Incorporating fairness protocol in ch1

01_introduction.asciidoc

@@ -2,49 +2,150 @@
 [[intro_what_is_the_lightning_network]]
 == Introduction
 
-Welcome to Mastering the Lightning Network!
+Welcome to _Mastering the Lightning Network_!
 
 The Lightning Network is a protocol for using Bitcoin in a smart and non-obvious way.
 It is a second layer technology on top of Bitcoin.
-The Lightning Network, abbreviated with LN, is changing the way people exchange value online and it's one of the most exciting advancements to happen in Bitcoin's history.
-Today, in 2020, the Lightning Network is in its infancy.
+The Lightning Network, often abbreviated as "LN", is changing the way people exchange value online and it's one of the most exciting advancements to happen in Bitcoin's history.
+Today, in 2020, the Lightning Network is still in its infancy.
 In concept it was first proposed in 2015 and the first implementation was launched in 2018.
 As of 2020, we're only beginning to see the opportunities the Lightning Network provides including improved privacy, speed, and scale.
-With core knowledge of the Lightning Network, you can help shape the future of the network while building opportunities for yourself as well.
-Some basic knowledge about Bitcoin is assumed but can be readily acquired by reading the first two chapters of _Mastering Bitcoin_ which are available for free online.
+With core knowledge of the Lightning Network, you can help shape the future of the network while also building opportunities for yourself.
+Some basic knowledge about Bitcoin is assumed but can be readily acquired by reading _Mastering Bitcoin_, available for free online. We also cover the most important Bitcoin concepts, you need must know to study the Lightning Network, in <<bitcoin_fundamentals>>.
 
-While the bulk of this book is written for programmers, the first two chapters are written to be approachable by anyone regardless of technical experience. In order to better understand how the technology actually works, and why people use it, we'll be following a number of users and their stories. But first, we'll introduce some of the key concepts in the Lightning Network. Let's get started with why the Lightning Network was proposed in the first place.
+While the bulk of this book is written for programmers, the first few chapters are written to be approachable by anyone regardless of technical experience.
 
-=== Motivation for the Lightning Network
+=== Trust in decentralized networks
 
-As Bitcoin and the demand for transactions grows, the number of transactions in each block will increase until it eventually hits the block size limit.
-When blocks are full, excess transactions are left to wait in a queue.
-Many users will increase the fees they're willing to pay in order to buy space for their transactions in the next block.
-At the same time, an increasing number of users are left behind.
-Their transactions, e.g. microtransactions such as common small spendings, are not economically qualified to be on the network.
-We could increase the block size to create space for these smaller transactions.
-However, increasing block size simply shifts the problem to node operators, and requires them to expend resources to facilitate these additional transactions.
+You will often hear people calling Bitcoin and the Lightning Network "trustless". At first glance this is confusing. After all, isn't trust a good thing? Banks even use it in their names! Isn't a "trustless" system a system devoid of trust a bad thing?
 
-Because blockchains are gossip protocols, each node is required to know and validate every single transaction that occurs on the network. Furthermore, once validated, each transaction and block must be propagated to the node's "neighbors", multiplying the bandwidth requirements. As such, the greater the block size, the greater the bandwidth, processing, and storage requirements for each individual node, effectively limiting the amount of scaling that can be done this way. Furthermore, scaling in this fashion has an undesirable side effect of centralizing the network by reducing the number of nodes and node operators. Since node operators are not compensated for running nodes, if nodes are very expensive to run, only a few well funded node operators will continue to run nodes.
+The use of the the word "trustless" is intended to convey the ability to operate without _needing_ trust in the other participants in the system. In a decentralized system like Bitcoin you can always choose to transact with someone you trust. However, the system ensures you can't be cheated even if you can't trust the other party in a transaction. Trust is a nice-to-have instead of a must-have property of the system.
+
+Contrast that to the traditional banking system where you _must_ place your trust in a third party, since they control your money. If they violate that trust you may be able to find recourse in a regulator or court, but you would be facing an enormous power imbalance.
+
+Trustless does not mean devoid of trust. It means that trust is not a necessary prerequisite to all transactions and that you can transact even with people you don't trust because the system prevents cheating.
+
+Before we get started with the Lightning Network, we need to understand the basic concept that underlies Bitcoin, the Lightning Network and many other such systems:
+
+_Achieving fair outcomes between participants, who do not need to trust each other, without the need for a central authority_
+
+We call this important concept a _fairness protocol_ and both Bitcoin and the Lightning Network are examples of fairness protocols.
+
+=== Fairness without central authority
+
+When people have competing interests, how can they establish enough trust to engage in some cooperative or transactional behavior? The answer to this question lies at the core of several scientific and humanistic disciplines, such as economics, sociology, behavioral psychology, and mathematics. Some of those disciplines give us "soft" answers, that depend on concepts such as reputation, fairness, morality, even religion. Other disciplines give us concrete answers that depend only on the assumption that the participants in these interactions will act rationally.
+
+In broad terms there are a handful of ways to ensure fair outcomes in interactions between individuals who may have competing interests:
+
+* Require trust - you only interact with people who you already trust, due to prior interactions, reputation, or familial relationships. This works well enough at small scale, especially within families and small groups, that it is the most common basis for cooperative behavior. Unfortunately, it doesn't scale and it suffers from tribalist (in-group) bias.
+
+* Rule of law - establish rules for interactions that are enforced by an institution. This scales better, but it cannot scale globally due to differences in customs and traditions, as well as the inability to scale the institutions of enforcement. Nasty side-effect: the institutions become more and more powerful as they get bigger and that leads to corruption.
+
+* Trusted third parties - put an intermediary in every interaction to enforce fairness. Combined with the "rule of law" to provide oversight of intermediaries, this scales better, but suffers from the same imbalance of power: the intermediaries get very powerful and attract corruption. Concentration of power leads to systemic risk and systemic failure ("Too big to fail").
+
+* Game theoretical fairness protocols - this last category emerges from the combination of the internet and cryptography and is the subject of this section. Let's see how it works and what its advantages and disadvantages are.
+
+==== Trusted protocols without intermediaries
+
+Cryptographic systems like Bitcoin and the Lightning Network are systems that allow you to transact with people (and computers) that you don't trust. This is often referred to as "trustless" operation, even though it is not actually trustless. You have to trust in the software that you run and you have to trust that the protocol implemented by that software will result in fair outcomes.
+
+The big distinction between a cryptographic system like this and a traditional financial system, is that in traditional finance you have a _trusted third party_, for example a bank, to ensure that outcomes are fair. A significant problem with such systems is that they give too much power to the third party and they are also vulnerable to a _single point of failure_. If the trusted third party itself violates trust or attempts to cheat, the basis of trust breaks.
+
+As you study cryptographic systems, you will notice a certain pattern: instead of relying on a trusted third party, these systems attempt to prevent unfair outcomes by using a system of incentives and disincentives. In cryptographic systems you place trust in the _protocol_, which is effectively a system with a set of rules that, if properly designed, will correctly apply the desired incentives and disincentives. The advantage of this approach is two fold. Not only do you avoid trusting a third party, you also reduce the need to enforce fair outcomes. So long as the participants follow the agreed protocol and stay within the system, the incentive mechanism in that protocol achieves fair outcomes without enforcement.
+
+The use of incentives and disincentives to achieve fair outcomes is one aspect of a branch of mathematics called _game theory_, which studies "models of strategic interaction among rational decision makers" footnote:[Wikipedia "Game Theory": https://en.wikipedia.org/wiki/Game_theory]. Cryptographic systems that control financial interactions between participants, such as Bitcoin and the Lightning Network rely heavily on game theory to prevent participants from cheating and allow participants who don't trust each other to achieve fair outcomes.
+
+While game theory and its use in cryptographic systems may appear confounding and unfamiliar at first, chances are you're already familiar with these systems in your everyday life, you just don't recognize them yet. Below we'll use a simple example from childhood to help us identify the basic pattern. Once you understand the basic pattern you will see it everywhere in the blockchain space and you will come to recognize it quickly and intuitively.
+
+In this book, we call this pattern a _Fairness Protocol_ defined as a process that uses a system of incentives and/or disincentives to ensure fair outcomes for participants who don't trust each other. Enforcement of a fairness protocol is only necessary to ensure that the participants can't escape the incentives or disincentives.
+
+==== A fairness protocol in action
+
+Let's look at an example of a fairness protocol, which may be familiar to any reader, perhaps as a memory from their childhood.
+
+Imagine a family lunch, with a parent and two children. The parent has prepared a bowl of fried potatoes ("french fries" or "chips" depending on which English dialect you use). The two siblings must share the plate of chips. The parent must ensure a fair distribution of chips to each child, otherwise the parent will have to hear constant complaining (maybe all day) and there's always a possibility of the unfair situation escalating to violence. What is a parent to do?
 
 [NOTE]
 ====
+Any similarity between the scenario above and Andreas' childhood experiences with his two cousins is entirely coincidental and should not be mentioned again. The battles of the french fries created enough drama and should be left in the past.
+====
+
+There are a few different ways that fairness can be achieved in this strategic interaction between two siblings that do not trust each other and have competing interests. The naive but commonly used method is for the parent to use their authority as a trusted third party: they split the bowl of chips into two servings. This is similar to traditional finance, where a bank, accountant or lawyer acts as a trusted third party to prevent any cheating between two parties who want to transact.
+
+The problem with this scenario is that this puts a lot of power in the hands of the trusted third party. The parent is accused of playing favorites and not sharing the chips equally. The siblings may fight over the chips, dragging the parent into their fight. Eventually the parent threatens to never again cook french fries if it always results in fights. It is an empty threat, and so the cycle repeats daily.
+
+But a much better solution exists: the siblings are taught to play a game called "split and choose". At each lunch one sibling splits the bowl of chips into two servings and the *other* sibling gets to choose which serving they want. Almost immediately, the siblings figure out the dynamic of this game. If the one splitting makes a mistake or tries to cheat, the other sibling can "punish" them by choosing the bigger bowl. It is in the best interest of both siblings, but especially the one splitting the bowl, to play fair. Only the cheater loses in this scenario. The parent doesn't even have to use their authority or enforce fairness. All the parent has to do is _enforce the protocol_; as long as the siblings cannot escape their assigned roles of "splitter" and "chooser", the protocol itself ensures a fair outcome without the need for any intervention. The parent can't play favorites or distort the outcome.
+
+==== Security primitives as building blocks
+
+In order for a fairness protocol like this to work, there need to be certain guarantees, or _security primitives_ that can be combined to ensure enforcement. The first security primitive is _strict time ordering/sequencing_: the "splitting" action must happen before the "choosing" action. It's not immediately obvious, but unless you can guarantee that action A happens before action B, then the protocol falls apart. The second security primitive is _commitment with non-repudiation_. Each sibling must commit to their choice of role: either splitter or chooser. Also, once the splitting has been completed, the splitter is committed to the split they created - they cannot repudiate that choice and go try again.
+
+Cryptographic systems offer a number of security primitives that can be combined in different ways to construct a fairness protocol. In addition to sequencing and commitment, we can also use many other tools:
+
+- Hash functions to fingerprint data, as a form of commitment, or as the basis for a digital signature.
+- Digital signatures for authentication, non-repudiation, and proof of ownership of a secret.
+- Encryption/decryption to restrict access to information to authorized participants only.
+
+This is only a small list of a whole "menagerie" of security and cryptographic primitives that are in use. More basic primitives and combinations are invented all the time.
+
+In our real-life example, we saw one form of fairness protocol called "split and choose". This is just one of a myriad different fairness protocols that can be built by combining the building blocks of security primitives in different ways. But the basic pattern is always the same: two or more participants interact without trusting each other, by engaging in a series of steps that are part of an agreed protocol. The protocol's steps arrange incentives and disincentives to ensure that if the participants are rational, cheating is counter-productive and fairness is the automatic outcome. Enforcement is not necessary to get fair outcomes - it is only necessary to keep the participants from breaking out of the agreed protocol.
+
+Now that you understand this basic pattern, you will start seeing it everywhere in Bitcoin, the Lightning Network and many other systems. Let's look at some specific examples, next.
+
+==== Example of the fairness protocol
+
+The most prominent example of a "fairness protocol", is Bitcoin's consensus algorithm _Proof of Work_ (PoW). In Bitcoin, miners compete to verify transactions and aggregate them in blocks. To ensure that the miners do not cheat, without entrusting them with authority, Bitcoin uses a system of incentives and disincentives. Miners have to use a lot of electricity doing "work", that is embedded as a "proof" inside every block. This is achieved because of a property of hash functions where the output value is randomly distributed across the entire range of possible outputs. If miners succeed in producing a valid block fast enough, they are rewarded by earning the block reward for that block.  Forcing miners to use a lot of electricity before the network considers their blocks means that they have an incentive to correctly validate the transactions in the block. If they cheat or make any kind of mistake, their block is rejected and the electricity they used to "prove" it is wasted. No one needs to force miners to produce valid blocks, the reward and punishment incentivize them to do so. All the protocol needs to do is ensure that only valid blocks with proof of work are accepted.
+
+The "fairness protocol" pattern can also be found in many different aspects of the Lightning Network:
+
+* Those who fund channels make sure that they have a refund transaction signed before they publish the funding transaction.
+
+* Whenever a channel is moved to a new state, the old state is "revoked" by ensuring that if anyone tries to broadcast it, they lose the entire balance and get punished.
+
+* Those who forward payments know that if they commit funds forward, they can either get a refund or they get paid by the node preceding them.
+
+Again and again, we see this pattern. Fair outcomes are not enforced by any authority. They emerge as the natural consequence of a protocol that rewards fairness and punishes cheating. A fairness protocol that harnesses self-interest by directing it towards fair outcomes.
+
+Bitcoin and the Lightning Network are both implementations of fairness protocols. So why do we need the Lightning Network? Isn't Bitcoin enough?
+
+=== Motivation for the Lightning Network
+
+Bitcoin is a system that records transactions on a globally replicated public ledger. Every transaction is seen, validated and stored by every participating computer. As you can imagine, this generates a lot of data and is difficult to scale.
+
+As Bitcoin and the demand for transactions grew, the number of transactions in each block increased until it eventually reached the block size limit.
+Once blocks are "full", excess transactions are left to wait in a queue.
+Many users will increase the fees they're willing to pay in order to buy space for their transactions in the next block.
+
+If demand continues to outpace the capacity of the network, an increasing number of user's transactions are left waiting unconfirmed. Competition for fees also increases the cost of each transaction, making many smaller-value transactions (e.g. micro-transactions) completely uneconomical during these periods of high demand.
+
+To solve this problem, we could increase the block size limit to create space for more transactions. An increase in the "supply" of block space will lead to a lower price equilibrium for transaction fees.
+
+However, increasing block size shifts the cost to node operators, and requires them to expend more resources to validate and store the blockchain.  Because blockchains are gossip protocols, each node is required to know and validate every single transaction that occurs on the network. Furthermore, once validated, each transaction and block must be propagated to the node's "neighbors", multiplying the bandwidth requirements. As such, the greater the block size, the greater the bandwidth, processing, and storage requirements for each individual node. Increasing transaction capacity in this way has the undesirable effect of centralizing the system by reducing the number of nodes and node operators. Since node operators are not compensated for running nodes, if nodes are very expensive to run, only a few well funded node operators will continue to run nodes.
+
+.Scaling Blockchains
+****
 The side effects of increasing the block size or decreasing the block time with respect to centralization of the network are severe as a few calculations with the numbers show.
 Let us assume the usage of Bitcoin grows so that the network has to process 40,000 transactions per second.
 Assuming 250 Bytes on average per transaction this would result in a data stream of 10 Megabyte per second or 80 Mbit/s just to be able to receive all the transactions.
 This does not include the traffic overhead of forwarding the transaction information to other peers.
+While 10 MB/s does not seem extreme in the context of high-speed fiber optic and 5G mobile speeds, it would effectively exclude anyone who cannot meet this requirement from running a node, especially in countries where high-performance internet is not affordable or widely available.
 
-While 10 MB/s does not seem extreme in the context of high-speed fibre and 5G mobile speeds, it would effectively exclude anyone who cannot meet this requirement from running a node, especially in countries where high-performance internet is not affordable or widely available.
 Users also have many other demands on their bandwidth and cannot be expected to expend this much only to receive transactions.
-Furthermore storing this information locally would result in 864,000 Megabytes per day. This is roughly one Terabyte of data or the size of a hard drive.
-While verifying 40,000 ECDSA signatures per second seems barely feasible (c.f.: https://bitcoin.stackexchange.com/questions/95339/how-many-bitcoin-transactions-can-be-verified-per-second) nodes could hardly catch up initial sync of the blockchain.
-====
+Furthermore storing this information locally would result in 864GB Megabytes per day. This is roughly one Terabyte of data or the size of a hard drive.
+
+Verifying 40,000 ECDSA signatures per second is also barely feasible (c.f.: https://bitcoin.stackexchange.com/questions/95339/how-many-bitcoin-transactions-can-be-verified-per-second) making the _Initial Blockchain Download (IBD)_ of the Bitcoin blockchain  (synchronizing and verifying everything starting from the genesis block) almost impossible without very expensive hardware.
+
+While 40,000 transactions per second seems like a lot it only achieves parity with traditional financial payment networks at peak times. Innovations in machine-to-machine payments, micro-transactions and other applications are likely to push demand to many orders higher than that.
+
+Simply put: You can't scale a blockchain to validate the entire world's transactions in a decentralized way.
+****
 
 But what if each node wasn't required to know and validate every single transaction? What if there was a way to have scalable off-chain transactions, without losing the security of the Bitcoin network?
 
 In February 2015, Joseph Poon and Thaddeus Dryja proposed a possible solution to the Bitcoin Scalability Problem, with the publication of _"The Bitcoin Lightning Network: Scalable Off-Chain Instant Payments"_
 footnote:[Joseph Poon, Thaddeus Dryja - "The Bitcoin Lightning Network: Scalable Off-Chain Instant Payments" (https://lightning.network/lightning-network-paper.pdf).]
-In the now outdated whitepaper, Poon and Dryja estimate that in order for Bitcoin to reach the 47,000 transactions per second processed at peak by Visa, it would require 8 GB blocks.
+
+In the (now outdated) whitepaper, Poon and Dryja estimate that in order for Bitcoin to reach the 47,000 transactions per second processed at peak by Visa, it would require 8 GB blocks.
 This would make running a node completely untenable for anyone but large scale enterprises and industrial grade operations.
 The result would be a network in which only a few users can actually validate the state of the ledger.
 Bitcoin relies on users validating the ledger for themselves, without explicitly trusting third parties, in order to stay decentralized.
@@ -56,13 +157,13 @@ They will only make use of the Bitcoin blockchain in order to load bitcoin onto
 The result is that many more Bitcoin payments can take place "off-chain", with only the initial loading and final settlement transactions needing to be validated and stored by Bitcoin nodes.
 Aside from reducing the burden on nodes, payments on the Lightning Network will be cheaper for users as they do not need to pay blockchain fees, and more private for users as they are not published to all participants of the network and furthermore not stored permanently.
 
-While the Lightning Network was initially conceived for Bitcoin, it can be implemented on any blockchain that meets its technical requirements.
+While the Lightning Network was initially conceived for Bitcoin, it can be implemented on any blockchain that meets some basic technical requirements. Other blockchains, such as Litecoin, already support the Lightning Network. Additionally, several other blockchains are developing similar "second layer" or "layer 2" solutions to help them scale.
 
 === Lightning Network Basic Concepts
 
 As we start exploring the Lightning Network, we will encounter some technical terminology that might, at first, be confusing and a bit difficult to understand. While all of these concepts and terms will be explained in detail as we progress through the book, and are defined in the glossary, we need some basic clarifications to get started. Here are some of the concepts you will encounter in the first two chapters of this book:
 
-Node:: A computer that participates in a network. A Lightning node is a computer that participates in the Lightning Network. A Bitcoin node is a computer that participates in the Bitcoin Network. Typically a Lightning Network user will run a Lightning node and a Bitcoin node.
+Node:: A computer that participates in a network. A Lightning node is a computer that participates in the Lightning Network. A Bitcoin node is a computer that participates in the Bitcoin Network. Typically a Lightning Network user will run a Lightning node _and_ a Bitcoin node.
 
 Blockchain:: A distributed transaction ledger, produced by a network of computers. Bitcoin, for example, is a system that produces a blockchain. The Lightning Network is not itself a blockchain, nor does it produce a blockchain. It is a network that relies on an existing external blockchain for its security.
 
@@ -83,7 +184,7 @@ More detailed definitions of these and many other terms can be found in the <<gl
 Throughout this book, you will see "Bitcoin" with the first letter capitalized, which refers to the _Bitcoin System_ and is a proper noun. You will also see "bitcoin", with a lower-case _b_, which refers to the currency unit. Each bitcoin is further subdivided into 100 million units each called a "satoshi" (singular) or "satoshis" (plural)
 ====
 
-=== What is the Lightning Network?
+=== The Lightning Network's defining features
 
 The Lightning Network is a network that operates as a "second layer" protocol on top of Bitcoin and other blockchains. The Lightning Network enables fast, secure, private, trustless, and permissionless payments. Here are some of the features of the Lightning Network:
 
@@ -94,32 +195,12 @@ The Lightning Network is a network that operates as a "second layer" protocol on
  * Unlike transactions on the Bitcoin Network, payments routed on the Lightning Network do not need to be stored permanently. Lightning thus uses fewer resources, hence it is cheaper. This property also has benefits for privacy.
  * The Lightning Network uses onion routing, similar to the protocol used by The Onion Router (Tor) privacy network, so that even the nodes involved in routing a payment are only directly aware of their predecessor and successor in the payment route.
 
-=== Trust in decentralized networks
-
-You will often hear people calling Bitcoin and the Lightning Network "trustless". At first glance this is confusing. After all, isn't trust a good thing? Banks even use it in their names! Isn't a "trustless" system a system devoid of trust a bad thing?
-
-The use of the the word "trustless" is intended to convey the ability to operate without _needing_ trust in the other participants in the system. In a decentralized system like Bitcoin you can always choose to transact with someone you trust. However, the system ensures you can't be cheated even if you can't trust the other party in a transaction. Trust is a nice-to-have instead of a must-have property of the system.
-
-Contrast that to the traditional banking system where you _must_ place your trust in a third party, since they control your money. If they violate that trust you may be able to find recourse in a regulator or court, but you would be facing an enormous power imbalance.
-
-Trustless does not mean devoid of trust. It means that trust is not a necessary prerequisite to all transactions and that you can transact even with people you don't trust because the system prevents cheating.
-
 [[user-stories]]
 === Lightning Network Use Cases, Users, and Their Stories
 
-Any system of money must exhibit, to some degree, the three fundamental properties:
+In order to better understand how the Lightning Network actually works, and why people use it, we'll be following a number of users and their stories.
 
-* Store of Value (SoV) - money must be useful as a store of value over time.
-* Medium of Exchange (MoE) - money can be exchanged for goods and services
-* Unit of Account (UoA) - money is used as a metric unit for measuring the value of things.
-
-Bitcoin is an electronic cash system that exhibits these properties to varying degrees. It has proven to be useful as a store of value and is used as a medium of exchange. Within the cryptocurrency economy, it is sometimes used as a unit of account to measure the exchange rate of other crypto-currencies.
-
-Other relevant properties of digital payment systems include the ability of third parties to use them as a method of control and/or a tool of surveillance.
-
-The invention of money (and in particular Bitcoin) was primarily made to facilitate trade and enable the exchange of value between people. However, without the Lightning Network (or another second layer or scaling solution), it would be infeasible for millions of people to concurrently use Bitcoin as a medium of exchange because the network itself would become overloaded, slow, and costly.
-
-To date, Bitcoin is the longest running, most secure cryptocurrency or electronic cash system and many people believe it represents the most stable store of value of all of the current cryptocurrencies. The Lightning Network allows people to send and receive bitcoin, without the overhead associated with on-chain transactions. This might seem confusing at first. You might be wondering how can the Lightning Network actually achieve this? While we could explain the network in computer science terms, it will be much easier to understand if we examine it from the perspective of people using it. In our examples, some of the people have already used Bitcoin and others are completely new to the Bitcoin network. Each of the people and their stories, as listed here, illustrates one or more specific use cases. We'll be revisiting them throughout this book:
+In our examples, some of the people have already used Bitcoin and others are completely new to the Bitcoin network. Each of the people and their stories, as listed here, illustrates one or more specific use cases. We'll be revisiting them throughout this book:
 
 consumer::
 Alice is a Bitcoin user who wants to make fast, secure, cheap, and private payments for small retail purchases. She buys coffee with bitcoin, using the Lightning Network.
@@ -127,25 +208,18 @@ Alice is a Bitcoin user who wants to make fast, secure, cheap, and private payme
 merchant::
 Bob owns a coffee shop, "Bob's Cafe". "On-chain" Bitcoin payments don't scale for small amounts like a cup of coffee, so he uses the Lightning Network to accept Bitcoin payments almost instantaneously and for low fees.
 
-web designer::
-Saanvi is a web designer and developer in Bangalore, India. She accepts bitcoin for her work, but would prefer to get paid more frequently and so uses the Lightning Network to get paid incrementally for each small milestone she completes. With the Lightning Network, she can do more small jobs for more clients without worrying about fees or delays.
-
-content creator / curator::
-John is a nine-year-old boy from New Zealand, who wanted a games console just like his friends. However, his dad told him that in order to buy it, he had to earn the money himself. Now John is an aspiring artist, so he knows that while he is still improving, he can't charge much for his artwork.
-After learning about Bitcoin, he managed to set up a website to sell his drawings across the internet.
-By using the Lightning Network, John was able to charge as little as $1 for one of his drawings, which would normally be considered a micro-payment and, as such, would typically be impossible on traditional systems.
-Furthermore, most legacy financial systems wouldn't even allow a nine-year old like John to open an account!
-By using a global currency such as bitcoin, John was able to sell his artwork to customers all over the world, store the money he's earned without a bank account and, in the end, buy the games console he so desperately wanted.
+software service business::
+Chan is a Chinese entrepreneur who sells information services related to the Lightning Network, as well as Bitcoin and other cryptocurrencies. Chan is selling these information services over the Internet by implementing micro-payments over the Lightning Network. Additionally, Chan has implemented a liquidity provider service that rents inbound channel capacity on the Lightning Network, charging a small bitcoin fee for each rental period.
 
 gamer::
 Dina is a teenage gamer from Russia. She plays many different computer games, but her favorite ones are those that have an "in-game economy" based on real money. As she plays games, she also earns money by acquiring and selling virtual in-game items. The Lightning Network allows her to transact in small amounts for in-game items as well as earn small amounts for completing quests.
 
-migrant::
-Farel is an immigrant who works in the Middle East and sends money home to his family in Indonesia. Remittance companies and banks charge high fees, and Farel prefers to send smaller amounts more often. Using the Lightning Network, Farel can send bitcoin as often as he wants, with negligible fees.
-
-software service business::
-Chan is a Chinese entrepreneur who sells information services related to the Lightning Network, as well as Bitcoin and other cryptocurrencies. Chan is selling these information services over the Internet by implementing micro-payments over the Lightning Network. Additionally, Chan has implemented a liquidity provider service that rents inbound channel capacity on the Lightning Network, charging a small bitcoin fee for each rental period.
-
 === Chapter Summary
 
-In this chapter, we looked at the history of the Lightning Network and the motivations behind second layer scaling solutions for Bitcoin and other blockchain based networks. We learned basic terminology including node, payment channel, on-chain transactions, and off-chain payments. Finally, we met Alice, Bob, Saanvi, John, Dina, Farel, and Chan who we'll be following throughout the rest of the book. In the next chapter, we'll meet Alice and walk through her thought process as she selects a Lightning wallet and prepares to make her first Lightning payment to buy a cup of coffee from Bob's Cafe.
+In this chapter, we talked about the fundamental concept that underlies both Bitcoin and the Lightning Network: the fairness protocol.
+
+We looked at the history of the Lightning Network and the motivations behind second layer scaling solutions for Bitcoin and other blockchain based networks.
+
+We learned basic terminology including node, payment channel, on-chain transactions, and off-chain payments.
+
+Finally, we met Alice, Bob, Chan and Dina who we'll be following throughout the rest of the book. In the next chapter, we'll meet Alice and walk through her thought process as she selects a Lightning wallet and prepares to make her first Lightning payment to buy a cup of coffee from Bob's Cafe.

contrib/fairness.asciidoc

@@ -53,7 +53,7 @@ Cryptographic systems offer a number of security primitives that can be combined
 - Digital signatures for authentication, non-repudiation, and proof of ownership of a secret.
 - Encryption/decryption to restrict access to information to authorized participants only.
 
-This is only a small list of a whole "zoo" of security and cryptographic primitives that are in use. More basic primitives and combinations are invented all the time.
+This is only a small list of a whole "menagerie" of security and cryptographic primitives that are in use. More basic primitives and combinations are invented all the time.
 
 In our real-life example, we saw one form of fairness protocol called "split and choose". This is just one of a myriad different fairness protocols that can be built by combining the building blocks of security primitives in different ways. But the basic pattern is always the same: two or more participants interact without trusting each other, by engaging in a series of steps that are part of an agreed protocol. The protocol's steps arrange incentives and disincentives to ensure that if the participants are rational, cheating is counter-productive and fairness is the automatic outcome. Enforcement is not necessary to get fair outcomes - it is only necessary to keep the participants from breaking out of the agreed protocol.
 
@@ -71,4 +71,4 @@ The "fairness protocol" pattern can also be found in many different aspects of t
 
 * Those who forward payments know that if they commit funds forward, they can either get a refund or they get paid by the node preceding them.
 
-Again and again, we see this pattern. Fair outcomes are not enforce by any authority. They emerge as the natural consequence of a protocol that rewards fairness and punishes cheating. A fairness protocol that harnesses self-interest by directing it towards fair outcomes.
+Again and again, we see this pattern. Fair outcomes are not enforced by any authority. They emerge as the natural consequence of a protocol that rewards fairness and punishes cheating. A fairness protocol that harnesses self-interest by directing it towards fair outcomes.