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We can then think, “What did Satoshi know about the history of ecash?” To grasp this more clearly, we could begin by looking through what the author cites in his white paper and also the references on the earlier editions of the Bitcoin website. In his white paper, it cites a few documents on cryptography basics and probability theory. He also references the work in time-stamping that we have seen earlier and it’s only plausible to believe that he designed the structure of the chain being based on such sources because the similarities are obvious. He also mentions the Hashcash idea, which’s computational puzzle is quite similar to the one utilized in Bitcoin. There’s also the b-money reference. Then, on the website he made the references of Bitgold and also to an idea by Hal Finney for reusing computational puzzles. List of Investors lists

If we examine the emails exchanges made public by those who had correspondence with Satoshi Nakamoto during the beginning of the internet, we can see that the b-money idea was added later, as a result of the suggestions by Adam Back. Satoshi then sent an email to Wei Dai who created b-money and it appears that Dai was the person who advised him of Bitgold. This suggests that these ideas weren’t sources of inspiration for the original design. The designer later remained in contact in correspondence with Hal Finney, and that’s an excellent explanation of the reason he references Finney’s work on his website. email marketing database List of Investors

On the basis of this information, it is plausible that during the time of the creation of Bitcoin, Hashcash and time-stamping were the only items from the early days of ecash that Satoshi was aware of or believed were significant. Once he became aware of B-money and Bitgold However it appears that he recognized their importance. In the mid-2010 timeframe the Wikipedia article about Bitcoin was flagged as unworthy of deletion by Wikipedia’s editors based on their opinion that it was not interesting enough. The article was subject to debate between Satoshi and other people about the best way to write the article to ensure that Wikipedia would be able to accept the article. To this end, Satoshi suggested this description of Bitcoin: “Bitcoin is an implementation of Wei Dai’s b-money proposal on Cypherpunks in 1998 and Nick Szabo’s Bitgold proposal.” Thus, Satoshi at this point, was the positioning of Bitcoin as an expansion of these ideas or as an implementation of the two previous methods as a clear explanation of the way it works.

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But, what’s the deal with all the other things — the Chaumian E-Cash schemes as well as the credit card plans we examined? Did Satoshi be aware of any of that history while he was designing Bitcoin? It’s not clear. The man didn’t provide any evidence of having any knowledge about this background, but it’s possible that he didn’t refer to it since it wasn’t pertinent to Bitcoin. Bitcoin utilizes a totally different system of decentralization, and therefore there’s no reason to dwell on the old centralized systems that didn’t work. List of Investors email database providers

Satoshi himself is adamant about this by mentioning the Chaumian ecash in passing within one of his postings on in the Bitcoin forums. In a post about a different proposal, opencoin.org in his post, he mentions that they are “talking of the previous Chaumian central mint,” however, it could be because it was the only option accessible. Perhaps they’d like to explore a different direction. A lot of people dismiss the concept of e-currency in the same way as an unsalvageable cause due to the fact of the numerous companies that have had failed since the 90’s. It’s my hope that it was the centrally-controlled system that ruined them. It’s the first time we’ve attempted an untrust-based, decentralized system.” This will give us an idea of what Satoshi was thinking about the previous plans, and more specifically, what he thought about how Bitcoin is different. The fact that Bitcoin is decentralized is an important feature that sets it apart from the rest of the alternatives we’ve looked at. List of Investors lists

Another intriguing quote by Satoshi implies that he may perhaps not have the academic credentials. The majority of academic researchers brainstorm ideas and record them in a hurry, before they begin to build the systems. Satoshi claims that he used the his own strategy: “I actually did Bitcoin sort of reversed. Then I wrote the code first before I could be convinced that I would tackle every issue, and then I wrote the document. I am confident that I will be able to publish the code faster than I can write a complete specification.”

Because there’s a an element of mythology about Satoshi It’s worth noting that he did make mistakes just like all of us and wasn’t an accurate predictor that would be useful in the near future. There are flaws and design decisions that are questionable in the initial Bitcoin code, as and in its design. For instance it was possible of sending bitcoins to IP addresses, but it never caught up and, in the end it was a terrible idea. When he explained the benefits Bitcoin could be used for, his ideas were based on the notion of using it on the internet. This use case is fundamental to Bitcoin obviously but it’s not all there is. The vision he gave wasn’t of visiting the coffee shop and paying for your coffee using Bitcoin for instance. List of Investors lists

The last question we can consider, based on what we have learned from the past of digital currency is “Why does Satoshi maintain his anonymity?” There are a variety of motives. For one, it could be to play. A lot of people write their novels in anonymity and there are graffiti artists such as Banksy who remain anonymous. In the community Satoshi was a part of during that time as well as the Cypherpunk community as well as the Cryptography mailing list it was commonplace for anonymous users to write posts.

However there could be legal issues that influenced Satoshi’s decision. There were two U.S. companies, Liberty Reserve and e-Gold have been in legal troubles for laundering money. In 2006 one of the founding members of Liberty Reserve fled the United States because he was afraid that he’d be arrested for money laundering. The E-Gold founders on the other hand remain within the United States, and one was in fact arrested and agreed to plead guilty. The guilty plea was filed at the exact time Satoshi created his Bitcoin website and began sending emails to people with his idea. However, many people have created e-cash systems and no one else was afraid of the legal implications , or chose to keep their identity private. Therefore, while this could have been the cause, however it may not be the main motive. email marketing database List of Investors

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It’s also important to note that some features of ecash were patentable and that some members belonging to the Cypherpunk movement were worried regarding implementing ecash-based systems because of patents. Indeed, one message on the mailing list for Cypherpunks suggested that a group of anonymous coders use ecash to ensure that, if someone did suit, they wouldn’t be able to locate the coders. Although it’s difficult to believe that Bitcoin is in violation of the ecash patents due to how distinct its design and its underlying technology, it is possible that Satoshi was extra cautious. Maybe he was attracted by the concept that a coder was anonymous in the cypherpunk group. List of Investors email database providers

Another reason often mentioned is personal security. We’re aware that Satoshi has plenty of bitcoins he mined at the beginning of his career, and due to the success of Bitcoin, they have become a substantial amount of money. I believe this is an enticing reason. In the end, making a decision to remain anonymous isn’t something you do one time, it’s something is done on a continuous basis. However, it likely was not Satoshi’s primary motivation. When it was the first time Satoshi took on the name Satoshi Nakamoto, he had not published the whitepaper or the codebase that was used to create Bitcoin and it’s difficult to imagine Satoshi had any idea it would become as popular in the way it did. Actually, at several moments in the beginning of its history, Satoshi was optimistic but skeptical about the future of Bitcoin. He was aware that numerous previous efforts were unsuccessful and it was possible that Bitcoin could also fail. List of Investors quality email lists

Conclusion remarks

The growth of Bitcoin is quite impressive when you look at all the other ventures which failed to accomplish what it can do. Bitcoin is a notable innovation such as the block chain, and an uncentralized model that allows transactions between users. It offers a practical but not perfect level of privacy for the users. In Chapter 6, we’ll go over an in-depth look at privacy in Bitcoin. In one way, it’s weaker than the robust anonymity of DigiCash however in another way it’s more secure. This is because in DigiCash the only thing that was protected was the users who were sending the money who kept their identities private, it wasn’t the sellers. Bitcoin offers both senders and buyers (whether customers or merchants) the same degree of privacy.

Let me close with a few lessons that we can draw from Bitc List of Investors listsoin using the lenses of the other systems we’ve studied. First, don’t abandon a problem. Even if people have failed for 20 years when it came to developing digital money doesn’t mean that there’s no system in place that can work. The second thing is to be prepared to compromise. If you’re seeking absolute anonymity or a perfect decentralization, you’ll probably have to improve some of the areas you’ve designed. Bitcoin is, looking back appears to have made good choices. It reduces the anonymity of its users a bit, and demands that users be connected and online the peer-to-peer network. However, it turned out to be a good choice for users. purchase List of Investors email lists

One final point is that success is achieved by numbers. Bitcoin has been able to build an enthusiastic community of users and developers who were willing to contribute to this open source technology. This is a distinct approach to earlier attempts to create digital currency that were created by a corporation with the sole advocates to the system being people working for the firm. The current success of Bitcoin is due to the thriving community of supporters who promoted the technology, enlisted people to use it, and pushed merchants to accept it.

Introduction to Cryptography & Cryptocurrencies

Every currency requires a way to regulate supply and enforce different security features to stop

cheating. When it comes to fiat currencies organisations such as central banks manage the amount of money they have and then increase the amount of money available.

security features that prevent counterfeiting of physical currency. These security features make it harder for an attacker.

But they can’t make it unattainable to steal. In the end, law enforcement is crucial to protect

stopping people from violating regulations of our system. List of Investors consumer email database

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Additionally, cryptocurrencies must be protected by security measures to prevent users from altering the state of the system, or from equivocating. That is, giving contradicting statements to various people. If Alice claims to Bob that she has paid him a digital currency for instance she shouldn’t be in a position to convince Carol that she actually paid the same amount. However, unlike fiat currencies the security requirements of cryptocurrencies must be enforced solely technologically and without the need for an authority central to the system. List of Investors email database providers

The word “cryptography” means that cryptocurrency makes usage of cryptography. Cryptography is a method of securely coding the principles of a cryptocurrency system within the system itself. It can be used to stop tampering and equivocation and also to encode the rules of the creating new units of currency into a mathematical process. To fully comprehend the cryptocurrencies, we’ll need to understand the cryptographic principles they are based on.

The field of cryptography is an extensive academic field that employs a variety of sophisticated mathematical techniques which are notoriously nebulous and hard to grasp. However, Bitcoin does not rely on the use of a few simple and well-known cryptographic structures. This chapter will examine cryptographic hashes as well as digital signatures, two fundamentals which prove efficient in creating cryptographic currencies. The next chapters will cover more complex cryptographic schemes, like zero-knowledge proofs which are utilized in the proposed extensions and changes to Bitcoin.

When we’ve taken in the important cryptographic natives, we’ll examine a portion of the manners by which those are utilized to fabricate digital currencies. We’ll finish this section for certain instances of basic digital currencies that outline a portion of the plan difficulties that we really want to manage. purchase List of Investors email lists

Cryptographic Hash Functions

A cryptographic hash function is the first cryptographic primitive we need to understand. It is a mathematical function that has three properties.

It can input any string of any length. List of Investors lists

It produces an output of fixed size. We will assume that the output size is 256 bits to make the discussion concrete. Our discussion is valid for any output size, as long as it’s sufficient.

It is efficient computable. This means that you can find the output of the hash function for any input string in a reasonable time. Technically speaking, the time required to compute an n-bit string’s hash should be O(n).

These properties are a general hash function that can be used to create a data structure, such as a hashtable. We will be focusing exclusively on cryptographichash function. For a hash function to be cryptographically secure, we’re going to require that it has the following three additional properties: (1) collision-resistance, (2) hiding, (3) puzzle-friendliness.

To understand why it is useful to have a function behave this way, we will examine each property more closely. A cryptography student should be aware of the differences in how this book treats hash functions. Although puzzle-friendliness is not required for cryptographic hash function, it will prove useful for cryptocurrency. purchase List of Investors email lists

Property 1: Collision-resistance.The first property that we need from a cryptographic hash function is that it’s collision-resistant. When two inputs produce the exact same output, a collision is occurring. A hash function H (.) iscollision-resistant if nobody can find a collision. Formally:

Collision-resistance: Ahash functionHis said to be collision resistant if it is infeasible to findtwo values, xand y,such that xy,yet H(x)=H(y).

Although we stated that nobody could find a collision, we didn’t say that there aren’t any collisions. We know that collisions exist and can prove it with a simple counting argument. The input space for the hash function includes all strings of any length, while the output space only contains strings of a fixed length. The input space is larger that the output space, and the input space can be infinite while the output spaces are finite, so there must be input strings which map to the same output string. According to the Pigeonhole Principle, there will always be many inputs that map directly to an output.

If we randomly select 2 + 1, there is a 99.8% chance of at least two of them colliding. We can only examine the square root of the possible outputs to find a collision. This is a phenomenon of probability called the birthday paradox. List of Investors consumer email database

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This is a very general, but not practical, algorithm for finding collisions for any hash function. The more difficult question is, is there another method that can be used to locate a collision for a specific hash function? The generic collision detection algorithm may not be practical to use, but there might be another algorithm that can find a collision for a particular hash function. List of Investors address lists

Application: Message digests. Now that we understand collision-resistance, the next question is: What does collision-resistance serve? Let’s look at one example: If two inputs x and yto a collision resistant hash function Hare are different, it is safe to assume their hashes H (x)and H (y)are different. However, if they knew an xand an ythat were both different but shared the same hash, this would contradict our assumption that His collision resistance.

This argument allows us use hash outputs to create message digests. SecureBox is an online file storage system that authenticates users and allows them to upload files. Let’s say Alice uploads a large file and wants to verify that it is the same file that she uploaded. You can do this by saving the entire file locally and comparing it with the one she downloaded. Although this is possible, it defeats the purpose behind uploading it. Alice can use the local copy if she needs access to the file to verify its integrity. buy List of Investors targeted email list

This problem can be solved elegantly and efficiently by using collision-free hashes. Alice only needs to know the hash of her original file. She later downloads the file from SecureBox and computes the hash. Then she compares it with the one she had previously saved. If they match, she can confirm that it is the file she uploaded. However, if the hashes differ, Alice can conclude that it was altered. Remembering the hash thus allows her to detect accidentalcorruption of the file during transmission or on SecureBox’s servers, but also intentionalmodification of the file by the server. These guarantees are essential to cryptography’s ability to detect malicious behavior from other entities. List of Investors lists

The hash is a fixed-length digest or unambiguous summary of a message. This allows us to quickly recall things we have seen and help us recognize them again. The entire file could have been gigabytes in size, but the hash has a fixed length of 256 bits for our hash function. This significantly reduces the storage requirements. We’ll be discussing applications where a hash can be useful as a message digest later in this chapter.

Property 2: Hiding This property cannot be true in its stated form. Let’s take an example. We will flip a coin. If the result of the coin flip was head, we will announce the hash string “heads”. If the result of the coin flip was heads, we’ll announce the hash for the string “heads”.

Then, we ask an adversary (who didn’t see this coin flip but saw the hash output) to determine the string that was hashed. We’ll soon understand why this game is so popular. They would then simply compute the hash for the string “heads” as well as the hash for the string “tails” to see which one was given. In just a few steps they can determine what the input was. buy List of Investors targeted email list

Because there were only two possible values for x, the adversary was able guess the string. It was also easy to try both. To be able achieve the hiding property, it must be clear that there is no value of x which is especially likely. This means that xmust be selected from a set that is in some way very distributed. This method of trying to find a few likely values of x will not work if xis selected from such a set.

The big question is, can we attain the hiding property if the values we desire are not from a spread-out group like in our “heads” and “tails” experiments? The answer is yes, Perhaps we can conceal an input that isn’t spread out by concatenating with another input that has been spread out.

Information-theory uses min-entropy to measure how predictable an outcome is.

Min-entropy refers to the intuition that the distribution (i.e. random variable) is extremely spread out. This means that we can’t sample from the distribution and find any particular value.

It’s very likely that it will happen. For example, let’s say that ris is chosen uniformly among all the strings. List of Investors consumer email database

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If the length of a string is 256 bits, it was selected with probability 1/2, which is an infinisimally small value.

Application: Commitments. Now let’s examine an application of hiding property. We are referring to a “commitment” in particular. This is the digital equivalent of taking a value and sealing it in an envelope. Then, we will examine how to apply the hiding property. You have committed to the contents of the envelope by doing this. You haven’t yet opened the envelope, so even though it’s your commitment to a certain value, it remains secret from others. You can later open the envelope to reveal the value you have committed to. List of Investors address lists

First, generate a random nuce to use in a commitment scheme. The commit function is then applied to the nonce along with msg (the value being committed too), and the commitment com is published. This stage is similar to putting the sealed envelope on a table. If we wish to reveal the value they have committed to previously, we will publish the random nonce we used to create the commitment and the message,msg. Now, anyone can verify that msg was the message that was committed to earlier. This is similar to opening the envelope.

to the contents of the envelope. It’s impossible to find two messages. You can’t commit to one message and later claim you have committed to the other. buy List of Investors targeted email list

How do we determine if these properties are true? Before we can answer that question, we must discuss how we will actually implement a commitment program. This can be done using a cryptographic haveh function. Take a look at the following commitment scheme.

To commit to a message we generate a random nonce of 256 bits. Next, we combine the nonce with the message to generate a hash and return the commited value. Someone will then compute the same hash of nonce that they received concatenated to the message. They will also check if that is equal to the commitment they saw. List of Investors lists

Let’s take a look at the properties we need for our commitment schemes.

The commitments hiding property is precisely what we needed for our hash functions. If key was chosen randomly as a 256-bit value, then the hiding property states that it is impossible to recover the message from hash output if we hash keyand the message. It turns out that the binding property can be implimented by1 the collision-resistant property in the underlying hash functions. buy List of Investors database for marketing

This means that if He has a collision-resistant and hiding hash function, the commitment scheme will work in that it will have all the security properties.

Property 3: Puzzle friendliness. We will need the third security property from hash functions to be puzzle-friendly. This property is quite complex. First, we will explain the technical requirements for this property and then provide an application to show why this property is so useful.

This means that it is very difficult to find another value to match the target if the input is selected in a random way.

Application: Search puzzle. Now let’s look at an application that illustrates this property’s usefulness. This application will build a search puzzle. It is a mathematical problem that requires us to search a large space to find the answer. A search puzzle is not easy to solve. This means that there is no other way to find the solution than by searching large spaces. The opposite is not true. List of Investors lists

Search puzzle. Search puzzles consist of List of Investors email database free

A value, id (which we refer to as the puzzle-ID), is a value that was chosen from a high min entropy distribution

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This intuition states that H can accept any 2nvalues if it has an output of n bits. The input must be found so that the output falls within Y. This set is usually much smaller than all other outputs. How difficult the puzzle is will depend on how large Y is. The puzzle will be trivial if it has all the n-bit strings, but the one element puzzle will be the most difficult. There are no shortcuts because the puzzle ID has high min-entropy. However, cheating could be done if the ID had a certain value. For example, pre-computed solutions to the puzzle using that ID. List of Investors address lists

Puzzle-friendly means that a search puzzle can be solved in any way that is possible. This is true even if the puzzle-IDs are generated in an appropriately random manner. This idea will be used later in our discussion about Bitcoin mining.

SHA-256. We have discussed three properties and one application for hash functions. Let’s now discuss one particular hash function we will use in this book. There are many hash functions, but this one is the most popular and widely used. It is called SHA-256. buy List of Investors database for marketing

Remember that our hash functions must work with inputs of an arbitrary length. As long as we are able to build a hash functions that work on inputs of fixed length, there is a generic way to make it work on inputs of arbitrary length. This is the Merkle-Damgard transformation. This method is used by SHA-256, which is just one of many commonly-used hash functions. Common terminology refers to the compression function, which is a fixed-length collision-resistant hash functions. It has been shown that the overall hash function will also be collision resistant if it is collision-resistant.

It is very simple to use the Merkle-Damgard transformation. The Merkle-Damgard transform is very simple. The input length of the compression function will be (m-n+ n=m). We use an Initialization Vector instead for the first block. This number is used every time the hash function is called. In practice, you can simply look it up in a standard document. You return the output of the last block.

SHA-256 uses a compression algorithm that accepts 768-bit inputs and produces 256-bit outputs. Block size is 512 bits. For a graphic representation of how SHA-256 works, see Figure 1.3. buy List of Investors database for marketing

We have already discussed cryptographic hash function, hash functions that are cryptographic functions with special properties and their applications. Now we will discuss a particular hash function that is used in Bitcoin. We’ll be discussing how to use hash functions in order to create more complex data structures for distributed systems such as Bitcoin.

Sidebar: Modeling hash functions. Hash functions are the Swiss Army Knife of cryptography. They can be used in an amazing variety of applications. This versatility also means that different applications will require different properties for hash functions in order to guarantee security. It is notoriously difficult to identify the properties of hash functions that will provide provable security for all applications. List of Investors lists

We’ve chosen three properties that are critical to how hash functions work in Bitcoin and other cryptocurrency. These properties may not be necessary for all uses of hash functions. As we’ll see, Bitcoin mining is not the only area where puzzle-friendliness can be important.

Secure systems designers often give up and create model hash functions, functions that produce an independent random value for each input. Cryptography is still a controversial area. It doesn’t matter what your position is on the issue, it is important to think about ways to decrease the security properties we want in our applications. This can be useful intellectual exercise for building secure system. This chapter is intended to teach you this skill. List of Investors email database free

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This section will discuss hash pointsers and their applications. A hash pointer can be a data structure that is useful in many of these systems. A hash pointer simply points to the location of information, along with a cryptographic hash. A regular pointer allows you to retrieve the information. However, a hash-pointer can also be used to verify that the information has not changed. List of Investors database for sale

You can create all sorts of data structures using hash pointers. We can intuitively take a data structure such as a binary search tree or linked list and use hash pointers to implement it.

Block chain. In Figure 1.5, we created a linked list with hash pointers. This data structure will be called a block-chain. Unlike a regular linked listing that has a series blocks, each block contains data and a pointer at the previous block. In a block-chain, the block pointer to the block before it is deleted will be replaced by a hash key. Each block contains not only the value of the block before it, but also a digest that shows us the current value. This allows us to confirm that the value hasn’t changed. The head of the list is simply a regular hash-pointer that points at the most recent data block.

One use case for a blockchain is a tamper evident log. This means that we want to create a log data structure which stores lots of data and allows us add data to the log. We will detect if someone alters the data in the log. List of Investors database for sale

Let’s look at what happens when an adversary tries to alter data in the middle of a block chain. This will help us understand why block chains have this tamper evident property. The adversary wants to do this in a way that anyone who only knows the hash pointer at block chain’s head won’t be able detect the tampering. The adversary alters the data in block k. This means that the block k+1 hash, which is a hash for the entire block, will not match up. Because the hash function is non-coincidence resistant, statistically we can guarantee that the new hash won’t match the altered content. So we can detect inconsistencies between the block k data and the block k+1 hash pointer. The adversary could continue trying to cover this up by changing the hash of the next block. This strategy can be continued by the adversary, but it will not work once he reaches top of the list. The adversary can’t change any block as long as the hash pointer is stored at the top of the list. List of Investors lists

This means that the adversary will have to alter the hash pointers back to the beginning if he wants to tamper any data in the entire chain. He won’t have the ability to alter the head of the list, so he will eventually run into a roadblock. It turns out that just by remembering one hash pointer, all we have is a tamper evident hash of the entire list. This block chain can be used to build as many blocks as you want. We will refer back to the genesis block, which is the block at the start of the list.

It may be obvious that block chain construction looks very similar to Merkle-Damgard construction, which we discussed in the previous section. They are very similar and both have the same security argument. List of Investors email database free