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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.

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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. Buy Psychiatrist Email Lists online.

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.

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 Buy Psychiatrist Email Lists online.

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.

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. Buy Psychiatrist Email Lists online.

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. Buy Psychiatrist Email Lists online.

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.

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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.

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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!

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. Buy Psychiatrist email address list online.

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.

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. Buy Psychiatrist email address list online.

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. Buy Psychiatrist email address list online. 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.

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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.

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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.

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. Buy Psychiatrist email id database online.

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.

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. Buy Psychiatrist email id database online.

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).

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. Buy Psychiatrist email id database online.

Now, to turn this into a computational puzzle, we need three parameters m,n,and kwhich we will explain momentarily. Buy Psychiatrist email id database online. 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.

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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.

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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. Buy Psychiatrist email ids directory online.

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.

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. Buy Psychiatrist email ids directory online.

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. Buy Psychiatrist email ids directory online.

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.

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. Buy Psychiatrist email ids directory online. Essentially, mining would be cheaper for these parties since they are gaining more benefit from the public benefits than others would be.

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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.

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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.

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 Psychiatrist email leads online.

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. Buy Psychiatrist email leads online.

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. Buy Psychiatrist email leads online.

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.

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This attack reduces the pool’s overall mining power as none of the attacker’s work is contributing towards finding valid blocks.

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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.

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. Buy Psychiatrist email outlook online.

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.

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. Buy Psychiatrist email outlook online.

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.

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 Psychiatrist email outlook online.

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.

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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.

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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 Psychiatrist mailing id lists online.

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. Buy Psychiatrist mailing id lists online.

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.

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. Buy Psychiatrist mailing id lists online.

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.

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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.

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Why not simply allocate mining “power” directly to all currency holders in proportion to how much currency they actually hold?

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.

In addition to simplicity, this approach would dramatically reduce Bitcoin’s environmental footprint. Buy Psychiatrist mailing directory lists online. 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. Buy Psychiatrist mailing directory lists online.

Perhaps most importantly, virtual mining might solve the problem which we discussed in the context of ASIC‐resistant puzzles, namely that miners may not be invested in the long‐term health of the currency. Anybody who holds any bitcoins is effectively a stakeholder in the currency, and a powerful virtual miner (such as one who holds 51% or more of all currency) is a very large stakeholder. They have an incentive to do things that would benefit the system as a whole because it increases the value of the coins that they hold. This argument is even stronger than the argument that a miner sitting on a large stock of mining equipment whose value depends on the future of the currency will not behave maliciously.

This is where the term proof‐of‐stakecomes from. Even more than eliminating mining and saving energy, perhaps the most fundamental motivation for virtual mining is to ensure that mining is done by stakeholders in the currency who have the strongest incentives to be good stewards of the system. Buy Psychiatrist mailing directory lists online.

Implementing virtual mining: Peercoin. There are many variations of virtual mining of which we’ll describe a few of the most common ideas. We should emphasize that these ideas have not yet been studied in a scientific and rigorous way, nor have they undergone the level of practical testing that proof‐of‐work has due to Bitcoin’s popularity.

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To start with, we’ll consider the approach taken by Peercoin, which was launched in 2012 as the first

altcoin using proof‐of‐stake. Peercoin is a hybrid proof‐of‐work/proof‐of‐stake algorithm in which

“stake” is denominated by “coin‐age.”

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The coin‐age of a specific unspent transaction output is the

product of the amount held by that output and the number of blocks that output has remained

unspent. Now, to mine a block in Peercoin a miner must solve a SHA‐256 based computational puzzle

just like in Bitcoin. However, the difficulty of this puzzle is adjusted down based on how much

coin‐age they are willing to consume. To do this, the block includes a special “coinstake” transaction

in which some transactions are spent simply to reset their coin‐age to zero. Buy Psychiatrist mailing address lists online. The sum of the coin‐ages

consumed in the coinstake transaction decides how difficult the proof‐of‐work puzzle is to make a

given block valid.

It is possible for miners to mine with very little stake and a large amount of computational power, but the difficulty formula is chosen to make it dramatically easier to find a block if some coin‐age is consumed. The effect of the computational puzzle is mainly to ensure that the process is randomized if two miners attempt to consume a similar quantity of coin‐age.

Many virtual mining altcoins have adopted slightly different designs, including Nxt, BitShares, BlackCoin and Reddcoin. In each of these, some amount of stake is used to make a computational puzzle vastly easier, purportedly to the point that the computational puzzle is no longer the main challenge in mining. Buy Psychiatrist mailing address lists online.
Alternative kinds of stake. There are several alternative models to this hybrid should be discussed are:
* Proof-of-stake.The most fundamental form of proof of stake is to ease the process of mining for those who can prove they own a substantial amount of money. It is similar to Peercoin’s Proof-of-Coin-Age but without age being taken into consideration. The drawback of this method is that, unlike coin-age, that resets following success in mining, most wealthy participants always get the most straightforward mining puzzle. Buy Psychiatrist mailing address lists online.
* Proof-of-deposit.In this formula the moment that coins are used by a miner in order to create blocks, they are frozen for a specific amount of blocks. This could be thought of as a mirror image of coin-age. Instead of rewarding miners with coins that were not used for a long period of time before, this method rewards miners who agree to allow coins to remain in place for a prolonged period of period of time to come. In both cases, the miner’s stake comes due to the possibility of not being able utilize the coins for other activities.

The problem of no-stake. Virtual mining is an area of research in progress and there are many open issues. While some cryptocurrency has been created and were able to survive using virtual mining, they’ve had to endure the same challenge like Bitcoin to defend themselves against motivated attackers.

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The general vulnerability of virtual mining is known as the “nothing-at stake” issue (also known as the stake-grinding attacks.Suppose an attacker who has the proportion of 50% stake is trying to construct an kblock fork.

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We’ve already discussed that this attack is likely to fail due to a an extremely high likelihood, which increases exponentially by k.In conventional mining techniques, a failed attempt is a major chance cost because the miner could have earned mining profits during the mining process rather than spending resources in mining on the failed attack.

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Through virtual mining, this cost opportunity doesn’t exist. The miner is able to utilize his stake for mining the longest chain in the world as they attempt to make an fork. If their fork succeeds it will have consumed a significant portion part of the stake. Should it fail, evidence of its failure won’t be recorded in the final chain. Buy Psychiatrist mailing leads online.

Therefore, rational miners could be constantly trying to split the chain. Many attempts have been made to tackle this problem. The majority of virtual mining platforms have been more assertive in using checkpointing to stop lengthy forks, however as previously mentioned it’s more of a loop around an uncentralized consensus protocol.

In the case of Ethereum (an altcoin which was introduced in mid-2015, which we’ll be discussing in chapter 10) A idea known as Slasher permits punishment for miners who try to split the chain. In Slasher the process of using stake to mine, you must sign the current block using the private key that corresponds to the transactions comprising the stake that the miner holds. 

If a mining operator makes use of the stake that he signed to sign two different chains (neither of that is a prefix of one), Slasher allows miners to add these signatures later within the chain to prove of their behavior and receive some of the stake as a reward. Although this may be an efficient solution, the particulars for the procedure are complex and have yet to be successfully implemented. Buy Psychiatrist mailing leads online.

Another countermeasure that could be in place is the fact that, as we’ve witnessed for mining systems that are traditional miners might do not have the motivation to strike because it would cause harm to the system and weaken their stake even if the attack proves successful.

There are other disadvantages to virtual mining.Two additional disadvantages are worthy of noting. The first is that certain kinds of virtual mining even in the absence stake-grinding, could make certain types of attacks less difficult since it’s feasible for users to “save up” for a explosion in mining. For instance, a huge amount of coin-stake could be pooled in order to allow an explosive surge in mining, which could, for instance, start an alternative fork. This is even possible using a system such as Slasher is employed to stop mining across two chains simultaneously. To prevent this kind of attack Peercoin restricts the age limit to 90 days when calculating coin-age. Buy Psychiatrist mailing leads online.

Another issue is that if a mining user using a virtual mining system achieves 51% or more of stake, they are able to keep it for a lifetime by mining on the top that of their blocks. This is effectively becoming the owner of this block chain. Even if a stake comes up through mining rewards or transaction fees and transaction fees, the 51% miner will get the new stake, and their portion of the stake will gradually increase to 100 percent. In traditional mining even if the 51% miner is present, it is possible that a new miner will emerge with greater mining equipment and resources and decrease the number of miners. When mining virtual, it is more difficult to prevent this issue.

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Virtual mining is still a bit controversial within the main Bitcoin community. There is a belief that security requires burning of real resources, which requires real computing hardware and real power to discover the solutions to puzzles.

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If this theory is true that the apparent inefficiency of the verification of work system can be understood as the price of the security you receive. However, this theory hasn’t been established, just like the security of virtual mining hasn’t yet been established.

In sum there are a lot of things that one could modify about Bitcoin’s mining system This has been an area of intense research and ingenuity. To date, however none of the options appears to have proven theoretically sound and gained an actual use. For instance, although Scrypt is a well-known option for altcoins, it’s still not reached ASIC resistance and its value isn’t certain. It’s possible that alternative mining algorithms will be successful in the near future. In the end, Bitcoin itself came after years of unsuccessful attempts to develop a cryptocurrency. It was able to find the perfect place between good design and pragmatic trade-offs. Buy best psychiatrist email id lists online.

Bitcoin as a Platform

In the previous chapters we discussed the technical foundations of Bitcoin and discussed how it could be used as an alternative currency. We’ll now look at other applications that can be built using Bitcoin as the central component. Certain of them rely on Bitcoin as it is and without modifications and many would need only minor changes.

We’ve selected these applications based on the combination of practical utility as well as intellectual curiosity. The list isn’t necessarily comprehensive However, observing how these apps work (or could function, given that they are mostly thoughts or suggestions) can provide insight into the various ways that Bitcoin’s capabilities can be used to benefit others. Buy best psychiatrist email id lists online.

Bitcoin as an Append-Only Log

It’s beneficial to think of Bitcoin as an append-only log — the data structure on which it is possible to write new data and after we’ve written data, is impervious to manipulation and accessible for all time. Additionally, we have a secure concept of order that allows us to determine whether a particular piece of data was recorded to the log prior to or following another. This order is derived from block hash points, not the block’s timestamps. the timestamp of a block’s data may actually be less (earlier) amount than the one it preceded. 

This is because miners may be deceived about timestamps, miners’ clocks might not be in sync, and there may be delay in the network. However, if the block time stamp appears not to match by more than couple of hours, other miners will not accept it, which means we can trust that the timestamps are about right. We’ll find out that these properties can very useful. Buy best psychiatrist email id lists online.

Secure timestamping. The append-only log is used to construct an encrypted timestamping system using Bitcoin. We need to prove that we have the value of x at a particular date T.We may not wish to reveal xat T.Instead we want to reveal x when we actually complete an actual proof. This could be a lot later than T(and of course , if we had known it at T, we are still aware of it even after T). Once we’ve done the proof, we’d like that proof to remain in place.

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Remember from Chapter 1 that we could use hash functions to bind the data. Instead of publishing the data, we can commit it to hash functions.

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data x we want to prove the validity of, we could publish only the hashH(x) to the block chain. The
The properties of the function will ensure that we won’t find another value using the
the same value, yxsuch that H(x) equals H(y).We can also count on the logical fact that the hash the number x
isn’t able to reveal any information about x, so it is a part of a group of people with high
min-entropy is when it’s enough variable. If xd’s property isn’t present and we want to select one. Buy best psychiatrist email address lists online.
random number r with high min-entropy, and employ H(r | x)as the commitment, as we did in Chapter 1.

The idea behind this is that we release just x) as a hash H(r | x)at time T. Then at some time later we can show the rand x.Anybody is able to look through the append-only log and become certain that we have been aware of x at the time the data was published H(r | x),because there is no possible way to generate the data.

Uses of timestamping. What are the possibilities for this kind of time stamping that is secure? One possibility is to establish prior knowledge of an concept. Let’s say we want to prove that an idea we applied for a patent on was in our minds way earlier. This could be done through the publication of the design document or diagram when we first began thinking of the idea without telling anyone about the reason behind the idea. In the future, when we file for our patent, or when we announce the idea it is possible to release our original document and data and anyone could look back to confirm that we knew about it before we made the agreement to the idea. Buy best psychiatrist email address lists online.

It is also possible to show that another person has received an email we’ve sent them. Imagine that Alice employs Bob to do an assignment in programming The contract stipulates that Bob deliver his code to Alice at a specified date. Both parties wish to be sure that in the event of dispute in the future regarding the fact that Bob did the work or whether the code was performed according to the specifications, they can provide evidence of the work submitted and the date at which it was submitted. To do this the parties can decide to release the hash of Bob’s submitted work that is signed jointly by all parties. If one of them later lies about what they submitted , or the date it was submitted they are unable to show them wrong (say for instance, in an arbitration court) by disclosing the information that was used to create the hash. Buy best psychiatrist email address lists online.

Other interesting ideas can be constructed by using secure timestamps. There’s even a whole publicly-keyed signature method (called”the Guy Fawkes signature scheme) which merely uses the functions of hashing and also an append-only log. It doesn’t need any of the bulky cryptography used in signatures with public keys.

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Attacks on Proofs-of-“Clairvoyance”. One thing we aren’t able to do using secure timestamps alonehowever it would be wonderful to be able to do it be able to prove that clairvoyance can forecast the future. It’s plausible.

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It’s possible to release a promise to the details of an event set to happen (such as the outcome of a sports event or an electoral vote) and then, later, disclose that information to show that we knew the outcome prior to the time. What happens if this isn’t working?

In the latter part of 2014, in the final game during the final match of the World Cup, someone used this technique in order to “prove” that FIFA, the organization that hosts the World Cup, was corrupt. Following the conclusion of the match an unidentified Twitter account gained a lot of attention for tweeting about various instances that took place during the match, and timestamped prior to the moment the match began.For instance, it correctly posted that Germany were going to win in extra time, and that Mario Gotze would score. Buy best psychiatrist email leads online.

It appears that either the account’s owner Twitter account is able to predict the future, or that the game was fake. In reality, the account tweeted every possible outcome prior to the match began. For each player in the game the account tweeted a message that predicted that they would score. There were tweets for each possible final score of the game, and on and for the rest of (see figure 9.1). When the match was over all the fake predictions were removed which left the Twitter account with only real “predictions.”

The same type of attack can be used against any trusted timestamping device. It is as simple as committing to a range of outcomes and only disclose the agreements that prove to be valid. That means that if you do actually have the capability to forecast the future and desire to prove it you need to be able to prove that you have timestamps on the specific prediction rather than several predictions. If you’re publishing commitments based on hash it is difficult to accomplish Buy best psychiatrist email leads online.

This is the case especially in Bitcoin because our time stamping system is secure and does not connect commitments to any private identity of an individual. If you do not disclose your commitments, it’s simple to release a huge number of commitments, and those you do not reveal are unable to be identified back to the person who made them.

Time stamping securely the old-fashioned way. Here’s an easy, low-tech method to perform secure timestamping: release your hash in a newspaper or other medium that is seen by a large portion of people, and then purchase an advertisement. The archives of newspaper issues from the past are stored in libraries as well as on the internet. This gives you a high level of confidence that you had the information was in the newspaper on the day it was released. In the future, if you wish to disclose the information that you have committed, you could even make a new advertisement and publish the data to the newspaper in which you published the data. Buy best psychiatrist email leads online.

Secure timestamping with Bitcoin. If we want to make use of Bitcoin rather than newspapers to timestamp where do we place the hash committment? In the transaction? Or directly in the block?

The simplest method (and the one that people thought of first) is to instead of transferring cash to the haveh of the public key simply send funds to the haveh you’ve created in your personal data. The process “burns” those coins, and makes them ineligible for spending and therefore permanently lost, as you don’t have the private key that corresponds to the account. To reduce the cost you’ll need to transfer only a small amount like just one single satoshi (the minimum transaction value of Bitcoin).

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Although this strategy is easy to implement, the requirement to burn the coins is a drawback (although the amount of money burned will likely be small compared to the transaction costs).

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Another issue lies in the fact that Bitcoin miners do not have a way to tell if the output of a transaction is not able to be spent and therefore they have to track the transaction for a long time. The Bitcoin community has a negative opinion about this approach due to this reason.

A more sophisticated method known as CommitCoin permits you to encode your data to an encrypted private key. Remember that in Chapter 1 in which we stated: “With ECDSA, a reliable sources of randomness are crucial because a source of bad randomness could compromise your keys. It is logical to think that if you choose to use poor randomness to generate keys and the key you create will not be safe. However, it’s a flaw in ECDSA that even if you make use of poor randomness in the process of creating the signature, with your perfect key, this will also expose the private keys of yours.” Buy best psychiatrist email id database online.

CommitCoin utilizes this property. We create a new private key that encodes our commitment . Then we obtain its public key. We then send a tiny transaction (of maybe 10,000 satoshi) to the address and then return it in two pieces with a total of 1,000 satoshi. In addition, when sending it back, we employ the same randomness each time to sign the transaction. This allows anyone viewing the chain of blocks to calculate the secret key that is the one that contains the commitment, using two signatures.

As opposed to encoding your commitment into the key public, CommitCoin does not require you to burn coins , and allows miners to keep track of the unspendable output for a long time. It is however extremely complex. Buy best psychiatrist email id database online.

Unspendable outputs. In 2014, the best method to perform Bitcoin timestamping is to use an

OP_RETURN operation that results in an output that is not able to be spent. The OP_RETURN instruction immediately returns with an error, ensuring that the script will never be successfully executed and the information that you input is not considered. In Chapter 3 it could be used to prove burn, as well as to encode data of any kind. In 2015, OP_RETURN allows for 80 bytes of data transferred and will be more than sufficient to create an output from a hash functions (32 bytes for the SHA-256).

This technique prevents the accumulation of bloat in the output of unpaid transactions because miners trim the outputs of OP_RETURN. The cost of this commitment is basically the price in one fee per transaction. In 2014, the average transaction fee is just one cent. Buy best psychiatrist email id database online. The price can be cut further through the same commitment for multiple value. Since the end of 2014, there are several websites solutions that can help you with this. They gather a variety of commitments from various users and then combine them into a massive Merkle tree. They then publish an non-spendable output that contains the Merkle tree’s root. This is a promise to all the data users want to timestamp for the day.

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Illicit Content. One drawback of the ability to write random data into the chain of blocks, is users could abuse the feature. In the majority of nations, it is unlawful to distribute and/or possess certain types of content, such as child pornography. The penalties could be very severe. Copyright laws also limit the distribution of certain types of media.

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Certain enough, a number of people have attempted to do things similar in order to “grief” (i.e., to annoy or harass) members of the Bitcoin community. For instance, there’s been reports of pornographic links posted in Bitcoin’s Bitcoin block chain. The aim of these grievers are to render it unsafe to download the block chain to your hard drive and operate a full node because doing so could be a matter of storing and transmitting information which is prohibited. Buy best psychiatrist mailing id database online.

There’s no effective method to stop people from writing any kind of data to the block chain of bitcoin. One possible countermeasure is to only accept Pay-to-Script-Hashtransactions. This will make it slightly more costly to input random data however it wouldn’t hinder it from happening.

Thankfully the law isn’t an algorithm. It’s tempting at “hack” the law by techniques that can produce unintended or unintended results However, it isn’t an easy task. The law is intended to be read by humans, and they incorporate elements like intention. For instance, U.S. Code 2252, the part that is part of U.S. federal law that is pertaining to the possession, distribution and reception of child pornography. It employs the phrase “knowinglypossesses, or knowinglyaccesses with intent to view” when discussing prohibited activities (emphasis the word “knowingly” in our case). Buy best psychiatrist mailing id database online.

It’s also important to remember that, due to the limitations on size we mentioned earlier, data like images (except maybe tiny images) can’t be directly uploaded to the Bitcoin block chain. They’ll have to be hosted elsewhere or be written as links to the chain or encoded in a complex manner over multiple transactions. Additionally, the majority of Bitcoin clients don’t come with the capability to read and decode the data that’s written into transactions or even data encoded in multiple transactions.

Overlay Currencies. The positive aspect is that because we can write whatever data we like into Bitcoin We can also develop a brand new currency system based on Bitcoin without having to design an entirely different consensus method. We could simply utilize Bitcoin in the current state as an append-only log and then write all the information we require for our new system of currency straight to bitcoin’s Bitcoin blockchain. This is referred to as something we refer to as an “overlay currency”. Bitcoin is the primary basis, and the data of the currency overlay is written to Bitcoin’s Bitcoin block chain with unspendable transaction outputs. Buy best psychiatrist mailing id database online.

Naturally, Bitcoin mining companies will never be able to verify what you write into the block chain because they don’t understand (and do not care!) what data you input is valid according to the rules of the new currency. Everyone can put anything there , provided they take on the Bitcoin transaction costs. Instead, you’ll need to create more complex logic to validate transactions using the new currency and this logic has to be implemented in every client who is involved in the exchange or transfer of the currency.

For instance, in the case of an overlay currency, miners cannot refuse double spending. Instead, each user of the currency overlay must take a look at what’s written in the blockchain. In the event that an overlay transactions tries to spend an overlay currency that’s already spent this second transaction shouldn’t be considered. Because of this, there is no any such thing as a light SPV client for overlay currencies.

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Counterparty is an important overlaid currency. The majority of Counterparty transactions are recorded to Bitcoin’s Bitcoin Block Chain.

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In 2014, between 0.5 percent or 1% Bitcoin transactions included Counterparty information. Counterparty also has a more extensive and robust feature set than Bitcoin. It is a good idea to consider that Counterparty doesn’t need to come up with a new consensus algorithm and because Bitcoin miners don’t have to be aware of the Counterparty regulations, it are able to instead concentrate on creating interesting options like smart contracts, user-defined currencies, and much more. It is possible that the Counterparty API can be much bigger in scope than Bitcoin API because Bitcoin miners don’t have to know about it or be a part of it. Buy best psychiatrist mailing leads.

The prospect of creating a new currency that doesn’t require to establish an entirely new consensus system is attractive. There is no need to convince new miners to join your system. Moreover, you can even add new systems depend on Bitcoin (for instance they’re subject to the same requirements for fees like the other Bitcoin transactions. The method is also inefficientsince the nodes that are part of the cryptocurrency overlay might need to process lots of data, because Bitcoin nodes aren’t able to make th