Re: [tor-talk] Tor as ecommerce platform

[Greg Norcie <greg@xxxxxxxxxx>]

Compressed sensing techniques?

We should keep in mind the barrier for introducing scientific evidence
in US courts is pretty vast. They still use MD5 hashes on forensic
images, because case law specifically says MD5 is acceptable.

Some crazy new correlation attack might be possible... but using it as
evidence in court would be quite difficult.

--
Greg Norcie (greg@xxxxxxxxxx)
GPG key: 0x1B873635

On 8/11/12 6:59 PM, Gregory Maxwell wrote:
> On Sat, Aug 11, 2012 at 1:54 PM, Mike Perry <mikeperry@xxxxxxxxxxxxxx> wrote:
>> But from the paper, it sounds like the BTC flow to Silk Road itself is
>> quite large and might be measurable or at least can be approximated from
>> the website itself...
> [snip]
> 
> Unless I understood the paper, their measurements appear to be based
> on watching listings go up and down,
> which only provides a upper bound on the public activity.
> 
>> The problem is that even with mixes and batching, bitcoin provides a
>> Global Passive Adversary for free, which can be used to map and measure
>> total BTC flow through the network to various sinks (eigenvectors +
>> eigenflow). Based on the established dogma that still rules the Tor
>> threat model, "BTC cannot win!!!1" for this reason.
> 
> When Bitcoin is correctly used the sources and sinks are one-time-use
> pseudonymous locations and the standard operational practices for
> privateâ much less, "I'm a target for wealthy adversaries"â usage is
> to run bitcoin over tor.  the most obvious vulnerable points are on
> the goods and inexplicable income endsâ like in cash.
> 
> With poor use the activity could be very vulnerable to correlation via
> compressed sensing techniques.  I and the other developers have found
> it to be surprisingly hard to convince Bitcoin users how non-private
> their activity can be, even with pointing them to public tracking
> sites. Regardless, I still expect the high profile trouble making
> users to eventually succumb to fairly boring police work rather than
> fancy technical analysis, as usual.
> 
>> At least, not when
>> you're a substantial and atypical chunk of the BTC flow versus norm.
> 
> This is what I really responded to correct.
> 
> In the last 4 hours the Bitcoin network processed 291,326 BTC in
> transactionsâ about 3.3million USD at the current trading prices. In
> _four hours_.  And this doesn't include the significant amount of
> off-network BTC changing hands inside exchanges and bank like
> services, though it may well be double counting coin that effectively
> moved multiple times. (Which cant be measured, because it's not always
> the same coins moving even if its the same 'value' moving, or the
> opposite).
> 
> As long as at least the parties are trusted to not doublespend against
> their counter parties (bad dealing which can be trivially proven to
> ensure that a cheater's reputation is destroyed) it's perfectly
> possible to perform unbounded amounts of party to party transactions
> totally invisibility to the network too, or to form join transactions
> which concurrently settle multiple parties in a single act, and other
> weirdness which makes even estimating the true activity level
> difficulty.   Bitcoin transactions are just a few hundred bytes, and
> there often is no need to make them public in a hurry.  I can think of
> little else of value which could be made more immune to timing
> analysis, if people cared to do so.
> 
> I already think these estimates of underground black-market volumes
> are exaggerated, but it's impossible to know for sure. But the data
> simply does not suggest that this is a substantial chunk of the
> activity.
> 
> Like Tor, Bitcoin suffers from a fair amount of people eager to play
> up the most controversial uses: Some do so to attack it, some because
> it resonates with their juvenile desire to 'stick it to the man', but
> most importantly: its a lot more exciting to present it by emphasizing
> those things, regardless of how (in-)significant they are or how much
> many of the users and developers wish they'd go away.
> 
> Whatever the reasons, skepticism is healthy all around.
> 
>> Like I said, it will be very interesting to watch. It's almost like some
>> aliens came down from space and double-dog-dared the ballsiest,
>> craziest, most aggro humans on the planet to try to solve timing
>> correlation attacks and then called them all pussies, threw the bitcoin
>> source code at their feet, and then flew off. You know, because they
>> needed that shit to interact with our violent monkey society at a safe
>> enough distance and everybody else on this planet had given up. The bad
>> Sci Fi just writes itself. ;)
> 
> If you had any doubts before:  Welcome to the future.
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