59 %transactions, |
59 %transactions, |
60 % |
60 % |
61 %\end{frame} |
61 %\end{frame} |
62 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
62 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
63 |
63 |
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64 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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65 \begin{frame}[t] |
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66 \frametitle{Last Week's Survey} |
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67 |
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68 {\bf About Bitcoins:} |
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69 |
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70 \begin{textblock}{2.5}(11.5,10) |
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71 \begin{bubble}[2.5cm] |
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72 \it anonymous? |
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73 \end{bubble} |
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74 \end{textblock} |
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75 |
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76 \begin{textblock}{5}(3.5,4) |
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77 \begin{bubble}[5cm] |
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78 \it cannot be controlled by the government? |
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79 \end{bubble} |
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80 \end{textblock} |
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81 |
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82 \begin{textblock}{4}(2,9) |
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83 \begin{bubble}[4cm] |
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84 \it untracable spending of money? |
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85 \end{bubble} |
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86 \end{textblock} |
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87 |
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88 \begin{textblock}{5.7}(3,13) |
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89 \begin{bubble}[5.7cm] |
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90 \it it takes 0..10 mins to pay with Bitcoins |
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91 \end{bubble} |
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92 \end{textblock} |
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93 |
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94 \begin{textblock}{5.6}(8,7) |
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95 \begin{bubble}[5.6cm] |
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96 \it Should one mine for Bitcoins? |
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97 \end{bubble} |
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98 \end{textblock} |
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99 |
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100 \begin{textblock}{2}(12,12.5) |
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101 \begin{bubble}[2cm] |
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102 \it mined by GPUs |
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103 \end{bubble} |
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104 \end{textblock} |
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105 |
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106 \begin{textblock}{3.6}(10,2.3) |
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107 \begin{bubble}[3.6cm] |
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108 \it can be lost or stolen |
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109 \end{bubble} |
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110 \end{textblock} |
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111 |
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112 \end{frame} |
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113 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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114 |
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115 |
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116 |
64 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
117 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
65 \begin{frame}[t] |
118 \begin{frame}[t] |
66 \frametitle{Bitcoins from 10,000m} |
119 \frametitle{Bitcoins from 10,000m} |
67 |
120 |
68 \begin{itemize} |
121 \begin{itemize} |
69 \item a crypto ``currency'' by Satoshi Nakamoto (likely a pen name) |
122 \item a crypto ``currency'' by Satoshi Nakamoto (likely a pen name) |
70 \item a digital resource designed to be scarce |
123 \item a digital resource designed to be scarce |
71 (max 21 Mio bitcoins---deflationary currency) |
124 (max 21 Mio bitcoins---deflationary currency) |
72 \item mined by solving special puzzles involving hashes |
125 \item mined by solving special puzzles involving hashes |
73 \item transaction history (ledger/blockchain) is P2P distributed (12 GB) |
126 \item transaction history (ledger/blockchain) is P2P distributed (12 GB) |
74 \item two ``mining pools'' produce\\ currently more than 50\% |
127 \item three ``mining pools'' produce\\ currently more than 50\% |
75 of bitcoins |
128 of bitcoins |
76 \item can be stolen and also lost |
129 \item can be stolen and also lost |
77 \item anonymous?\pause |
130 \item anonymous?\pause |
78 \item surely a scam/ponzi scheme! |
131 \item surely a scam/ponzi scheme! |
79 \end{itemize} |
132 \end{itemize} |
138 \end{center}\bigskip |
191 \end{center}\bigskip |
139 |
192 |
140 \begin{itemize} |
193 \begin{itemize} |
141 \item no-one else could have created that message |
194 \item no-one else could have created that message |
142 \item Alice cannot deny the ``intend'' of sending Bob money\pause\bigskip |
195 \item Alice cannot deny the ``intend'' of sending Bob money\pause\bigskip |
143 \item forgery possible only after Alice created the string |
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144 \item Q: What is money?\\ |
196 \item Q: What is money?\\ |
145 A: Well a string like above |
197 A: Well a string like above |
146 (or later messages like that) |
198 (or later messages like that) |
147 \end{itemize} |
199 \end{itemize} |
148 |
200 |
159 \bl{$\{\text{I, Alice, am giving Bob one infocoin.}\}_{K^{priv}_{Alice}}$} |
211 \bl{$\{\text{I, Alice, am giving Bob one infocoin.}\}_{K^{priv}_{Alice}}$} |
160 \end{center} |
212 \end{center} |
161 |
213 |
162 \begin{itemize} |
214 \begin{itemize} |
163 \item Alice could keep sending Bob this message over and over |
215 \item Alice could keep sending Bob this message over and over |
164 again (did she mean to send 10 ICs?)\pause |
216 again (did she mean to send 10 ICs?)\bigskip\pause |
165 \item we need to have a serial number |
217 \item we need to have a serial number |
166 \begin{center} |
218 \begin{center} |
167 \bl{$\{\text{I, Alice, am giving Bob infocoin \#1234567.}\}_{K^{priv}_{Alice}}$} |
219 \bl{$\{\text{I, Alice, am giving Bob infocoin \#1234567.}\}_{K^{priv}_{Alice}}$} |
168 \end{center}\pause\medskip |
220 \end{center}\pause\medskip |
169 |
221 |
176 |
228 |
177 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
229 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
178 \begin{frame}[c] |
230 \begin{frame}[c] |
179 \frametitle{No Banks Please} |
231 \frametitle{No Banks Please} |
180 |
232 |
181 With banks we could implement: |
233 With banks we could implement:\medskip |
182 |
234 |
183 \begin{itemize} |
235 \begin{itemize} |
184 \item Bob asks the bank whether the infocoin with that serial |
236 \item Bob asks the bank whether the infocoin with that serial |
185 number belongs to Alice and |
237 number belongs to Alice and |
186 \item Alice hasn’t already spent this infocoin.\bigskip |
238 \item Alice hasn’t already spent this infocoin.\bigskip |
187 \item If yes, then Bob tells the bank he accepts the infocoin. |
239 \item If yes, then Bob tells the bank he accepts the infocoin. |
188 \item The bank updates the records to show that the infocoin |
240 \item The bank updates the records (ledger) to show that the infocoin |
189 with that serial number is now in Bob’s possession and |
241 with that serial number is now in Bob’s possession and |
190 no longer belongs to Alice. |
242 no longer belongs to Alice. |
191 \end{itemize} |
243 \end{itemize} |
192 |
244 |
193 \end{frame} |
245 \end{frame} |
534 |
587 |
535 \item if you want to receive bitcoins, you publicise |
588 \item if you want to receive bitcoins, you publicise |
536 this address |
589 this address |
537 |
590 |
538 \item there are $2^{160}$ possibilities\\ |
591 \item there are $2^{160}$ possibilities\\ |
539 (no check for duplicates) |
592 (no check for duplicates)\bigskip\pause |
540 \end{itemize} |
593 |
541 |
594 \item transactions contain ``payment scripts'' |
542 \end{frame} |
595 (non-Turing-complete scripting language)\bigskip |
543 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
596 |
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597 \small simplest script: pay-to-public-key |
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598 \end{itemize} |
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599 |
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600 \end{frame} |
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601 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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602 |
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603 |
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604 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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605 \begin{frame}[t] |
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606 \frametitle{Multi-Signature Addresses} |
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607 |
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608 \begin{itemize} |
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609 \item \ldots Bitcoin Improvement Proposal\bigskip\pause |
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610 \item pay-to-public-key (explained so far) |
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611 \item pay-to-script-hash (since 2012)\bigskip\pause |
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612 |
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613 can specify: requires \bl{M} out of \bl{N} signatures\medskip |
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614 |
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615 {\small for example\\ |
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616 1-of-2: me and my wife, or\\ |
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617 2-of-2 in banking/companies} |
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618 |
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619 \end{itemize} |
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620 |
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621 \end{frame} |
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622 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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623 |
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624 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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625 \begin{frame}[t] |
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626 \frametitle{Dispute Mediation} |
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627 |
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628 \begin{itemize} |
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629 \item say, client and (online) merchant do not trust |
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630 each other\bigskip\pause |
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631 |
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632 \item 2-of-3: mutually trusted escrow service |
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633 \begin{enumerate} |
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634 \item client sends money to 2-of-3 transaction |
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635 \item merchant sends out goods |
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636 \item if goods are OK, client sends signed transaction |
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637 to merchant, merchant can sign and receive the money |
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638 (publish in blockchain) |
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639 \item if goods are defective, merchant sends signed transaction |
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640 to client, client can sign and receive the money back |
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641 \item if client and merchant disagree, then they ask escrow |
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642 servive who signs a transaction and sends it to ``winning'' |
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643 party |
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644 \end{enumerate} |
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645 \end{itemize} |
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646 |
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647 \end{frame} |
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648 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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649 |
544 |
650 |
545 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
651 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
546 \begin{frame}[c] |
652 \begin{frame}[c] |
547 \frametitle{A Transaction Msg} |
653 \frametitle{A Transaction Msg} |
548 \small |
654 \small |
670 \only<1>{ |
776 \only<1>{ |
671 ledger is public ``forever''; everybody can inspect |
777 ledger is public ``forever''; everybody can inspect |
672 how money was transferred from which address to |
778 how money was transferred from which address to |
673 which address; maybe not ideal for money laundering} |
779 which address; maybe not ideal for money laundering} |
674 \only<2>{ |
780 \only<2>{ |
675 You should use a new pp-pair for \alert{every} transaction; |
781 You should use a new PKI-pair for \alert{every} transaction; |
676 but few do (merchants). A design flaw(?): combining transactions.} |
782 but few do (merchants). A design flaw(?): combining transactions.} |
677 |
783 |
678 \end{frame} |
784 \end{frame} |
679 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
785 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
680 |
786 |
695 de-anonymize `anonymous' social networks. The block chain is a |
801 de-anonymize `anonymous' social networks. The block chain is a |
696 marvellous target for these techniques.'' |
802 marvellous target for these techniques.'' |
697 |
803 |
698 \end{frame} |
804 \end{frame} |
699 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
805 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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806 |
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807 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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808 \begin{frame}[t] |
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809 \frametitle{Other Cryto-Currencies} |
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810 |
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811 Coloured Coins: |
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812 |
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813 \begin{itemize} |
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814 \item record a 1 bitcoin transfer, say, and give it a |
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815 ``colour'' |
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816 |
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817 \item the transaction stands for a share in ``Foo Inc, UK''. |
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818 |
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819 |
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820 \item only makes sense if the share is much more |
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821 valueable than just 1 Bc. |
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822 \end{itemize} |
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823 |
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824 \end{frame} |
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825 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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826 |
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827 |
700 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
828 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
701 \begin{frame}[t] |
829 \begin{frame}[t] |
702 \frametitle{Bitcoin vs Gov} |
830 \frametitle{Bitcoin vs Gov} |
703 |
831 |
704 Purported absence of potential government interference? |
832 Purported absence of potential government interference? |