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Bob The Magic Custodian
Summary: Everyone knows that when you give your assets to someone else, they always keep them safe. If this is true for individuals, it is certainly true for businesses. Custodians always tell the truth and manage funds properly. They won't have any interest in taking the assets as an exchange operator would. Auditors tell the truth and can't be misled. That's because organizations that are regulated are incapable of lying and don't make mistakes. First, some background. Here is a summary of how custodians make us more secure: Previously, we might give Alice our crypto assets to hold. There were risks:
Alice might take the assets and disappear.
Alice might spend the assets and pretend that she still has them (fractional model).
Alice might store the assets insecurely and they'll get stolen.
Alice might give the assets to someone else by mistake or by force.
Alice might lose access to the assets.
But "no worries", Alice has a custodian named Bob. Bob is dressed in a nice suit. He knows some politicians. And he drives a Porsche. "So you have nothing to worry about!". And look at all the benefits we get:
Alice can't take the assets and disappear (unless she asks Bob or never gives them to Bob).
Alice can't spend the assets and pretend that she still has them. (Unless she didn't give them to Bob or asks him for them.)
Alice can't store the assets insecurely so they get stolen. (After all - she doesn't have any control over the withdrawal process from any of Bob's systems, right?)
Alice can't give the assets to someone else by mistake or by force. (Bob will stop her, right Bob?)
Alice can't lose access to the funds. (She'll always be present, sane, and remember all secrets, right?)
See - all problems are solved! All we have to worry about now is:
Bob might take the assets and disappear.
Bob might spend the assets and pretend that he still has them (fractional model).
Bob might store the assets insecurely and they'll get stolen.
Bob might give the assets to someone else by mistake or by force.
Bob might lose access to the assets.
It's pretty simple. Before we had to trust Alice. Now we only have to trust Alice, Bob, and all the ways in which they communicate. Just think of how much more secure we are! "On top of that", Bob assures us, "we're using a special wallet structure". Bob shows Alice a diagram. "We've broken the balance up and store it in lots of smaller wallets. That way", he assures her, "a thief can't take it all at once". And he points to a historic case where a large sum was taken "because it was stored in a single wallet... how stupid". "Very early on, we used to have all the crypto in one wallet", he said, "and then one Christmas a hacker came and took it all. We call him the Grinch. Now we individually wrap each crypto and stick it under a binary search tree. The Grinch has never been back since." "As well", Bob continues, "even if someone were to get in, we've got insurance. It covers all thefts and even coercion, collusion, and misplaced keys - only subject to the policy terms and conditions." And with that, he pulls out a phone-book sized contract and slams it on the desk with a thud. "Yep", he continues, "we're paying top dollar for one of the best policies in the country!" "Can I read it?' Alice asks. "Sure," Bob says, "just as soon as our legal team is done with it. They're almost through the first chapter." He pauses, then continues. "And can you believe that sales guy Mike? He has the same year Porsche as me. I mean, what are the odds?" "Do you use multi-sig?", Alice asks. "Absolutely!" Bob replies. "All our engineers are fully trained in multi-sig. Whenever we want to set up a new wallet, we generate 2 separate keys in an air-gapped process and store them in this proprietary system here. Look, it even requires the biometric signature from one of our team members to initiate any withdrawal." He demonstrates by pressing his thumb into the display. "We use a third-party cloud validation API to match the thumbprint and authorize each withdrawal. The keys are also backed up daily to an off-site third-party." "Wow that's really impressive," Alice says, "but what if we need access for a withdrawal outside of office hours?" "Well that's no issue", Bob says, "just send us an email, call, or text message and we always have someone on staff to help out. Just another part of our strong commitment to all our customers!" "What about Proof of Reserve?", Alice asks. "Of course", Bob replies, "though rather than publish any blockchain addresses or signed transaction, for privacy we just do a SHA256 refactoring of the inverse hash modulus for each UTXO nonce and combine the smart contract coefficient consensus in our hyperledger lightning node. But it's really simple to use." He pushes a button and a large green checkmark appears on a screen. "See - the algorithm ran through and reserves are proven." "Wow", Alice says, "you really know your stuff! And that is easy to use! What about fiat balances?" "Yeah, we have an auditor too", Bob replies, "Been using him for a long time so we have quite a strong relationship going! We have special books we give him every year and he's very efficient! Checks the fiat, crypto, and everything all at once!" "We used to have a nice offline multi-sig setup we've been using without issue for the past 5 years, but I think we'll move all our funds over to your facility," Alice says. "Awesome", Bob replies, "Thanks so much! This is perfect timing too - my Porsche got a dent on it this morning. We have the paperwork right over here." "Great!", Alice replies. And with that, Alice gets out her pen and Bob gets the contract. "Don't worry", he says, "you can take your crypto-assets back anytime you like - just subject to our cancellation policy. Our annual management fees are also super low and we don't adjust them often". How many holes have to exist for your funds to get stolen? Just one. Why are we taking a powerful offline multi-sig setup, widely used globally in hundreds of different/lacking regulatory environments with 0 breaches to date, and circumventing it by a demonstrably weak third party layer? And paying a great expense to do so? If you go through the list of breaches in the past 2 years to highly credible organizations, you go through the list of major corporate frauds (only the ones we know about), you go through the list of all the times platforms have lost funds, you go through the list of times and ways that people have lost their crypto from identity theft, hot wallet exploits, extortion, etc... and then you go through this custodian with a fine-tooth comb and truly believe they have value to add far beyond what you could, sticking your funds in a wallet (or set of wallets) they control exclusively is the absolute worst possible way to take advantage of that security. The best way to add security for crypto-assets is to make a stronger multi-sig. With one custodian, what you are doing is giving them your cryptocurrency and hoping they're honest, competent, and flawlessly secure. It's no different than storing it on a really secure exchange. Maybe the insurance will cover you. Didn't work for Bitpay in 2015. Didn't work for Yapizon in 2017. Insurance has never paid a claim in the entire history of cryptocurrency. But maybe you'll get lucky. Maybe your exact scenario will buck the trend and be what they're willing to cover. After the large deductible and hopefully without a long and expensive court battle. And you want to advertise this increase in risk, the lapse of judgement, an accident waiting to happen, as though it's some kind of benefit to customers ("Free institutional-grade storage for your digital assets.")? And then some people are writing to the OSC that custodians should be mandatory for all funds on every exchange platform? That this somehow will make Canadians as a whole more secure or better protected compared with standard air-gapped multi-sig? On what planet? Most of the problems in Canada stemmed from one thing - a lack of transparency. If Canadians had known what a joke Quadriga was - it wouldn't have grown to lose $400m from hard-working Canadians from coast to coast to coast. And Gerald Cotten would be in jail, not wherever he is now (at best, rotting peacefully). EZ-BTC and mister Dave Smilie would have been a tiny little scam to his friends, not a multi-million dollar fraud. Einstein would have got their act together or been shut down BEFORE losing millions and millions more in people's funds generously donated to criminals. MapleChange wouldn't have even been a thing. And maybe we'd know a little more about CoinTradeNewNote - like how much was lost in there. Almost all of the major losses with cryptocurrency exchanges involve deception with unbacked funds. So it's great to see transparency reports from BitBuy and ShakePay where someone independently verified the backing. The only thing we don't have is:
ANY CERTAINTY BALANCES WEREN'T EXCLUDED. Quadriga's largest account was $70m. 80% of funds are in 20% of accounts (Pareto principle). All it takes is excluding a few really large accounts - and nobody's the wiser. A fractional platform can easily pass any audit this way.
ANY VISIBILITY WHATSOEVER INTO THE CUSTODIANS. BitBuy put out their report before moving all the funds to their custodian and ShakePay apparently can't even tell us who the custodian is. That's pretty important considering that basically all of the funds are now stored there.
ANY IDEA ABOUT THE OTHER EXCHANGES. In order for this to be effective, it has to be the norm. It needs to be "unusual" not to know. If obscurity is the norm, then it's super easy for people like Gerald Cotten and Dave Smilie to blend right in.
It's not complicated to validate cryptocurrency assets. They need to exist, they need to be spendable, and they need to cover the total balances. There are plenty of credible people and firms across the country that have the capacity to reasonably perform this validation. Having more frequent checks by different, independent, parties who publish transparent reports is far more valuable than an annual check by a single "more credible/official" party who does the exact same basic checks and may or may not publish anything. Here's an example set of requirements that could be mandated:
First report within 1 month of launching, another within 3 months, and further reports at minimum every 6 months thereafter.
No auditor can be repeated within a 12 month period.
All reports must be public, identifying the auditor and the full methodology used.
All auditors must be independent of the firm being audited with no conflict of interest.
Reports must include the percentage of each asset backed, and how it's backed.
The auditor publishes a hash list, which lists a hash of each customer's information and balances that were included. Hash is one-way encryption so privacy is fully preserved. Every customer can use this to have 100% confidence they were included.
If we want more extensive requirements on audits, these should scale upward based on the total assets at risk on the platform, and whether the platform has loaned their assets out.
There are ways to structure audits such that neither crypto assets nor customer information are ever put at risk, and both can still be properly validated and publicly verifiable. There are also ways to structure audits such that they are completely reasonable for small platforms and don't inhibit innovation in any way. By making the process as reasonable as possible, we can completely eliminate any reason/excuse that an honest platform would have for not being audited. That is arguable far more important than any incremental improvement we might get from mandating "the best of the best" accountants. Right now we have nothing mandated and tons of Canadians using offshore exchanges with no oversight whatsoever. Transparency does not prove crypto assets are safe. CoinTradeNewNote, Flexcoin ($600k), and Canadian Bitcoins ($100k) are examples where crypto-assets were breached from platforms in Canada. All of them were online wallets and used no multi-sig as far as any records show. This is consistent with what we see globally - air-gapped multi-sig wallets have an impeccable record, while other schemes tend to suffer breach after breach. We don't actually know how much CoinTrader lost because there was no visibility. Rather than publishing details of what happened, the co-founder of CoinTrader silently moved on to found another platform - the "most trusted way to buy and sell crypto" - a site that has no information whatsoever (that I could find) on the storage practices and a FAQ advising that “[t]rading cryptocurrency is completely safe” and that having your own wallet is “entirely up to you! You can certainly keep cryptocurrency, or fiat, or both, on the app.” Doesn't sound like much was learned here, which is really sad to see. It's not that complicated or unreasonable to set up a proper hardware wallet. Multi-sig can be learned in a single course. Something the equivalent complexity of a driver's license test could prevent all the cold storage exploits we've seen to date - even globally. Platform operators have a key advantage in detecting and preventing fraud - they know their customers far better than any custodian ever would. The best job that custodians can do is to find high integrity individuals and train them to form even better wallet signatories. Rather than mandating that all platforms expose themselves to arbitrary third party risks, regulations should center around ensuring that all signatories are background-checked, properly trained, and using proper procedures. We also need to make sure that signatories are empowered with rights and responsibilities to reject and report fraud. They need to know that they can safely challenge and delay a transaction - even if it turns out they made a mistake. We need to have an environment where mistakes are brought to the surface and dealt with. Not one where firms and people feel the need to hide what happened. In addition to a knowledge-based test, an auditor can privately interview each signatory to make sure they're not in coercive situations, and we should make sure they can freely and anonymously report any issues without threat of retaliation. A proper multi-sig has each signature held by a separate person and is governed by policies and mutual decisions instead of a hierarchy. It includes at least one redundant signature. For best results, 3of4, 3of5, 3of6, 4of5, 4of6, 4of7, 5of6, or 5of7. History has demonstrated over and over again the risk of hot wallets even to highly credible organizations. Nonetheless, many platforms have hot wallets for convenience. While such losses are generally compensated by platforms without issue (for example Poloniex, Bitstamp, Bitfinex, Gatecoin, Coincheck, Bithumb, Zaif, CoinBene, Binance, Bitrue, Bitpoint, Upbit, VinDAX, and now KuCoin), the public tends to focus more on cases that didn't end well. Regardless of what systems are employed, there is always some level of risk. For that reason, most members of the public would prefer to see third party insurance. Rather than trying to convince third party profit-seekers to provide comprehensive insurance and then relying on an expensive and slow legal system to enforce against whatever legal loopholes they manage to find each and every time something goes wrong, insurance could be run through multiple exchange operators and regulators, with the shared interest of having a reputable industry, keeping costs down, and taking care of Canadians. For example, a 4 of 7 multi-sig insurance fund held between 5 independent exchange operators and 2 regulatory bodies. All Canadian exchanges could pay premiums at a set rate based on their needed coverage, with a higher price paid for hot wallet coverage (anything not an air-gapped multi-sig cold wallet). Such a model would be much cheaper to manage, offer better coverage, and be much more reliable to payout when needed. The kind of coverage you could have under this model is unheard of. You could even create something like the CDIC to protect Canadians who get their trading accounts hacked if they can sufficiently prove the loss is legitimate. In cases of fraud, gross negligence, or insolvency, the fund can be used to pay affected users directly (utilizing the last transparent balance report in the worst case), something which private insurance would never touch. While it's recommended to have official policies for coverage, a model where members vote would fully cover edge cases. (Could be similar to the Supreme Court where justices vote based on case law.) Such a model could fully protect all Canadians across all platforms. You can have a fiat coverage governed by legal agreements, and crypto-asset coverage governed by both multi-sig and legal agreements. It could be practical, affordable, and inclusive. Now, we are at a crossroads. We can happily give up our freedom, our innovation, and our money. We can pay hefty expenses to auditors, lawyers, and regulators year after year (and make no mistake - this cost will grow to many millions or even billions as the industry grows - and it will be borne by all Canadians on every platform because platforms are not going to eat up these costs at a loss). We can make it nearly impossible for any new platform to enter the marketplace, forcing Canadians to use the same stagnant platforms year after year. We can centralize and consolidate the entire industry into 2 or 3 big players and have everyone else fail (possibly to heavy losses of users of those platforms). And when a flawed security model doesn't work and gets breached, we can make it even more complicated with even more people in suits making big money doing the job that blockchain was supposed to do in the first place. We can build a system which is so intertwined and dependent on big government, traditional finance, and central bankers that it's future depends entirely on that of the fiat system, of fractional banking, and of government bail-outs. If we choose this path, as history has shown us over and over again, we can not go back, save for revolution. Our children and grandchildren will still be paying the consequences of what we decided today. Or, we can find solutions that work. We can maintain an open and innovative environment while making the adjustments we need to make to fully protect Canadian investors and cryptocurrency users, giving easy and affordable access to cryptocurrency for all Canadians on the platform of their choice, and creating an environment in which entrepreneurs and problem solvers can bring those solutions forward easily. None of the above precludes innovation in any way, or adds any unreasonable cost - and these three policies would demonstrably eliminate or resolve all 109 historic cases as studied here - that's every single case researched so far going back to 2011. It includes every loss that was studied so far not just in Canada but globally as well. Unfortunately, finding answers is the least challenging part. Far more challenging is to get platform operators and regulators to agree on anything. My last post got no response whatsoever, and while the OSC has told me they're happy for industry feedback, I believe my opinion alone is fairly meaningless. This takes the whole community working together to solve. So please let me know your thoughts. Please take the time to upvote and share this with people. Please - let's get this solved and not leave it up to other people to do. Facts/background/sources (skip if you like):
The inspiration for the paragraph about splitting wallets was an actual quote from a Canadian company providing custodial services in response to the OSC consultation paper: "We believe that it will be in the in best interests of investors to prohibit pooled crypto assets or ‘floats’. Most Platforms pool assets, citing reasons of practicality and expense. The recent hack of the world’s largest Platform – Binance – demonstrates the vulnerability of participants’ assets when such concessions are made. In this instance, the Platform’s entire hot wallet of Bitcoins, worth over $40 million, was stolen, facilitated in part by the pooling of client crypto assets." "the maintenance of participants (and Platform) crypto assets across multiple wallets distributes the related risk and responsibility of security - reducing the amount of insurance coverage required and making insurance coverage more readily obtainable". For the record, their reply also said nothing whatsoever about multi-sig or offline storage.
In addition to the fact that the $40m hack represented only one "hot wallet" of Binance, and they actually had the vast majority of assets in other wallets (including mostly cold wallets), multiple real cases have clearly demonstrated that risk is still present with multiple wallets. Bitfinex, VinDAX, Bithumb, Altsbit, BitPoint, Cryptopia, and just recently KuCoin all had multiple wallets breached all at the same time, and may represent a significantly larger impact on customers than the Binance breach which was fully covered by Binance. To represent that simply having multiple separate wallets under the same security scheme is a comprehensive way to reduce risk is just not true.
Private insurance has historically never covered a single loss in the cryptocurrency space (at least, not one that I was able to find), and there are notable cases where massive losses were not covered by insurance. Bitpay in 2015 and Yapizon in 2017 both had insurance policies that didn't pay out during the breach, even after a lengthly court process. The same insurance that ShakePay is presently using (and announced to much fanfare) was describe by their CEO himself as covering “physical theft of the media where the private keys are held,” which is something that has never historically happened. As was said with regard to the same policy in 2018 - “I don’t find it surprising that Lloyd’s is in this space,” said Johnson, adding that to his mind the challenge for everybody is figuring out how to structure these policies so that they are actually protective. “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.”
The most profitable policy for a private insurance company is one with the most expensive premiums that they never have to pay a claim on. They have no inherent incentive to take care of people who lost funds. It's "cheaper" to take the reputational hit and fight the claim in court. The more money at stake, the more the insurance provider is incentivized to avoid payout. They're not going to insure the assets unless they have reasonable certainty to make a profit by doing so, and they're not going to pay out a massive sum unless it's legally forced. Private insurance is always structured to be maximally profitable to the insurance provider.
The circumvention of multi-sig was a key factor in the massive Bitfinex hack of over $60m of bitcoin, which today still sits being slowly used and is worth over $3b. While Bitfinex used a qualified custodian Bitgo, which was and still is active and one of the industry leaders of custodians, and they set up 2 of 3 multi-sig wallets, the entire system was routed through Bitfinex, such that Bitfinex customers could initiate the withdrawals in a "hot" fashion. This feature was also a hit with the hacker. The multi-sig was fully circumvented.
Bitpay in 2015 was another example of a breach that stole 5,000 bitcoins. This happened not through the exploit of any system in Bitpay, but because the CEO of a company they worked with got their computer hacked and the hackers were able to request multiple bitcoin purchases, which Bitpay honoured because they came from the customer's computer legitimately. Impersonation is a very common tactic used by fraudsters, and methods get more extreme all the time.
A notable case in Canada was the Canadian Bitcoins exploit. Funds were stored on a server in a Rogers Data Center, and the attendee was successfully convinced to reboot the server "in safe mode" with a simple phone call, thus bypassing the extensive security and enabling the theft.
The very nature of custodians circumvents multi-sig. This is because custodians are not just having to secure the assets against some sort of physical breach but against any form of social engineering, modification of orders, fraudulent withdrawal attempts, etc... If the security practices of signatories in a multi-sig arrangement are such that the breach risk of one signatory is 1 in 100, the requirement of 3 independent signatures makes the risk of theft 1 in 1,000,000. Since hackers tend to exploit the weakest link, a comparable custodian has to make the entry and exit points of their platform 10,000 times more secure than one of those signatories to provide equivalent protection. And if the signatories beef up their security by only 10x, the risk is now 1 in 1,000,000,000. The custodian has to be 1,000,000 times more secure. The larger and more complex a system is, the more potential vulnerabilities exist in it, and the fewer people can understand how the system works when performing upgrades. Even if a system is completely secure today, one has to also consider how that system might evolve over time or work with different members.
By contrast, offline multi-signature solutions have an extremely solid record, and in the entire history of cryptocurrency exchange incidents which I've studied (listed here), there has only been one incident (796 exchange in 2015) involving an offline multi-signature wallet. It happened because the customer's bitcoin address was modified by hackers, and the amount that was stolen ($230k) was immediately covered by the exchange operators. Basically, the platform operators were tricked into sending a legitimate withdrawal request to the wrong address because hackers exploited their platform to change that address. Such an issue would not be prevented in any way by the use of a custodian, as that custodian has no oversight whatsoever to the exchange platform. It's practical for all exchange operators to test large withdrawal transactions as a general policy, regardless of what model is used, and general best practice is to diagnose and fix such an exploit as soon as it occurs.
False promises on the backing of funds played a huge role in the downfall of Quadriga, and it's been exposed over and over again (MyCoin, PlusToken, Bitsane, Bitmarket, EZBTC, IDAX). Even today, customers have extremely limited certainty on whether their funds in exchanges are actually being backed or how they're being backed. While this issue is not unique to cryptocurrency exchanges, the complexity of the technology and the lack of any regulation or standards makes problems more widespread, and there is no "central bank" to come to the rescue as in the 2008 financial crisis or during the great depression when "9,000 banks failed".
In addition to fraudulent operations, the industry is full of cases where operators have suffered breaches and not reported them. Most recently, Einstein was the largest case in Canada, where ongoing breaches and fraud were perpetrated against the platform for multiple years and nobody found out until the platform collapsed completely. While fraud and breaches suck to deal with, they suck even more when not dealt with. Lack of visibility played a role in the largest downfalls of Mt. Gox, Cryptsy, and Bitgrail. In some cases, platforms are alleged to have suffered a hack and keep operating without admitting it at all, such as CoinBene.
It surprises some to learn that a cryptographic solution has already existed since 2013, and gained widespread support in 2014 after Mt. Gox. Proof of Reserves is a full cryptographic proof that allows any customer using an exchange to have complete certainty that their crypto-assets are fully backed by the platform in real-time. This is accomplished by proving that assets exist on the blockchain, are spendable, and fully cover customer deposits. It does not prove safety of assets or backing of fiat assets.
If we didn't care about privacy at all, a platform could publish their wallet addresses, sign a partial transaction, and put the full list of customer information and balances out publicly. Customers can each check that they are on the list, that the balances are accurate, that the total adds up, and that it's backed and spendable on the blockchain. Platforms who exclude any customer take a risk because that customer can easily check and see they were excluded. So together with all customers checking, this forms a full proof of backing of all crypto assets.
However, obviously customers care about their private information being published. Therefore, a hash of the information can be provided instead. Hash is one-way encryption. The hash allows the customer to validate inclusion (by hashing their own known information), while anyone looking at the list of hashes cannot determine the private information of any other user. All other parts of the scheme remain fully intact. A model like this is in use on the exchange CoinFloor in the UK.
A Merkle tree can provide even greater privacy. Instead of a list of balances, the balances are arranged into a binary tree. A customer starts from their node, and works their way to the top of the tree. For example, they know they have 5 BTC, they plus 1 other customer hold 7 BTC, they plus 2-3 other customers hold 17 BTC, etc... until they reach the root where all the BTC are represented. Thus, there is no way to find the balances of other individual customers aside from one unidentified customer in this case.
Proposals such as this had the backing of leaders in the community including Nic Carter, Greg Maxwell, and Zak Wilcox. Substantial and significant effort started back in 2013, with massive popularity in 2014. But what became of that effort? Very little. Exchange operators continue to refuse to give visibility. Despite the fact this information can often be obtained through trivial blockchain analysis, no Canadian platform has ever provided any wallet addresses publicly. As described by the CEO of Newton "For us to implement some kind of realtime Proof of Reserves solution, which I'm not opposed to, it would have to ... Preserve our users' privacy, as well as our own. Some kind of zero-knowledge proof". Kraken describes here in more detail why they haven't implemented such a scheme. According to professor Eli Ben-Sasson, when he spoke with exchanges, none were interested in implementing Proof of Reserves.
And yet, Kraken's places their reasoning on a page called "Proof of Reserves". More recently, both BitBuy and ShakePay have released reports titled "Proof of Reserves and Security Audit". Both reports contain disclaimers against being audits. Both reports trust the customer list provided by the platform, leaving the open possibility that multiple large accounts could have been excluded from the process. Proof of Reserves is a blockchain validation where customers see the wallets on the blockchain. The report from Kraken is 5 years old, but they leave it described as though it was just done a few weeks ago. And look at what they expect customers to do for validation. When firms represent something being "Proof of Reserve" when it's not, this is like a farmer growing fruit with pesticides and selling it in a farmers market as organic produce - except that these are people's hard-earned life savings at risk here. Platforms are misrepresenting the level of visibility in place and deceiving the public by their misuse of this term. They haven't proven anything.
Fraud isn't a problem that is unique to cryptocurrency. Fraud happens all the time. Enron, WorldCom, Nortel, Bear Stearns, Wells Fargo, Moser Baer, Wirecard, Bre-X, and Nicola are just some of the cases where frauds became large enough to become a big deal (and there are so many countless others). These all happened on 100% reversible assets despite regulations being in place. In many of these cases, the problems happened due to the over-complexity of the financial instruments. For example, Enron had "complex financial statements [which] were confusing to shareholders and analysts", creating "off-balance-sheet vehicles, complex financing structures, and deals so bewildering that few people could understand them". In cryptocurrency, we are often combining complex financial products with complex technologies and verification processes. We are naïve if we think problems like this won't happen. It is awkward and uncomfortable for many people to admit that they don't know how something works. If we want "money of the people" to work, the solutions have to be simple enough that "the people" can understand them, not so confusing that financial professionals and technology experts struggle to use or understand them.
For those who question the extent to which an organization can fool their way into a security consultancy role, HB Gary should be a great example to look at. Prior to trying to out anonymous, HB Gary was being actively hired by multiple US government agencies and others in the private sector (with glowing testimonials). The published articles and hosted professional security conferences. One should also look at this list of data breaches from the past 2 years. Many of them are large corporations, government entities, and technology companies. These are the ones we know about. Undoubtedly, there are many more that we do not know about. If HB Gary hadn't been "outted" by anonymous, would we have known they were insecure? If the same breach had happened outside of the public spotlight, would it even have been reported? Or would HB Gary have just deleted the Twitter posts, brought their site back up, done a couple patches, and kept on operating as though nothing had happened?
In the case of Quadriga, the facts are clear. Despite past experience with platforms such as MapleChange in Canada and others around the world, no guidance or even the most basic of a framework was put in place by regulators. By not clarifying any sort of legal framework, regulators enabled a situation where a platform could be run by former criminal Mike Dhanini/Omar Patryn, and where funds could be held fully unchecked by one person. At the same time, the lack of regulation deterred legitimate entities from running competing platforms and Quadriga was granted a money services business license for multiple years of operation, which gave the firm the appearance of legitimacy. Regulators did little to protect Canadians despite Quadriga failing to file taxes from 2016 onward. The entire administrative team had resigned and this was public knowledge. Many people had suspicions of what was going on, including Ryan Mueller, who forwarded complaints to the authorities. These were ignored, giving Gerald Cotten the opportunity to escape without justice.
There are multiple issues with the SOC II model including the prohibitive cost (you have to find a third party accounting firm and the prices are not even listed publicly on any sites), the requirement of operating for a year (impossible for new platforms), and lack of any public visibility (SOC II are private reports that aren't shared outside the people in suits).
Securities frameworks are expensive. Sarbanes-Oxley is estimated to cost $5.1 million USD/yr for the average Fortune 500 company in the United States. Since "Fortune 500" represents the top 500 companies, that means well over $2.55 billion USD (~$3.4 billion CAD) is going to people in suits. Isn't the problem of trust and verification the exact problem that the blockchain is supposed to solve?
To use Quadriga as justification for why custodians or SOC II or other advanced schemes are needed for platforms is rather silly, when any framework or visibility at all, or even the most basic of storage policies, would have prevented the whole thing. It's just an embarrassment.
We are now seeing regulators take strong action. CoinSquare in Canada with multi-million dollar fines. BitMex from the US, criminal charges and arrests. OkEx, with full disregard of withdrawals and no communication. Who's next?
We have a unique window today where we can solve these problems, and not permanently destroy innovation with unreasonable expectations, but we need to act quickly. This is a unique historic time that will never come again.
Technical: A Brief History of Payment Channels: from Satoshi to Lightning Network
Who cares about political tweets from some random country's president when payment channels are a much more interesting and are actually capable of carrying value? So let's have a short history of various payment channel techs!
Generation 0: Satoshi's Broken nSequence Channels
Because Satoshi's Vision included payment channels, except his implementation sucked so hard we had to go fix it and added RBF as a by-product. Originally, the plan for nSequence was that mempools would replace any transaction spending certain inputs with another transaction spending the same inputs, but only if the nSequence field of the replacement was larger. Since 0xFFFFFFFF was the highest value that nSequence could get, this would mark a transaction as "final" and not replaceable on the mempool anymore. In fact, this "nSequence channel" I will describe is the reason why we have this weird rule about nLockTime and nSequence. nLockTime actually only works if nSequence is not 0xFFFFFFFF i.e. final. If nSequence is 0xFFFFFFFF then nLockTime is ignored, because this if the "final" version of the transaction. So what you'd do would be something like this:
You go to a bar and promise the bartender to pay by the time the bar closes. Because this is the Bitcoin universe, time is measured in blockheight, so the closing time of the bar is indicated as some future blockheight.
For your first drink, you'd make a transaction paying to the bartender for that drink, paying from some coins you have. The transaction has an nLockTime equal to the closing time of the bar, and a starting nSequence of 0. You hand over the transaction and the bartender hands you your drink.
For your succeeding drink, you'd remake the same transaction, adding the payment for that drink to the transaction output that goes to the bartender (so that output keeps getting larger, by the amount of payment), and having an nSequence that is one higher than the previous one.
Eventually you have to stop drinking. It comes down to one of two possibilities:
You drink until the bar closes. Since it is now the nLockTime indicated in the transaction, the bartender is able to broadcast the latest transaction and tells the bouncers to kick you out of the bar.
You wisely consider the state of your liver. So you re-sign the last transaction with a "final" nSequence of 0xFFFFFFFF i.e. the maximum possible value it can have. This allows the bartender to get his or her funds immediately (nLockTime is ignored if nSequence is 0xFFFFFFFF), so he or she tells the bouncers to let you out of the bar.
Now that of course is a payment channel. Individual payments (purchases of alcohol, so I guess buying coffee is not in scope for payment channels). Closing is done by creating a "final" transaction that is the sum of the individual payments. Sure there's no routing and channels are unidirectional and channels have a maximum lifetime but give Satoshi a break, he was also busy inventing Bitcoin at the time. Now if you noticed I called this kind of payment channel "broken". This is because the mempool rules are not consensus rules, and cannot be validated (nothing about the mempool can be validated onchain: I sigh every time somebody proposes "let's make block size dependent on mempool size", mempool state cannot be validated by onchain data). Fullnodes can't see all of the transactions you signed, and then validate that the final one with the maximum nSequence is the one that actually is used onchain. So you can do the below:
Become friends with Jihan Wu, because he owns >51% of the mining hashrate (he totally reorged Bitcoin to reverse the Binance hack right?).
Slip Jihan Wu some of the more interesting drinks you're ordering as an incentive to cooperate with you. So say you end up ordering 100 drinks, you split it with Jihan Wu and give him 50 of the drinks.
When the bar closes, Jihan Wu quickly calls his mining rig and tells them to mine the version of your transaction with nSequence 0. You know, that first one where you pay for only one drink.
Because fullnodes cannot validate nSequence, they'll accept even the nSequence=0 version and confirm it, immutably adding you paying for a single alcoholic drink to the blockchain.
The bartender, pissed at being cheated, takes out a shotgun from under the bar and shoots at you and Jihan Wu.
Jihan Wu uses his mystical chi powers (actually the combined exhaust from all of his mining rigs) to slow down the shotgun pellets, making them hit you as softly as petals drifting in the wind.
The bartender mutters some words, clothes ripping apart as he or she (hard to believe it could be a she but hey) turns into a bear, ready to maul you for cheating him or her of the payment for all the 100 drinks you ordered from him or her.
Steely-eyed, you stand in front of the bartender-turned-bear, daring him to touch you. You've watched Revenant, you know Leonardo di Caprio could survive a bear mauling, and if some posh actor can survive that, you know you can too. You make a pose. "Drunken troll logic attack!"
I think I got sidetracked here.
Bears are bad news.
You can't reasonably invoke "Satoshi's Vision" and simultaneously reject the Lightning Network because it's not onchain. Satoshi's Vision included a half-assed implementation of payment channels with nSequence, where the onchain transaction represented multiple logical payments, exactly what modern offchain techniques do (except modern offchain techniques actually work). nSequence (the field, but not its modern meaning) has been in Bitcoin since BitCoin For Windows Alpha 0.1.0. And its original intent was payment channels. You can't get nearer to Satoshi's Vision than being a field that Satoshi personally added to transactions on the very first public release of the BitCoin software, like srsly.
Miners can totally bypass mempool rules. In fact, the reason why nSequence has been repurposed to indicate "optional" replace-by-fee is because miners are already incentivized by the nSequence system to always follow replace-by-fee anyway. I mean, what do you think those drinks you passed to Jihan Wu are, other than the fee you pay him to mine a specific version of your transaction?
Satoshi made mistakes. The original design for nSequence is one of them. Today, we no longer use nSequence in this way. So diverging from Satoshi's original design is part and parcel of Bitcoin development, because over time, we learn new lessons that Satoshi never knew about. Satoshi was an important landmark in this technology. He will not be the last, or most important, that we will remember in the future: he will only be the first.
Incentive-compatible time-limited unidirectional channel; or, Satoshi's Vision, Fixed (if transaction malleability hadn't been a problem, that is). Now, we know the bartender will turn into a bear and maul you if you try to cheat the payment channel, and now that we've revealed you're good friends with Jihan Wu, the bartender will no longer accept a payment channel scheme that lets one you cooperate with a miner to cheat the bartender. Fortunately, Jeremy Spilman proposed a better way that would not let you cheat the bartender. First, you and the bartender perform this ritual:
You get some funds and create a transaction that pays to a 2-of-2 multisig between you and the bartender. You don't broadcast this yet: you just sign it and get its txid.
You create another transaction that spends the above transaction. This transaction (the "backoff") has an nLockTime equal to the closing time of the bar, plus one block. You sign it and give this backoff transaction (but not the above transaction) to the bartender.
The bartender signs the backoff and gives it back to you. It is now valid since it's spending a 2-of-2 of you and the bartender, and both of you have signed the backoff transaction.
Now you broadcast the first transaction onchain. You and the bartender wait for it to be deeply confirmed, then you can start ordering.
The above is probably vaguely familiar to LN users. It's the funding process of payment channels! The first transaction, the one that pays to a 2-of-2 multisig, is the funding transaction that backs the payment channel funds. So now you start ordering in this way:
For your first drink, you create a transaction spending the funding transaction output and sending the price of the drink to the bartender, with the rest returning to you.
You sign the transaction and pass it to the bartender, who serves your first drink.
For your succeeding drinks, you recreate the same transaction, adding the price of the new drink to the sum that goes to the bartender and reducing the money returned to you. You sign the transaction and give it to the bartender, who serves you your next drink.
At the end:
If the bar closing time is reached, the bartender signs the latest transaction, completing the needed 2-of-2 signatures and broadcasting this to the Bitcoin network. Since the backoff transaction is the closing time + 1, it can't get used at closing time.
If you decide you want to leave early because your liver is crying, you just tell the bartender to go ahead and close the channel (which the bartender can do at any time by just signing and broadcasting the latest transaction: the bartender won't do that because he or she is hoping you'll stay and drink more).
If you ended up just hanging around the bar and never ordering, then at closing time + 1 you broadcast the backoff transaction and get your funds back in full.
Now, even if you pass 50 drinks to Jihan Wu, you can't give him the first transaction (the one which pays for only one drink) and ask him to mine it: it's spending a 2-of-2 and the copy you have only contains your own signature. You need the bartender's signature to make it valid, but he or she sure as hell isn't going to cooperate in something that would lose him or her money, so a signature from the bartender validating old state where he or she gets paid less isn't going to happen. So, problem solved, right? Right? Okay, let's try it. So you get your funds, put them in a funding tx, get the backoff tx, confirm the funding tx... Once the funding transaction confirms deeply, the bartender laughs uproariously. He or she summons the bouncers, who surround you menacingly. "I'm refusing service to you," the bartender says. "Fine," you say. "I was leaving anyway;" You smirk. "I'll get back my money with the backoff transaction, and posting about your poor service on reddit so you get negative karma, so there!" "Not so fast," the bartender says. His or her voice chills your bones. It looks like your exploitation of the Satoshi nSequence payment channel is still fresh in his or her mind. "Look at the txid of the funding transaction that got confirmed." "What about it?" you ask nonchalantly, as you flip open your desktop computer and open a reputable blockchain explorer. What you see shocks you. "What the --- the txid is different! You--- you changed my signature?? But how? I put the only copy of my private key in a sealed envelope in a cast-iron box inside a safe buried in the Gobi desert protected by a clan of nomads who have dedicated their lives and their childrens' lives to keeping my private key safe in perpetuity!" "Didn't you know?" the bartender asks. "The components of the signature are just very large numbers. The sign of one of the signature components can be changed, from positive to negative, or negative to positive, and the signature will remain valid. Anyone can do that, even if they don't know the private key. But because Bitcoin includes the signatures in the transaction when it's generating the txid, this little change also changes the txid." He or she chuckles. "They say they'll fix it by separating the signatures from the transaction body. They're saying that these kinds of signature malleability won't affect transaction ids anymore after they do this, but I bet I can get my good friend Jihan Wu to delay this 'SepSig' plan for a good while yet. Friendly guy, this Jihan Wu, it turns out all I had to do was slip him 51 drinks and he was willing to mine a tx with the signature signs flipped." His or her grin widens. "I'm afraid your backoff transaction won't work anymore, since it spends a txid that is not existent and will never be confirmed. So here's the deal. You pay me 99% of the funds in the funding transaction, in exchange for me signing the transaction that spends with the txid that you see onchain. Refuse, and you lose 100% of the funds and every other HODLer, including me, benefits from the reduction in coin supply. Accept, and you get to keep 1%. I lose nothing if you refuse, so I won't care if you do, but consider the difference of getting zilch vs. getting 1% of your funds." His or her eyes glow. "GENUFLECT RIGHT NOW." Lesson learned?
Payback's a bitch.
Transaction malleability is a bitchier bitch. It's why we needed to fix the bug in SegWit. Sure, MtGox claimed they were attacked this way because someone kept messing with their transaction signatures and thus they lost track of where their funds went, but really, the bigger impetus for fixing transaction malleability was to support payment channels.
Yes, including the signatures in the hash that ultimately defines the txid was a mistake. Satoshi made a lot of those. So we're just reiterating the lesson "Satoshi was not an infinite being of infinite wisdom" here. Satoshi just gets a pass because of how awesome Bitcoin is.
CLTV-protected Spilman Channels
Using CLTV for the backoff branch. This variation is simply Spilman channels, but with the backoff transaction replaced with a backoff branch in the SCRIPT you pay to. It only became possible after OP_CHECKLOCKTIMEVERIFY (CLTV) was enabled in 2015. Now as we saw in the Spilman Channels discussion, transaction malleability means that any pre-signed offchain transaction can easily be invalidated by flipping the sign of the signature of the funding transaction while the funding transaction is not yet confirmed. This can be avoided by simply putting any special requirements into an explicit branch of the Bitcoin SCRIPT. Now, the backoff branch is supposed to create a maximum lifetime for the payment channel, and prior to the introduction of OP_CHECKLOCKTIMEVERIFY this could only be done by having a pre-signed nLockTime transaction. With CLTV, however, we can now make the branches explicit in the SCRIPT that the funding transaction pays to. Instead of paying to a 2-of-2 in order to set up the funding transaction, you pay to a SCRIPT which is basically "2-of-2, OR this singlesig after a specified lock time". With this, there is no backoff transaction that is pre-signed and which refers to a specific txid. Instead, you can create the backoff transaction later, using whatever txid the funding transaction ends up being confirmed under. Since the funding transaction is immutable once confirmed, it is no longer possible to change the txid afterwards.
Todd Micropayment Networks
The old hub-spoke model (that isn't how LN today actually works). One of the more direct predecessors of the Lightning Network was the hub-spoke model discussed by Peter Todd. In this model, instead of payers directly having channels to payees, payers and payees connect to a central hub server. This allows any payer to pay any payee, using the same channel for every payee on the hub. Similarly, this allows any payee to receive from any payer, using the same channel. Remember from the above Spilman example? When you open a channel to the bartender, you have to wait around for the funding tx to confirm. This will take an hour at best. Now consider that you have to make channels for everyone you want to pay to. That's not very scalable. So the Todd hub-spoke model has a central "clearing house" that transport money from payers to payees. The "Moonbeam" project takes this model. Of course, this reveals to the hub who the payer and payee are, and thus the hub can potentially censor transactions. Generally, though, it was considered that a hub would more efficiently censor by just not maintaining a channel with the payer or payee that it wants to censor (since the money it owned in the channel would just be locked uselessly if the hub won't process payments to/from the censored user). In any case, the ability of the central hub to monitor payments means that it can surveill the payer and payee, and then sell this private transactional data to third parties. This loss of privacy would be intolerable today. Peter Todd also proposed that there might be multiple hubs that could transport funds to each other on behalf of their users, providing somewhat better privacy. Another point of note is that at the time such networks were proposed, only unidirectional (Spilman) channels were available. Thus, while one could be a payer, or payee, you would have to use separate channels for your income versus for your spending. Worse, if you wanted to transfer money from your income channel to your spending channel, you had to close both and reshuffle the money between them, both onchain activities.
Poon-Dryja Lightning Network
Bidirectional two-participant channels. The Poon-Dryja channel mechanism has two important properties:
No time limit.
Both the original Satoshi and the two Spilman variants are unidirectional: there is a payer and a payee, and if the payee wants to do a refund, or wants to pay for a different service or product the payer is providing, then they can't use the same unidirectional channel. The Poon-Dryjam mechanism allows channels, however, to be bidirectional instead: you are not a payer or a payee on the channel, you can receive or send at any time as long as both you and the channel counterparty are online. Further, unlike either of the Spilman variants, there is no time limit for the lifetime of a channel. Instead, you can keep the channel open for as long as you want. Both properties, together, form a very powerful scaling property that I believe most people have not appreciated. With unidirectional channels, as mentioned before, if you both earn and spend over the same network of payment channels, you would have separate channels for earning and spending. You would then need to perform onchain operations to "reverse" the directions of your channels periodically. Secondly, since Spilman channels have a fixed lifetime, even if you never used either channel, you would have to periodically "refresh" it by closing it and reopening. With bidirectional, indefinite-lifetime channels, you may instead open some channels when you first begin managing your own money, then close them only after your lawyers have executed your last will and testament on how the money in your channels get divided up to your heirs: that's just two onchain transactions in your entire lifetime. That is the potentially very powerful scaling property that bidirectional, indefinite-lifetime channels allow. I won't discuss the transaction structure needed for Poon-Dryja bidirectional channels --- it's complicated and you can easily get explanations with cute graphics elsewhere. There is a weakness of Poon-Dryja that people tend to gloss over (because it was fixed very well by RustyReddit):
You have to store all the revocation keys of a channel. This implies you are storing 1 revocation key for every channel update, so if you perform millions of updates over your entire lifetime, you'd be storing several megabytes of keys, for only a single channel. RustyReddit fixed this by requiring that the revocation keys be generated from a "Seed" revocation key, and every key is just the application of SHA256 on that key, repeatedly. For example, suppose I tell you that my first revocation key is SHA256(SHA256(seed)). You can store that in O(1) space. Then for the next revocation, I tell you SHA256(seed). From SHA256(key), you yourself can compute SHA256(SHA256(seed)) (i.e. the previous revocation key). So you can remember just the most recent revocation key, and from there you'd be able to compute every previous revocation key. When you start a channel, you perform SHA256 on your seed for several million times, then use the result as the first revocation key, removing one layer of SHA256 for every revocation key you need to generate. RustyReddit not only came up with this, but also suggested an efficient O(log n) storage structure, the shachain, so that you can quickly look up any revocation key in the past in case of a breach. People no longer really talk about this O(n) revocation storage problem anymore because it was solved very very well by this mechanism.
Another thing I want to emphasize is that while the Lightning Network paper and many of the earlier presentations developed from the old Peter Todd hub-and-spoke model, the modern Lightning Network takes the logical conclusion of removing a strict separation between "hubs" and "spokes". Any node on the Lightning Network can very well work as a hub for any other node. Thus, while you might operate as "mostly a payer", "mostly a forwarding node", "mostly a payee", you still end up being at least partially a forwarding node ("hub") on the network, at least part of the time. This greatly reduces the problems of privacy inherent in having only a few hub nodes: forwarding nodes cannot get significantly useful data from the payments passing through them, because the distance between the payer and the payee can be so large that it would be likely that the ultimate payer and the ultimate payee could be anyone on the Lightning Network. Lessons learned?
We can decentralize if we try hard enough!
"Hubs bad" can be made "hubs good" if everybody is a hub.
Smart people can solve problems. It's kinda why they're smart.
After LN, there's also the Decker-Wattenhofer Duplex Micropayment Channels (DMC). This post is long enough as-is, LOL. But for now, it uses a novel "decrementing nSequence channel", using the new relative-timelock semantics of nSequence (not the broken one originally by Satoshi). It actually uses multiple such "decrementing nSequence" constructs, terminating in a pair of Spilman channels, one in both directions (thus "duplex"). Maybe I'll discuss it some other time. The realization that channel constructions could actually hold more channel constructions inside them (the way the Decker-Wattenhofer puts a pair of Spilman channels inside a series of "decrementing nSequence channels") lead to the further thought behind Burchert-Decker-Wattenhofer channel factories. Basically, you could host multiple two-participant channel constructs inside a larger multiparticipant "channel" construct (i.e. host multiple channels inside a factory). Further, we have the Decker-Russell-Osuntokun or "eltoo" construction. I'd argue that this is "nSequence done right". I'll write more about this later, because this post is long enough. Lessons learned?
Bitcoin offchain scaling is more powerful than you ever thought.
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