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Our email list is divided into three categories: regions, industries and job functions. Regional email can help businesses target consumers or businesses in specific areas. Sample Email Lists broken down by industry help optimize your advertising efforts. If you’re marketing to a niche buyer, then our email lists filtered by job function can be incredibly helpful.

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Another problem could be that a seller having been honest up until now but no longer has an incentive to be honest if they wish to leave the market (say that their sales are declining). In this case, their motivation is to systematically cheat customers at once, and then get out of the market. Thus, reputation isn’t a good thing at the start or the end of a seller’s involvement on the market. Sample Email  id list

A reputation-based strategy is also not a good idea when consumers do not have a habit of doing transactions with the same company or when the product line is new and there’s not sufficient time to establish an image. A highly-tech market such as Bitcoin exchanges is prone to these issues. Sample Email address lists

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The third market-based option is to provide warranties. The concept is that a seller can offer a guarantee to the purchaser that states in the event that the widget proves to be of poor quality and the seller offers an exchange or refund. This can be a good idea until a certain point, but there’s another issue in that a warranty is another type of product that could also come in premium or low-quality models! A low-quality warranty is that doesn’t perform when you get back the defective product. They do not honor their word or force you to jump through a variety of hurdles.

Regulative fixes.So in the event that a lemons market has been created, and these market-based methods do not work in the specific marketplace, regulation may aid. In particular there are three ways that regulation could be able to solve the issue. Sample Email  database providers

In the first place, regulations could make disclosure mandatory. It could mandate, for instance that all widgets be classified as high or low quality, and paired with penalties for companies for making false claims. This gives consumers the information that they are lacking. Another way to regulate is to establish high standards of quality, which ensure that no widget can sell unless it has a certain quality test standard and that standard is established so that only top-quality widgets will be able to pass the test. This would create an industry that has only one type of widget, however at least the widgets are of high quality with the expectation that the regulations work in the way it was intended. The third option is to require sellers to provide warranties in order to enforce the validity of those warranties , so that sellers have to keep the commitments they make. Sample email lists
Any of these methods of regulation can fail , and it could not function as planned and could also be

Incorrectly written or applied, it could be burdensome for sellers. There is at least the possibility that regulation of this kind could help address the problems with market functioning due to the lemons market. Some who argue for the regulatory oversight for Bitcoin exchanges, like frequently cite Bitcoin exchanges as an instance of a lemons market.

Collaboration and Antitrust law.Another reason why markets aren’t functioning as we would prefer can be price fixation. Price fixing occurs the case when sellers collide with one another and agree to increase prices or not lower the prices. Similar situations occur when companies that are otherwise into competition decide not to compete. For instance, if were two bakeries operating in the town, they could agree that one will only sell muffins , and the other one will only offer bagels. That way there’s less competition that there would be they sold muffins as well as bagels. Due to the less competition, prices rise, and the sellers are able to thwart the workings in the marketplace.

In the end, the reason the market safeguards consumers in its regular functioning is because of the mechanism of competition. Sellers need to compete to ensure that they can offer the highest quality products at the lowest price to the consumer If they do not be competitive in this way, they’ll not get any business. A contract for fixing price or not compete thwarts competition. If people make decisions to prevent competition, it’s another type of market failure. Sample Email  database providers

These agreements that seek to increase prices or to avoid competition is illegal in the majority of areas. It is a part of the antitrust law or law on competition. The aim of this law is to stop intentional actions that hinder or hurt competition. In general, it restricts the scope of actions beyond providing high-quality products at reasonable costs, like attempts to decrease competition via mergers. Antitrust law is a complex area and we’ve only provided a an outline of it however it’s a further example of the way that markets can fail, and how the law could and will assist in stopping it.

New York’s BitLicense Proposal Sample email lists

In the past, we’ve talked about the topic of regulation in general, including different kinds of regulations, the reasons how regulation can be justified in certain situations and also make economic sense. Let’s now look at an effort made by an individual state to bring in specific rules for Bitcoin specifically, NY State’s BitLicense proposal. This information is up-to-date at the time of writing, however the landscape of Bitcoin regulation can change rapidly. This isn’t a big deal in our case, as our objective isn’t to assist you in understanding an individual piece of regulations or proposals. Instead, we’re trying to let you know the types of things that regulators are up to and provide you with a glimpse of how they approach the issue. buy Sample Email  database

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The BitLicense proposal was released in July 2014, and since then has been updated in response to feedback by the Bitcoin community, the industry as well as the general public and various other participants. The proposal was released from the New York State Department of Financial Services which is the department that is part of the State of New York that regulates the financial sector. Of course this state New York has the world’s largest financial hub, consequently, it’s a part the state government and has the ability to handle the largest of organizations. Sample Email  id list

Who’s covered.BitLicense is an unproposed set of rules, codes and regulations something to do the use of virtual currency. It basically states that you’ll need an item known as an BitLicense by contacting the New York Department of Financial Services If you want to carry out one of the activities that are listed below: Sample Email  database providers

Virtual Currency Businesses refers to the execution of any of the following actions that involve New York or a New York resident:

1. Receiving Virtual Currency to transmit or transfer Virtual Currency with the exception that the transaction is for non-financial reasons and does not require transfers of greater than minimal value of the Virtual Currency;

2. 3. or ensuring custody or control of virtual Currency on behalf of other people;

3. Selling and buying virtual Currency as a service for customers; Sample email lists

4. performing Exchange Services as an enterprise that is a customer; buy Sample Email database online

5. Controlling, administering or distributing the administration, control, or issue of a Virtual Currency.

The creation and distribution of software on its own is not a Virtual Currency Business Activity.

The text speaks of “activities involving New York or a New York Resident,” indicating the authority of regulation of NYDFS. However, the consequences of rules like these extend far beyond the boundaries of the state for two reasons. First, for states that have large populations, like New York or California, when faced with the option of adhering to state laws or not conducting business with consumers in those states, the majority of businesses opt to adhere. Furthermore, certain states are generally regarded as authorities in certain economic areas, such as finance for New York, technology in the case of California. This implies that the other U.S. states often follow the same direction they choose to established.

Take note of the exemption to non-financial applications in the first sectionThis was added in the 2nd revision and it’s an excellent one. It’s a carve-out for just the kind of Bitcoin-as-a-platform applications that we’ll look at starting in Chapter 9. The second one could cover aspects such as services for wallets. For the third category it is believed that you are able to purchase and sell bitcoins on your own however doing this as a business for customers requires an BitLicense. The fourth category is easy to understand. The last one could apply to altcoins, a lot of which are a bit centralized, as opposed to Bitcoin. We’ll discuss altcoins in Chapter 10.

The software development exception at the end of the article is significant. The language was not in the initial version and caused protests in the public. NYDFS Superintendent Benjamin Lawsky clarified soon after that the goal was not to control miners, developers or people who use Bitcoin. The second version includes the explicit language that was mentioned earlier. buy Sample Email database online

Requirements.Ifthe regulations take effect and you’re among the entities that are covered that are required to apply for an authorization. In order to apply for a license, you will find a thorough proposal, which you can study however, generally speaking you must provide details about the owner of your company, your financials, as well as insurance details, including your business plan generally, to permit the NYDFS to determine what you’re about and how secure that you’re, from where the cash comes from, as well as the things you’re planning to accomplish. You also have to pay a fee for application. Sample email lists

If you are granted an authorization, you’ll be required to submit updated details to NYDFS regarding the items we’ve listed, such as finance, ownership and so on. It is required to present periodic financial statements so that NYDFS can track how your financial situation is. It is required that you buy Sample Email  database maintain an account of financial reserves and the amount will be determined by NYDFS depending on various variables concerning your company.

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Sample Email database free download

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There are specific rules regarding aspects like how to maintain custody of assets of consumers. There are anti-money laundering regulations that could or won’t override what’s already stipulated under existing laws. There are rules regarding having a security plan , penetration testing and other. There are regulations for disaster recovery. You must have a disaster recovery plan that is in line with various requirements. Sample Email  id list

There are rules regarding recording keeping. You must keep records and provide them to the NYDFS in certain situations. You must have written policies regarding compliance. Additionally, you must identify an official in your company who is in charge of compliance and who has the required accountability and authority. It is a requirement to expose the risk to consumers in order to let them know the risk of doing business with your company.

As you can observe the requirements are significant and are similar to the kind of conditions for mutual funds or openly traded company. The NYDFS has to decide on what it will do about the plan Sample email lists

— should either withdraw it, release the document in its present form or make additional changes. With that decision, they’ll issue document that outlines the reasoning behind what they’ve chosen to decide to do.

If something similar to the BitLicense is put into place in the near future, it will be significant in the development of Bitcoin. There would be a scenario where NYDFS isn’t the only one however, but possibly other jurisdictions would begin to regulate, and you’d begin to observe Bitcoin companies move closer to the model of financial institutions that are controlled. buy Sample Email database online

This is a decision that is in some ways opposed to the cypherlibertarian or cypherpunk views of what Bitcoin ought to be yet on the other hand , there’s an inescapable possibility that, once Bitcoin was deemed to be a valuable asset, Bitcoin businesses became big enterprises, and governments became involved, regulations would follow. Bitcoin businesses are a direct link between real people as well as the fiat currency market. If Bitcoin is significant enough to have a significant impact and is large enough to be regulated. It’s a change from what the early supporters of Bitcoin believed they were thinking of however, in a different way it is a sign of the Bitcoin system growing and integrating into the economy, which is more tightly controlled. Whatever your opinion regarding it, regulations are getting underway and if you’re thinking of in launching your own Bitcoin business , you should be on the lookout for this development.

Can this be considered a success? There are many methods to consider this, but here’s a way to determine the effectiveness of regulation such as BitLicense in relation to the goal of public policy, which is improving the performance of Bitcoin companies: If something similar to BitLicense is put into place and companies begin advertising to customers who aren’t from New York that they can be trusted due to having an BitLicense and the argument is convincing to customers when choosing an organization to deal with, then regulations will work in the manner that its proponents would like it to. If that happens and how it affects what’s to come for Bitcoin is something we’ll need to wait and watch. Sample email lists

Alternative Mining Puzzles

Mining puzzles form the fundamentals of Bitcoin due to their difficulty, which restricts the capacity of any side to manage the process of consensus. Since Bitcoin miners are paid for solving the puzzles they complete, it is reasonable to anticipate that they’ll invest a lot of time looking for ways to solve these puzzles quicker or more efficiently with the intention of increasing the amount of money they earn. However If there’s something that benefits the network, but doesn’t directly assist them in solving the puzzles faster, miners may be encouraged to avoid it in order to reduce their expenses. The layout of the puzzle has a crucial part in directing and directing participation within the network. marketing database Sample Email

In this section we’ll discuss various possible alternatives to puzzle designs, in the event that we can modify Bitcoin’s puzzle, or even create an entirely new design from scratch. One of the most popular design challenges is to create an ASIC-resistant puzzle that is able to level the playing field for users using conventional computing equipment and those equipped with custom-designed hardware. What else can we create the puzzle to accomplish? What other types of behavior do we want to encourage or dissuade? We’ll look at some examples that have fascinating properties, ranging from reducing consumption of energy to having positive social effects, to preventing mining pools from being formed. Some of these are utilized by altcoins, whereas other are research ideas that could be utilized in the near future.

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Sample Email b2c database

Essential Puzzle Requirements

The first step is to look at some of the most important security rules that are required for puzzles mining. It’s not doing us much good to add extravagant new features in a game if it can’t fulfill the essential specifications needed to remain Bitcoin safe. buy Sample Email  database

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There are numerous requirements that could be met that we’ve discussed in Chapters 2 and 5. Mining puzzles must be easy to verify since every network node is able to verify every puzzle’s answer -even those not directly involved in mining and include SPV clients. We also want to provide an adjustable difficulty, to ensure that the difficulty of the puzzle could be adjusted in the course of time as new users are added to the network with greater quantities of hash power that they contribute. This allows this puzzle to be challenging enough that attacks on the chain are costly, however, puzzle solutions can still be found in a steady manner (about once every 10 seconds in Bitcoin). buy Sample Email database online

What exactly is the mining puzzle of Bitcoin? At present, we’ve referred to this “Bitcoin’s puzzle.” More specifically, we can refer to it a partial hash-preimage problem, since the aim is to find preimages that match a partial output of a hash — specifically an output that falls that is below a specific target. Another rare property might be used, for instance discovering a block that is at a minimum of the k bits that are zero, but using the output as an ideal value is likely to be the most straightforward.

It’s simple to see the way that Bitcoin’s SHA-256 hash-based puzzle is already meeting the two requirements. It is possible to make it significantly more difficult by changing the one parameter (the goal). The process of checking solutions is simple and requires only one SHA-256 calculation and a check, no regardless of how difficult the problem is to resolve. marketing database Sample Email

Progress-freeness.Another central requirement is more subtle: the chance of winning a puzzle solution in any unit of time should be roughly proportional to the hash power used. This means that miners who have extremely powerful hardware will only enjoy a an advantage of a proportional amount in that next miner to discover an answer to a puzzle. Even miners with smaller equipment should have a probability of succeeding and getting a reward.  Sample email lists

To illustrate this Let’s consider the wrong puzzle that does not fulfill this requirement. Take a puzzle in mining that requires n steps to solve. In this case instead of locating the block whose SHA256 hash is less than a particular threshold, we might need to consider the computation of nconsecutive SHA256 hashes. This isn’t a good way to determine, but forget about it for the moment. The biggest issue is that because it takes precisely n steps to come up with a solution then the most efficient miners in the network will be the one who gets the next prize. It would soon be obvious who was the one solving each problem, and the other miners will not be able to join in at all.

Another thing to note is that a well-designed puzzle offers every miner the possibility of winning the next puzzle according in the hashpower they generate. Think about throwing your dart on the board in random order, with different sizes of targets, which represent the mining power of various miners. If you consider it this way this way, your chances of solving the problem must be independent of the amount of time you’ve spent in trying to figure it out (because large miners are always doing more time). This is why a quality mining puzzle is known as progress-free. marketing database Sample Email

From a mathematical point of view This means that a great mining puzzle should be an unremembered processotherwise, it will reward miners for their past achievements somehow. Thus, any puzzle that can be solved will require some kind of trial-and-error. The time required to come up with the solution will consequently be an exponentially distributed distribution as we have seen in Chapter 2.

Flexible difficulty, speedy verification and progress-freeness are the three essential characteristics in Bitcoin mining puzzles. The partial pre-image finding based on SHA-256 meets all three. Some argue that additional aspects that Bitcoin’s mining puzzle fulfills are also important and we’ll look at additional requirements that could appear while we investigate various other possible uses for the technology.

ASIC-resistant puzzles

We’ll start with the challenge of designing an ASIC-resistantpuzzle, which has been by far the most widely discussed and sought after type of alternative mining puzzle. In chapter 5, Bitcoin mining was initially performed using standard computers, but was later expanded to GPUs and custom FPGA equipment, but today is mostly done with extremely powerful and designed ASIC chips. marketing database Sample Email

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ASICs ASICs are significantly more efficient than standard computing equipment that mining on an average computer (or even some of the early generation ASICs) is no longer worth the cost of electricity even if the hardware is available for free. buy Sample Email database online

The change has meant that the majority of people taking part in this Bitcoin ecosystem (for example , customers or merchants who transact through Bitcoin) are no longer able to play any involvement with respect to mining. Many people believe that this is a risky move as a smaller number of professional miners governing their mining processes. In the original paper of Satoshi Nakamoto on Bitcoin”one-CPU-one-vote” was the key phrase “one-CPU-one-vote” was used, that has been interpreted to refer to Bitcoin must be an open system that is that is owned by all its users.

Some believe that the growth in ASICs will be inevitable but not at the expense of Bitcoin and the motivation behind ASIC-resistance is just people wanting to return to “the good old days.” Without deciding on whether or not ASIC-resistance is a good idea or not, let us look at the technical issues and possible strategies to achieve this objective. Sample email lists

In general we are trying to discourage the usage of

Custom-designed hardware designed to be used for mining. If you interpret this in a strict way, it would mean creating a puzzle in which general-purpose computers are among the least expensive and most efficient. This isn’t feasible. Since general purpose computers already have specific-purpose optimized. There are a few products that offer the same advantages and they evolve with the passage of the passing of time. For instance, in the past 10 years, Intel as well as AMD have added support for special directions (often known as “adding hardware support”) to process the AES block cipher faster. Thus, certain computers will always be slower than others in mining. In addition, it’s difficult to imagine creating a mining puzzle that is dependent on the features such as speakers and monitors that the majority of personal computers have. Thus, machines that are specially designed to remove these features could be less expensive and more efficient. Sample email lists

Our goal is less ambitious that is to create an algorithm that can narrow the gap between affordable and efficient customized hardware and the general-purpose computers accomplish. ASICs will always be more efficient, however should we reduce this to a certain order more or less, it may still be economically feasible for individuals to mine using the computer they already own.

Memory-hard puzzles.The most popular puzzles specifically designed to be ASIC-resistant are known as memory-hardpuzzles, puzzles that need a huge amount of memory to be able to compute in lieu of,, or even in lieu of lots of CPU time. Another similar, but distinct concept is memory-boundpuzzles where the time it takes to access memory is the main factor that determines the time to compute. The puzzle could be memory-hard and not be memory-bound or it could be memory-bound and not be memory-hard or both. This is a subtle but significant distinction that comes from the fact that, even if the speed of CPU is the main factor in computation, the cost of solving many of these puzzles in parallel will still be determined by the expense of memory or the reverse is true. For a typical computational puzzle we’re looking for something memory-hard and memory-bound, which means that a significant amount of memory is needed and this is the primary element. Sample email lists

Why could memory-bound and memory-hard puzzles benefit ASIC resistance? The logic-based operations required to calculate modern hash functions are just a fraction of the process that takes place within a CPU, which means that, for Bitcoin’s puzzle ASICs benefit from a great deal of value by not having to implement all of the functions that are unnecessary. A similar issue is that the variance in performance of memory (and cost per performance) is significantly less than the variance in processing speeds between different kinds of processors. Therefore, if we could create an object that is difficult to solve, and requiring a relatively easy computation but plenty of memory which means that you would have to pay for solving a problem will decrease at the lower cost of memory improvement.

The SHA-256 algorithm is definitely not memory-hard like we’ve previously seen it requires only a small state of 256 bits that can easily fit into the CPU registers. However, it’s not that difficult to construct a memory-hard proof of-work puzzle.

Scrypt.The most well-known memory-hard puzzle is referred to as Scrypt. The puzzle is currently frequently utilized in Litecoin which is the second most widely used cryptocurrency, as well as many alternative Bitcoin alternatives. Sample email lists

The memory-hard hash feature that was originally developed to hash passwords in a manner that is not easy to brute force and therefore the mining puzzle is similar to bitcoin’s partial hash-preimage puzzle, but by replacing SHA-256 with Scrypt.

It is interesting that the fact that Scrypt was in existence before Bitcoin and was utilized to hash passwords gives assurance of its security. Hashing passwords is the same goal as ASIC resistance, as for security we need an attacker who has specific hardware to be able to calculate password hashes at a much faster rate than a legitimate user and server who use computers that are general-purpose. Sample email lists

Scrypt is basically a process that involves two steps. The first involves the filling of a large amount filled with Random Access Memory (RAM) by storing random information. The second stage involves taking data from (and updating) the memory, in pseudorandom manner which requires all of the buffer be saved in RAM. marketing database Sample Email

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To comprehend why scrypt can be described as memory-intensive, imagine trying to calculate the same number without buffer V. It is certainly possible , but in the ninth line, we’d have to compute V[j]’s value in real time this would require an j number of times SHA-256. Since J’s value in each loop will be chosen pseudorandomly in between N-0 it will take about N/2 SHA-256 calculations. The whole function will be the form of N*N/2. buy Sample Email database online
2
N /2 SHA-256 computations instead of 2N if there is a buffer! Therefore, using memory transforms
2 2 scrypts using an O(N) function, converting it to O(N ). It should be easy to select an N that is sufficient to match is larger than the O(N )
isn’t fast enough, so using memory can be faster.

Time-memory tradeoffs.While it is more difficult to compute scrypt with the aid of a huge memory buffer, it’s nevertheless possible to use less memory in exchange of some additional computation. Imagine that we are using an N/2-sized buffer (instead of the size N). We can now save only the V[j] that are even, and discard those values where the value is odd. The second step is around 50% of the time, an odd value of j is selected, however this is relatively simple to calculate quickly — we just compute SHA-256(V[j-1[j-1]) because V[j-1] will be stored in our buffer. Since this occurs about 50% of the time, it requires N/2 additional SHA-256 computations. Sample Email business  database free download

So, the reduction of memory requirements by halving increases the number of SHA256 computations by half (from 2N up to 5N/2). In general, we’re able to save only every 1st row in the buffer V by using the memory N/k and computing (k+3)N/2 iterations of SHA256. If one sets k to be N we’re back to
2
Our earlier calculation showed that the running time is O(N ). These numbers do not apply specifically for scrypt by itself, however the asymptotic estimates are applicable
There are alternative designs that reduce the possibility of trading off memory in time. For example, if a buffer is constantly updated during the second loop this renders the time-memory tradeoff less efficient since the updates need to be saved.

Verification cost.Another issue with Scrypt is that it needs more time to check as it takes to calculate. To make memory hardness a valid factor, N must be significant. This means that a single calculation of scrypt will be orders of many times higher than a single repetition of SHA-256. This is the only thing needed to determine Bitcoin’s less complicated mining problem. Sample email lists

It has negative implications for every client in the network is required to run this calculation again to confirm that a new block is actually valid. This can slow the propagation and acceptance of the new blocks, and increase the possibility of forks. Also, each client (even light SPV clients) will require enough memory to process the operation effectively. Therefore, how much memory which can be used to compute the scrypt function in a cryptocurrency is restricted by practical considerations. Sample Email business  database free download

It wasn’t until recently that it was yet known if it was possible to create the mining algorithm that is memory-hard to compute , yet quick (and easily) in its verification. This feature isn’t useful in password hashing which was the main use-case for memory-hard functions prior to their use in cryptocurrency.

The year 2014 saw the introduction of a brand-new puzzle dubbed Cuckoo Cycle was suggested in the work of John Tromp. Cuckoo Cycle is based on the problem of identifying cycles in the graph created from the cuckoo hash table the data structure itself was first proposed in 2001. There’s no way to calculate it without setting up a huge hash table. However, it can be verified by ensuring whether it is found. (relatively tiny) cycle is found.

This could make memory-hard or memory-bound proof of works far more feasible to usage to create Bitcoin consensus. There isn’t any scientific proof that this feature cannot be efficiently computed without the need for memory. Most of the time new cryptographic algorithms seem secure, however the community isn’t convinced until they’ve been in use for a long time without being attacked. Because of this and in light of the recent revelation, Cuckoo Cycle has not been employed in any cryptocurrency until 2015. Sample email lists

Scrypt in practice.Scrypt has been utilized in numerous cryptocurrency, including a few prominent ones, like Litecoin. Its results are inconsistent. Scrypt ASICs are available now to the parameters used by the Litecoin (and copied by a variety of altcoins). It is surprising that the performance improvement of these ASICs when compared to general-purpose computers is equal to or higher than that for the SHA-256 algorithm! So, scrypt was definitely not ASIC-resistant, in the end, at the case is with Litecoin. The creators of Litecoin initially believed that ASIC resistance was the main benefit over Bitcoin However, they has since acknowledged it is no longer the situation. Sample Email business  database free download

This could be because of the low amount of the N (the measure of the memory use) that Litecoin uses that requires only 128kB of memory to compute (or less in the event that a time-memory tradeoff was employed, which is typically executed using GPUs to make the full buffer to fit in the faster cache). This makes it easy to design light mining ASICs with no complicated memory access bus that is required to access gigabytes in RAM, similar to the amount that general purpose computers have. Litecoin developers didn’t select an amount that was more (which makes ASICs more difficult to create) due to the cost of verification too expensive.

Alternative approaches to ASIC-resistance. Remember that our initial goal was to make it difficult to create ASICs that have a dramatic speed increase. Memory-hardness is just one method towards this goal, and there are many more.

The other options, unfortunately they aren’t as scientific and haven’t been as thoroughly analyzed or designed for memory-hard features. The most popular is known as X11 it is an amalgamation of 11 various hash functions that were introduced by an altcoin known as Darkcoin (later changed to DASH) and later adopted by many other cryptos. The purpose for X11 will make it much more difficult to create an effective ASIC because all 11 functions need to be implemented into hardware. This is really only an inconvenience for designers of hardware. If an ASIC was developed to run X11 It would certainly render GPU and CPU mining obsolete. marketing database Sample Email

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Sidebar: Where did the X11’s hash functions originate from? From 2007 until 2012 between 2007 and 2012, US National Institute of Standards conducted a competition to select an entirely new family of hash function that would be the standard SHA-3. This resulted in a wide range of hash function that were submitted as candidate along with the design documents as well as the source code. While many of them were not cryptographically secure in the course of the competition 24 of them survived without known security issues. X11 selected 11 of them which included Keccak who was the final contest winner. Sample Email  database providers

Another approach which has been proposed, but not actually implemented, is to have a mining puzzle that’s a moving target. That is, the mining puzzle itself would change, just as the difficulty periodically changes in Bitcoin. Ideally, the puzzle would change in such a way that optimized mining hardware for the previous puzzle would no longer be useful for the new puzzle. It’s unclear exactly how we would actually change the puzzle once every so often in order to obtain the security requirements we need. If the decision were to be made by the developers of an altcoin, it might be an unacceptable source of centralization. For example, the developers might choose a new puzzle for which they have already developed hardware (or just an optimized FPGA implementation), giving them an early advantage.

Perhaps the sequence of puzzles could be generated automatically, but this seems difficult as well. One idea might be to take a large set of hash functions (say, the 24 SHA‐3 candidates which were not broken) and use each for six months to one year, too short of a time for hardware to be developed. Of course, if the schedule were known in advance, then the hardware could simply be designed just in time to ship for the time each function was being used. Sample Email quality  lists

The ASIC honeymoon. The lack of ASICs for X11 so far, even though they are clearly possible to build, demonstrates a potentially useful pattern. Because no altcoins using X11 have a particularly high market share, there simply hasn’t been a large enough market for anybody to build ASICs for X11 yet. In general, designing ASICs has very high upfront costs (in both time and money) and relatively low marginal costs per unit of hardware produced. Thus, for new and unproven cryptocurrencies, it is not worth making an investment to build hardware if the currency might fail before the new hardware is available for mining. Even when there is a clear market, there is a time delay before hardware units will be ready. It took over a year for the first Bitcoin ASICs to be shipped from when they were first designed, and this was considered to be lightning fast for the hardware industry. Sample email lists

Thus, any new altcoin with a new mining puzzle is likely to experience an ASIC honeymoonduring which time GPU and FGPA mining (and potentially CPU mining) will be profitable. It may not be possible to stem the tide of ASICs forever, but there is perhaps some value in making it appealing for individuals to participate in mining (and earn some units of the new currency) while it is bootstrapping.

Arguments against ASIC‐resistance. We’ve seen that it may be impossible to achieve ASIC‐resistance in the long run. There are also arguments that it is risky to move away from the relatively proven SHA‐256 mining puzzle towards a new puzzle that might be weaker cryptographically. Furthermore, SHA‐256 mining ASICs are already being designed at close to modern limits on hardware efficiency, meaning the exponential growth period is probably over and SHA‐256 mining will therefore offer the most stability to the network.

Finally, there is an argument that even in the short run ASIC‐resistance is a bad feature to have. Recall from Chapter 3 that even if there is a 51% miner, many types of attack aren’t rational for them to attempt because it could crash the exchange rate and decimate the value of the miner’s investment in hardware since the bitcoins they earn from mining will be worth much less. Sample Email quality  lists

With a highly ASIC‐resistant puzzle, this security argument might fall apart. For example, an attacker might be able to rent a huge amount of generic computing power temporarily (from a service such as Amazon’s EC2), use it to attack, and then suffer no monetary consequences as they no longer need to rent the capacity after the attack. By contrast, with an “ASIC‐friendly” puzzle, such an attacker would inherently need to control a large number of ASICs which are useful only for mining the cryptocurrency. Such an attacker would be maximally invested in the future success of the currency. Following this argument to its logical conclusion, to maximize security, perhaps mining puzzles should not only enable efficient mining ASICs to be be built, but be designed such that those ASICs are completely useless outside of the cryptocurrency! Sample Email consumer  database

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Proof‐Of‐Useful‐Work

In Chapter 5 we discussed how the energy consumed (some would say wasted) by Bitcoin mining, referred to as negative externalitiesby economists, is a potential concern. We estimated that Bitcoin mining consumes several hundred megawatts of power. The obvious question is whether there is some puzzle for which the work done to solve it provides some other benefit to society. This would amount to a form of recycling and could help increase political support for cryptocurrencies. Of course, this puzzle would still need to satisfy several basic requirements to make it suitable for use in a consensus protocol. Sample Email  database providers

Previous distributed computing projects. The idea of using idle computers (or “spare cycles”) for good is much older than Bitcoin. Table 8.3 lists a few of the most popular volunteer computing projects. All these projects have a property that might make them suitable for use as a computational puzzle: specifically, they involve some sort of a “needle in a haystack” problem where there is a large space of potential solutions and small portions of the search space can be checked relatively quickly and in parallel. For example, in SETI@home volunteers are given small portions of observed radio signals to scan for potential patterns, while in distributed.net volunteers are given a small range of potential secret keys to test. Sample email lists

Volunteer computing projects have succeeded by assigning small portions of the solution space to individuals for checking. In fact, this paradigm is so common that a specific library called BOINC (Berkeley Open Infrastructure for Network Computing) was developed to make it easy to parcel out small pieces of work for individuals to finish. Sample Email quality  lists

In these applications, volunteers were motivated mainly by interest in the underlying problem, though these projects also often use leaderboards for volunteers to show off how much computation they have contributed. This has led to some attempts to game the leaderboards by reporting work that wasn’t actually finished, requiring some projects to resort to sending a small amount of redundant work to detect cheating. For use in a cryptocurrency, of course, the motivation is primarily monetary and we can expect participants to attempt to cheat as much as technically possible.

Challenges in adapting useful‐proof‐of‐work. Given the success of these projects, we might attempt to simply use these problems directly. For example, in the case of SETI@Home, where volunteers are given segments of radio observations which they test for statistical anomalies, we might decide that statistical anomalies which are rarer than some threshold are considered “winning” solutions to the puzzle and allow any miner who finds one to create a block.

There are a few problems with this idea. First, note that potential solutions are not all equally likely to be a winning solution. Participants might realize that certain segments are more likely to produce anomalies than others. With a centralized project, participants are assigned work so all segments can be analyzed eventually (perhaps with more promising segments given priority). For mining, however, any miner can attempt any segment, meaning miners might flock to try the most likely segments first. This could mean the puzzle is not entirely progress‐free, if faster miners know they can test the most promising segments first. Compare this to Bitcoin’s puzzle, in which any nonce is equally likely to any other to produce a valid block, so all miners are incentivized to choose random nonces to try. The problem here demonstrates a key property of Bitcoin’s puzzle that we previously took for granted, that of an equiprobable solution space. Sample email lists

Next, consider the problem that SETI@home has a fixed amount of data to analyze based on observations taken by radio telescopes. It’s possible that as mining power increased, there would be no more raw data to analyze. Compare this again to Bitcoin, in which an effectively infinite number of SHA‐256 puzzles can be created. This reveals another important requirement: an inexhaustible puzzle spaceis needed. purchase Sample Email  lists

Finally, consider that SETI@home uses a trusted, centralized set of administrators to curate the new radio data and determine what participants should be looking for. Again, since we are using our puzzle to build a consensus algorithm we can’t assume a centralized party to manage the puzzle. Thus, we need a puzzle that can be algorithmically generated.

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Which volunteer computing projects might be suitable as puzzles?. Returning to Figure 8.3, we can see that SETI@home and Folding@home clearly won’t work for a decentralized consensus protocol. Both probably lack all three properties we’ve now added to our list. The cryptographic brute‐force problems taken on by distributed.net could work, although they are typically chosen in response to specific decryption challenges that have been set by companies looking to evaluate the security of certain algorithms. These can’t be algorithmically generated. We can algorithmically generate decryption challenges to be broken by brute forcing, but in a sense this is exactly what SHA‐256 partial pre‐image finding already does and it serves no beneficial function. Sample Email consumer  database

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This leaves the Great Internet Mersenne Prime Search, which turns out to be close to workable. The challenges can be algorithmically generated (find a prime larger than the previous one) and the puzzle space is inexhaustible. In fact, it’s infinite, since it has been proven that there are an infinite number of prime numbers (and an infinite number of Mersenne Primes in particular). Sample Email  database providers

The only real drawback is that large Mersenne Primes take a long time to find and are very rare. In fact, the Great Internet Mersenne Prime Search has found only 14 Mersenne primes in over 18 years! It clearly wouldn’t work to add less than one block per year to a block chain. This specific problem appears to lack the adjustable difficulty property that we stated was essential in Section 8.1. It turns out, however, that a similar problem involving finding prime numbers appears workable as a computational puzzle. Sample email lists

Now, to turn this into a computational puzzle, we need three parameters m,n,and kwhich we will explain momentarily. For a given challenge x(the hash of the previous block), we take the first mbits of xand consider any chain of length kor greater in which the first prime in the chain is an n‐bit prime and has the same mleading bits as xto be a valid solution. Note that we can adjust nand kto make the puzzle harder. Increasing k(the required chain length) makes the problem exponentially harder, while increasing n(the size of the starting prime) makes it linearly harder. This provides fine‐tuning of the difficulty. The value of mjust needs to be large enough that trying to pre‐compute solutions before seeing the value of the previous block is infeasible. purchase Sample Email  lists

This provides strong evidence that it is possible to make proof‐of‐useful‐work practical in some limited circumstances. Of course, it’s debatable the extent to which finding large Cunningham chains is useful. It’s possible that they may have some applied purpose in the future and they certainly stand as a small contribution to our collective mathematical knowledge. Currently, however, they have no known practical applications.

Permacoin and proof‐of‐storage. A different approach to proof‐of‐useful work is proof‐of‐storage (also sometimes called proof‐of‐retrievability). Rather than requiring a solely computational puzzle, what if we could design a puzzle that required storing a large amount of data to compute? If this data were useful, then miners’ investment in mining hardware would effectively be contributing to a widely distributed and replicated archival storage system. Sample email lists

We’ll take a look at Permacoin,the first proposal for proof‐of‐storage for use in consensus. We begin with a large file which we’ll call F.For now, let’s assume everybody agrees on the value of Fand the file will not change. For example, Fmight be chosen by a trusted dealer when a cryptocurrency is launched, much as any new currency needs to agree on a genesis block to get going. This would ideally be a file of public value. For example, experimental data collected from the Large Hadron Collider already consists of several hundred petabytes (PB). Providing a free backup to this data would be quite useful. purchase Sample Email  lists

Of course, since Fis a huge file most participants will not be able to store the entire file. But we already know how to use cryptographic hash functions to ensure everybody agrees on Fwithout knowing the entire thing. The simplest approach would be for everybody to agree on H(F),but a better approach is to represent Fusing a large Merkle tree and have all participants agree on the value of the root. Now, everybody can agree on the value of Fand it is efficient to prove that any portion of Fis correct.

As usual, this is a slight simplification of the full Permacoin proposal, but this is enough to understand the key design components. The biggest practical challenge, of course, is finding a suitably large file that is important, public and in need of additional replication. There are also significant complexities if the file Fchanges over time, as well as with adjusting the mining difficulty over time.

Long‐term challenges and economics. To summarize this section, proof‐of‐useful‐work is a very natural goal, but it is quite challenging to achieve it given the other requirements of a good computational puzzle for a consensus protocol. Although at least two examples are known which are technically feasible, Primecoin and Permacoin, both carry some technical drawbacks (primarily longer verification time of purported solutions). Furthermore, both provide fairly minor public benefits compared to the scale of effort we’ve seen levied at Bitcoin mining with millions of dollars worth of capital and megawatts of electricity consumed. Sample Email consumer  database

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There is an interesting economic argument that the benefit of any proof‐of‐useful‐work should be a pure public good.In economics, a public good is one that is non‐excludable, meaning nobody can be prevented from using it, and non‐rivalrous, meaning the good’s use by others does not affect its value. The classic example is a lighthouse. Sample Email address lists

Some of the examples we discussed here, such as protein folding, might not be a pure public good because some firms (such as large pharmaceutical corporations) may benefit more from increased knowledge about protein folding than others. Essentially, mining would be cheaper for these parties since they are gaining more benefit from the public benefits than others would be.

Nonoutsourceable Puzzles

Let’s turn to another potential design goal for alternative mining puzzles: preventing the formation of mining pools. As we discussed in Chapter 5 and elsewhere, most Bitcoin miners mine as part of a pool rather than independently. This has resulted in a few large pools which together represent most of the mining power. Since each pool is operated by a central pool administrator, some feel this is a dangerous trend away from Bitcoin’s core design principle of decentralization and can compromise its security. Sample email lists

While a mining pool with a majority share is an obvious problem, any large centrally managed pool might implement a non‐default mining strategy and attack the network. Such pools are also a juicy target for hackers to try and compromise to immediately control a large amount of mining power. The pool operators might collude to censor transactions or enforce high transaction fees. At the very least, having most miners in pools also means that most miners aren’t running a fully validating node.

Interestingly, these concerns have an analogy in the realm of voting. It’s illegal in the United States and many other nations for individuals to sell their vote. Arguably participating in a pool controlled by someone else is akin to selling your vote in the Bitcoin consensus protocol. buy Sample Email targeted  list

Technical requirements for pools. Recall that mining pools appear to be an emergent phenomenon. There’s no evidence that Satoshi was thinking of mining pools at the time of Bitcoin’s original design. It wasn’t apparent for a few years that efficient pools could be run between many individuals who don’t know or trust each other.

As we saw in Chapter 5, mining pools typically work by designating a pool operator with a well‐known public key. Each of the participating miners mines as usual but sends in shares to the pool operator. These shares are “near misses” or “partial solutions” which would be valid solutions at a lower difficulty level. This shows the pool operator how much work the miner is performing. Whenever one of the pool participants finds a valid block, the pool operator then distributes the rewards amongst the pool participants based on the number of shares they have submitted. As we discussed in Chapter 5, there are many formulas for dividing the revenue up, but all mining pools follow this basic structure. Sample email lists

The existence of pools thus relies on at least two technical properties of Bitcoin. The first is that it’s easy for a miner to prove (probabilistically) how much work they are doing by submitting shares. By choosing a low enough threshold for shares, miners can easily prove how much work they are performing with arbitrary precision regardless of the actual difficulty of finding an valid block. This facet of mining puzzles appears difficult to change, given that we need a puzzle that can be created with arbitrary difficulty.

Second, pool members can easily prove to the pool operator that they’re following the rules and working to find valid blocks which would reward the pool as a whole. This works because the pool’s public key is committed to in the coinbase transaction included in the block’s Merkle tree of transactions. Once a miner finds a block or even a share, they can’t change which public key is the recipient of the newly minted coins.

Block discarding attacks. There is one weakness in this scheme for implementing mining pools: there is nothing to to enforce that participating miners actually submit valid blocks to the pool manager in the event that they find them. Suppose that there’s a pool member that’s upset with a large mining pool. They can participate in the pool by mining and submitting shares just like normal, but in the event that they actually find a valid block that would reward the pool they simply discard it and don’t tell the pool operator about it. buy Sample Email targeted  list

This attack reduces the pool’s overall mining power as none of the attacker’s work is contributing towards finding valid blocks. However the attacker will still be rewarded as they appear to be submitting valid shares and simply getting unlucky to not find any valid blocks. If the mining pool is designed to be revenue‐neutral (that is, all mining rewards are redistributed back to participants) then this attack can cause the pool to run at a loss. Sample email lists

This attack is sometimes called a vigilanteor sabotageattack and is considered a form of vandalism because the attack appears to be costly for both the attacker and the pool. The attacker loses money because every block they discard would have led to some proportion of the block rewards being returned to them. Of course, the attacker still gets rewards for other puzzle solutions that are found. Sample Email  database free

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It appears that a rational attacker wouldn’t employ this strategy, since they would lose money without gaining anything tangible. It turns out (quite surprisingly) that there are cases where this strategy can be profitable, as discussed in the box below. But in any case, we want to design an entirely new mining puzzle formulation that ensures this strategy is always profitable. Sample Email address lists

Sidebar: block discarding attacks between pools. People assumed for years that it can’t be profitable for a participant to discard valid blocks found on behalf of the pool. It turns out this strategy can be profitable if one mining pool uses it to attack another. This was proposed apocryphally many times and first thoroughly analyzed in a paper by Ittay Eyal in 2015.

Let’s consider a simple case: suppose two mining pools, A and B, each have 50% of the total mining capacity. Now suppose B uses half of its mining power (25% of the total capacity) to mine as a member in pool A, but discards all blocks found. We can show, in a simplified model, that B will now earns 5/9 of the total rewards, greater than the 50% it would earn by mining normally. In this simple case, dedicating half of its mining power to attacking can be shown to be the optimal strategy for pool B.

The situation grows more complicated with multiple pools. Block discarding has not been observed in practice on a large scale as of this writing. But it remains possible that in the long run, attacks like this one will throw the viability of large mining pools into question. Sample email lists

Rewarding sabotage. Our design goal is to make it so that miners are incentivized to mine in a pool but not submit valid blocks to the pool manager. Currently, only the pool manager can collect the mining rewards because the manager requires all participants to include a specific public key in the coinbase transaction of blocks they are mining. Proper inclusion can be easily checked in submitted partial solutions. The pool manager is the only party that knows the private key and hence can determine where the newly minted coins go. buy Sample Email targeted  list

But what if we required that all participants also knew the private key (and hence could redirect the funds after mining a block?). To do this, we need a puzzle in which each solution attempt requires knowledge of the private key in the coinbase transaction. We can change the puzzle from “find a block whose hash is below a certain target” to “find a block for which the hash of a signatureon the block is below a certain target.” This signature must be computed using the same public key in the coinbase transaction.

Such a puzzle leaves would‐be pool operators with two untenable choices. They might distribute the private key to all pool participants, in which case any of them can steal all of the funds. Alternately, they can perform the signatures on behalf of pool participants. Computing a signature is orders of magnitude more expensive than computing a hash, however, so in this case the pool manager would be doing the majority of the heavy lifting. It would be better for the pool manager to simply be a solo miner.

The pros and cons of non‐outsourceable mining. Since this puzzle can’t effectively be outsourced to an untrusted participant, it makes it much more challenging, if not outright impossible, to form a mining pool with untrusted participants. It effectively prevents allpools, even efforts like P2Pool to make a decentralized pool without a pool manager. buy Sample Email database for marketing Sample email lists

There’s an argument that deploying such a puzzle might perversely lead to morecentralization, not less, because it would discourage small miners from participating due to the high variance they would face. This would leave only large mining operations. Currently, while pools may nominally control a large amount of mining power, it isn’t clear that they can use this to launch an attack without seeing many of their members defect. It remains an open question which risk is worse — that of large mining pools, or of limiting mining to operators large enough to live with a high variance.

The holy grail would be to design a consensus protocol which is “naturally” low‐variance by rewarding miners a small amount for lower‐difficulty puzzles. This would mean miners don’t need to form pools and yet small miners may still participate. Simply decreasing the average time between blocks won’t work — it would need to be decreased by a factor of 1,000 or more for the resulting variance to be equivalent to today’s large mining pools. But then the delay between blocks would be less than a second and the number of stale blocks would be chaotically high. It remains an open question if there is an alternate version of the consensus protocol which would enable easier mining puzzles without requiring near‐instantaneous broadcast of all solutions. Sample Email  database free

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Proof‐of‐Stake and Virtual Mining

To wrap up this chapter, let’s look at the idea of replacing computational puzzles with virtual mining. This term refers to a disparate set of approaches but they all have in common that they require only a small expenditure of computational resources by participating miners. Sample Email address lists

Closing the loop on mining. As a thought experiment, suppose Bitcoin or another cryptocurrency becomes the dominant form of payment globally. Miners would start with some initial holding of cryptocurrency, use it to purchase mining equipment and electricity, consume these resources, and in the process, acquire new cryptocurrency in the form of mining rewards. This process continually burns energy and raw materials.

Once mining hardware becomes a commodity and electricity is a commodity (as it generally already is), no miner would have a significant advantage over any other miner in terms of how efficiently they could convert their initial cryptocurrency holdings into mining rewards. Barring minor variations in efficiency, whoever invests the most into mining will receive the most rewards. buy Sample Email database for marketing

The basic question motivating virtual mining is: what would happen if we removed the step of spending money on power and equipment? After all, this process is primarily used to prove who has invested the most in mining. Why not simply allocate mining “power” directly to all currency holders in proportion to how much currency they actually hold? Sample email lists

Recall that the original goal of Bitcoin mining was to enable a form of voting on the state of the block chain, with miners with more computing power gaining more votes. We could instead design our “voting” system so that votes are determined by how much currency one currently holds.

Advantages of virtual mining. The primary advantage of this approach is obvious: it removes the wasteful right half of the mining cycle from Figure 8.5, leaving us with a “closed” system as shown in Figure 8.6. buy Sample Email database for marketing

In addition to simplicity, this approach would dramatically reduce Bitcoin’s environmental footprint. It wouldn’t reduce energy consumption to zero, because miners will always have to expend some computational resources to communicate with the network and validate. Some virtual mining
schemes also require a small amount of computational mining as well. But in either case, the vast majority of the mining work performed in Bitcoin can potentially be eliminated.

Virtual mining may also reduce the trend towards centralization. Because there is no mining hardware involved there is no concern about an ASIC advantage; all miners are able to mine as “efficiently” as all others. Any virtual mining puzzle achieves all of the goals of ASIC‐resistant puzzles. Sample email lists

Perhaps most importantly, virtual mining might solve the problem which we discussed in the context of ASIC‐re