Merge branch 'develop' into chapter/Chapter5

ch04.asciidoc

@@ -543,7 +543,7 @@ Vanity addresses are valid bitcoin addresses that contain human-readable message
 
 Once a vanity address matching the desired pattern is found, the private key from which it was derived can be used by the owner to spend bitcoins in exactly the same way as any other address. Vanity addresses are no less or more secure than any other address. They depend on the same Elliptic Curve Cryptography (ECC) and Secure Hash Algorithm (SHA) as any other address. You can no easier find the private key of an address starting with a vanity pattern than you can any other address.
 
-In our first chapter, we introduced Eugenio, a children's charity director operating in the Philippines. Let's say that Eugenio is organizing a bitcoin fundraising drive and wants to use a vanity bitcoin address to publicize the fundraising. Eugenio will create a vanity address that starts with "1Kids", to promote the children's charity fundraiser. Let's see how this vanity address will be created and what it means for the security of Eugenio's charity. 
+In our first chapter, we introduced Eugenia, a children's charity director operating in the Philippines. Let's say that Eugenia is organizing a bitcoin fundraising drive and wants to use a vanity bitcoin address to publicize the fundraising. Eugenia will create a vanity address that starts with "1Kids", to promote the children's charity fundraiser. Let's see how this vanity address will be created and what it means for the security of Eugenia's charity. 
 
 ===== Generating Vanity Addresses
 
@@ -575,15 +575,15 @@ Let's look at the pattern "1Kids" as a number and see how frequently we might fi
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-As you can see, Eugenio won't be creating the vanity address "1KidsCharity" any time soon, even if he had access to several thousand computers. Each additional character increases the difficulty by a factor of 58. Patterns with more than seven characters are usually found by specialized hardware, such as custom-built desktops with multiple Graphical Processing Units (GPUs). These are often re-purposed bitcoin mining "rigs" that are no longer profitable for bitcoin mining but can be used effectively to find vanity addresses. Vanity searches on GPU systems are many orders of magnitude faster than on a general-purpose CPU. 
+As you can see, Eugenia won't be creating the vanity address "1KidsCharity" any time soon, even if she had access to several thousand computers. Each additional character increases the difficulty by a factor of 58. Patterns with more than seven characters are usually found by specialized hardware, such as custom-built desktops with multiple Graphical Processing Units (GPUs). These are often re-purposed bitcoin mining "rigs" that are no longer profitable for bitcoin mining but can be used effectively to find vanity addresses. Vanity searches on GPU systems are many orders of magnitude faster than on a general-purpose CPU. 
 
-Another way to find a vanity address is to outsource the work to a pool of vanity-miners, such as the pool at vanitypool.appspot.com. A pool is a service that allows those with GPU hardware to earn bitcoin searching for vanity addresses for others. For a small payment (0.01 bitcoin or approximately $5 when this was written), Eugenio can outsource the search for a 7-character pattern vanity address and get results in a few hours instead of having to run a CPU search for months. 
+Another way to find a vanity address is to outsource the work to a pool of vanity-miners, such as the pool at vanitypool.appspot.com. A pool is a service that allows those with GPU hardware to earn bitcoin searching for vanity addresses for others. For a small payment (0.01 bitcoin or approximately $5 when this was written), Eugenia can outsource the search for a 7-character pattern vanity address and get results in a few hours instead of having to run a CPU search for months. 
 
 ===== Vanity Address Security
 
 Vanity addresses can be used to enhance _and_ to defeat security measures, they are truly a double-edged sword. Used to improve security, a distinctive address makes it harder for adversaries to substitute their own address and fool your customers into paying them instead of you. Unfortunately, vanity addresses also make it possible for anyone to create an address that _resembles_ any random address, or even another vanity address, thereby fooling your customers. 
 
-He could advertise a randomly generated address (e.g. 1J7mdg5rbQyUHENYdx39WVWK7fsLpEoXZy) to which people can send their donations. Or, Eugenio could generate a vanity address that starts with 1Kids, to make it more distinctive. 
+Eugenia could advertise a randomly generated address (e.g. 1J7mdg5rbQyUHENYdx39WVWK7fsLpEoXZy) to which people can send their donations. Or, she could generate a vanity address that starts with 1Kids, to make it more distinctive. 
 
 In both cases, one of the risks of using a single fixed address (rather than a separate dynamic address per donor) is that a thief might be able to infiltrate your website and replace it with their own address, thereby diverting donations to themselves. If you have advertised your donation address in a number of different places, your users may visually inspect the address before making a payment to ensure it is the same one they saw on your website, on your email, and on your flyer. In the case of a random address like "1J7mdg5rbQyUHENYdx39WVWK7fsLpEoXZy", the average user will inspect the first few characters "1J7mdg" perhaps and be satisfied that the address matches. Using a vanity address generator, someone with the intent to steal by substituting a similar-looking address can quickly generate addresses that match the first few characters:
 
@@ -595,8 +595,8 @@ In both cases, one of the risks of using a single fixed address (rather than a s
 | Vanity (6 character match) | 1J7mdg5WxGENmwyJP9xuGhG5KRzu99BBCX
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-So does a vanity address increase security? If Eugenio generates the vanity address "1Kids33q44erFfpeXrmDSz7zEqG2FesZEN", 
-users are likely to look at the vanity pattern word _and a few characters beyond_, for example noticing the "1Kids33" part of the address. That would force an attacker to generate a vanity address matching at least 6 characters (2 more), expending an effort that is 3,364 times (58 x 58) higher than the effort Eugenio expended for a 4 character vanity. Essentially, the effort Eugenio expends (or pays a vanity pool for) "pushes" the attacker into having to produce a longer pattern vanity. If Eugenio pays a pool to generate an 8 character vanity address, the attacker would be pushed into the realm of 10 characters which is infeasible on a personal computer and expensive even with a custom vanity-mining rig or vanity pool. What is affordable for Eugenio becomes unaffordable for the attacker, especially if the potential reward of fraud is not high enough to cover the cost of the vanity address generation. 
+So does a vanity address increase security? If Eugenia generates the vanity address "1Kids33q44erFfpeXrmDSz7zEqG2FesZEN", 
+users are likely to look at the vanity pattern word _and a few characters beyond_, for example noticing the "1Kids33" part of the address. That would force an attacker to generate a vanity address matching at least 6 characters (2 more), expending an effort that is 3,364 times (58 x 58) higher than the effort Eugenia expended for her 4 character vanity. Essentially, the effort Eugenia expends (or pays a vanity pool for) "pushes" the attacker into having to produce a longer pattern vanity. If Eugenia pays a pool to generate an 8 character vanity address, the attacker would be pushed into the realm of 10 characters which is infeasible on a personal computer and expensive even with a custom vanity-mining rig or vanity pool. What is affordable for Eugenia becomes unaffordable for the attacker, especially if the potential reward of fraud is not high enough to cover the cost of the vanity address generation. 
 
 ==== Paper Wallets