sen-material: comparison handouts/ho07.tex

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 The problem with such messages in a distributed system is that
 what happens if Bob receives 10, say, of these transactions?
 Did Alice intend to send him 10 Bitcoins, or did the message
 get duplicated by for example an attacker re-playing a sniffed
 message? What is needed is a kind of serial number for such
-transactions. This means transaction messages shoul look more like
+transactions. This means transaction messages should look more like
 \begin{center}
 $\{\text{I, Alice, am giving Bob Bitcoin \#1234567.}\}_{K^{priv}_{Alice}}$
 \end{center}
 In Bitcoins you have the ability to both combine incoming
 transactions, but also to split outgoing transactions to
 potentially more than one receiver. The latter is also needed.
 Consider again the rightmost transactions in
-Figure~\ref{txngraph} and suppose Alice is a coffeeshop owner
+Figure~\ref{txngraph} and suppose Alice is a coffee shop owner
 selling coffees for 1 Bitcoin. Charles received a transaction
 from Zack over 5 Bitcoins, say. How does Charles pay for the
 coffee? There is no explicit notion of \emph{change} in the
 Bitcoin system. What Charles has to do instead is to make one
 single transaction with 1 Bitcoin to Alice and with 4 Bitcoins
 \subsubsection*{Bitcoins for Real}
-Let us now turn to the nitty gritty details. As a participant
+Let us now turn to the nitty-gritty details. As a participant
 in the Bitcoin network you need to generate and store a
 public-private key pair. The public key you need to advertise
 in order to receive payments (transactions). The private key
 needs to be securely stored. For this there seem to be three
 possibilities
 the private keys and how much security relies on them (recall
 if somebody gets hold of it, your Bitcoins are quickly lost
 forever) I would opt for the third option for anything except
 for trivial amounts of Bitcoins. As we have seen earlier in
 the course, securing a computer system that it can withstand a
-targeted breakin is still very much an unsolved problem.
+targeted break-in is still very much an unsolved problem.
 An interesting fact with Bitcoin keys is that there is no
 check for duplicate addresses. This means when generating a
 public-private key, you should really start with a carefully
 chosen random number such that there is really no chance to
 One question one often hears is how anonymous is it actually
 to pay with Bitcoins? Paying with paper money used to be a
 quite anonymous act (unlike paying with credit cards, for
 example). But this has changed nowadays: You cannot come to a
-bank anymore with a suitcase full of money and try to open a
+bank any longer with a suitcase full of money and try to open a
 bank account. Strict money laundering and taxation laws mean
 that not even Swiss banks are prepared to take such money and
 open a bank account. That is why Bitcoins are touted as
 filling this niche again of anonymous payments.
 \item The government could compel ``mayor players'' to blacklist
 Bitcoins (for example at Bitcoin exchanges, which are usually
 located somewhere in the vicinity of the government's reach).  This
 would impinge on what is called \emph{fungibility} of Bitcoins and
 make them much less attractive to baddies. Suddenly their
-``hard-earned'' Bitcoin money cannot be spent anymore. The attraction
+``hard-earned'' Bitcoin money cannot be spent any more. The attraction
 of this option is that this blacklisting can be easily done
 ``whole-sale'' and therefore be really be an attractive target for
 governments \& Co.
 \item The government could attempt to coerce the developer
 community of the Bitcoin tools. While this might be a

changeset 565	d58f8e3e78a5
parent 564	3391a4fc3533