confirmed short-term trend change, traders shouldn’t enter positions here.

Featured image from Shutterstock

Disclaimer:  The analyst owns cryptocurrencies. He holds investment positions in the coins, but doesn’t engage in short-term or day-trading, nor does he hold short positions on any of the coins.

Important: Never invest (trade with) money you can't afford to comfortably lose. Always do your own research and due diligence before placing a trade. Read our Terms & Conditions here. Trade recommendations and analysis are written by our analysts which might have different opinions. Read my 6 Golden Steps to Financial Freedom here. Best regards, Jonas Borchgrevink.

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4.6 stars on average, based on 277 rated postsTrader and financial analyst, with 10 years of experience in the field. An expert in technical analysis and risk management, but also an avid practitioner of value investment and passive strategies, with a passion towards anything that is connected to the market.




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