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It's indeed a bit more complex than the article (who's link is now broken, apperently the pdf converter crashed... update: v1 seems to still be available, v1 is from 1 november, v2 seems to have crashed, v2 is from 4 november) seems to make out
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Here, I compiled v2 of the paper from its TeX source. There's some error producing the citations but you can still read the text.
https://dl.dropboxusercontent.com/u/3133557/Bitcoin/btcProc.pdf