Entries Tagged "bitcoin"

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Nicholas Weaver on Cryptocurrencies

This is well-worth reading (non-paywalled version). Here’s the opening:

Cryptocurrencies, although a seemingly interesting idea, are simply not fit for purpose. They do not work as currencies, they are grossly inefficient, and they are not meaningfully distributed in terms of trust. Risks involving cryptocurrencies occur in four major areas: technical risks to participants, economic risks to participants, systemic risks to the cryptocurrency ecosystem, and societal risks.

I haven’t written much about cryptocurrencies, but I share Weaver’s skepticism.

EDITED TO ADD (8/2): Paul Krugman on cryptocurrencies.

Posted on July 24, 2018 at 6:29 AMView Comments

Regulating Bitcoin

Ross Anderson has a new paper on cryptocurrency exchanges. From his blog:

Bitcoin Redux explains what’s going wrong in the world of cryptocurrencies. The bitcoin exchanges are developing into a shadow banking system, which do not give their customers actual bitcoin but rather display a “balance” and allow them to transact with others. However if Alice sends Bob a bitcoin, and they’re both customers of the same exchange, it just adjusts their balances rather than doing anything on the blockchain. This is an e-money service, according to European law, but is the law enforced? Not where it matters. We’ve been looking at the details.

The paper.

Posted on June 5, 2018 at 6:32 AMView Comments

Tracing Stolen Bitcoin

Ross Anderson has a really interesting paper on tracing stolen bitcoin. From a blog post:

Previous attempts to track tainted coins had used either the “poison” or the “haircut” method. Suppose I open a new address and pay into it three stolen bitcoin followed by seven freshly-mined ones. Then under poison, the output is ten stolen bitcoin, while under haircut it’s ten bitcoin that are marked 30% stolen. After thousands of blocks, poison tainting will blacklist millions of addresses, while with haircut the taint gets diffused, so neither is very effective at tracking stolen property. Bitcoin due-diligence services supplant haircut taint tracking with AI/ML, but the results are still not satisfactory.

We discovered that, back in 1816, the High Court had to tackle this problem in Clayton’s case, which involved the assets and liabilities of a bank that had gone bust. The court ruled that money must be tracked through accounts on the basis of first-in, first out (FIFO); the first penny into an account goes to satisfy the first withdrawal, and so on.

Ilia Shumailov has written software that applies FIFO tainting to the blockchain and the results are impressive, with a massive improvement in precision. What’s more, FIFO taint tracking is lossless, unlike haircut; so in addition to tracking a stolen coin forward to find where it’s gone, you can start with any UTXO and trace it backwards to see its entire ancestry. It’s not just good law; it’s good computer science too.

Posted on March 28, 2018 at 6:30 AM

"Crypto" Is Being Redefined as Cryptocurrencies

I agree with Lorenzo Franceschi-Bicchierai, “Cryptocurrencies aren’t ‘crypto’“:

Lately on the internet, people in the world of Bitcoin and other digital currencies are starting to use the word “crypto” as a catch-all term for the lightly regulated and burgeoning world of digital currencies in general, or for the word “cryptocurrency” — which probably shouldn’t even be called “currency,” by the way.

[…]

To be clear, I’m not the only one who is mad about this. Bitcoin and other technologies indeed do use cryptography: all cryptocurrency transactions are secured by a “public key” known to all and a “private key” known only to one party­ — this is the basis for a swath of cryptographic approaches (known as public key, or asymmetric cryptography) like PGP. But cryptographers say that’s not really their defining trait.

“Most cryptocurrency barely has anything to do with serious cryptography,” Matthew Green, a renowned computer scientist who studies cryptography, told me via email. “Aside from the trivial use of digital signatures and hash functions, it’s a stupid name.”

It is a stupid name.

Posted on December 4, 2017 at 9:14 AMView Comments

Building Smarter Ransomware

Matthew Green and students speculate on what truly well-designed ransomware system could look like:

Most modern ransomware employs a cryptocurrency like Bitcoin to enable the payments that make the ransom possible. This is perhaps not the strongest argument for systems like Bitcoin — and yet it seems unlikely that Bitcoin is going away anytime soon. If we can’t solve the problem of Bitcoin, maybe it’s possible to use Bitcoin to make “more reliable” ransomware.

[…]

Recall that in the final step of the ransom process, the ransomware operator must deliver a decryption key to the victim. This step is the most fraught for operators, since it requires them to manage keys and respond to queries on the Internet. Wouldn’t it be better for operators if they could eliminate this step altogether?

[…]

At least in theory it might be possible to develop a DAO that’s funded entirely by ransomware payments — and in turn mindlessly contracts real human beings to develop better ransomware, deploy it against human targets, and…rinse repeat. It’s unlikely that such a system would be stable in the long run ­ humans are clever and good at destroying dumb things ­ but it might get a good run.

One of the reasons society hasn’t destroyed itself is that people with intelligence and skills tend to not be criminals for a living. If it ever became a viable career path, we’re doomed.

Posted on March 7, 2017 at 8:15 AMView Comments

IoT Ransomware against Austrian Hotel

Attackers held an Austrian hotel network for ransom, demanding $1,800 in bitcoin to unlock the network. Among other things, the locked network wouldn’t allow any of the guests to open their hotel room doors.

I expect IoT ransomware to become a major area of crime in the next few years. How long before we see this tactic used against cars? Against home thermostats? Within the year is my guess. And as long as the ransom price isn’t too onerous, people will pay.

EDITED TO ADD: There seems to be a lot of confusion about exactly what the ransomware did. Early reports said that hotel guests were locked inside their rooms, which is of course ridiculous. Now some reports are saying that no one was locked out of their rooms.

EDITED TO ADD (2/13): More information.

Posted on January 31, 2017 at 8:49 AMView Comments

Tracking the Owner of Kickass Torrents

Here’s the story of how it was done. First, a fake ad on torrent listings linked the site to a Latvian bank account, an e-mail address, and a Facebook page.

Using basic website-tracking services, Der-Yeghiayan was able to uncover (via a reverse DNS search) the hosts of seven apparent KAT website domains: kickasstorrents.com, kat.cr, kickass.to, kat.ph, kastatic.com, thekat.tv and kickass.cr. This dug up two Chicago IP addresses, which were used as KAT name servers for more than four years. Agents were then able to legally gain a copy of the server’s access logs (explaining why it was federal authorities in Chicago that eventually charged Vaulin with his alleged crimes).

Using similar tools, Homeland Security investigators also performed something called a WHOIS lookup on a domain that redirected people to the main KAT site. A WHOIS search can provide the name, address, email and phone number of a website registrant. In the case of kickasstorrents.biz, that was Artem Vaulin from Kharkiv, Ukraine.

Der-Yeghiayan was able to link the email address found in the WHOIS lookup to an Apple email address that Vaulin purportedly used to operate KAT. It’s this Apple account that appears to tie all of pieces of Vaulin’s alleged involvement together.

On July 31st 2015, records provided by Apple show that the me.com account was used to purchase something on iTunes. The logs show that the same IP address was used on the same day to access the KAT Facebook page. After KAT began accepting Bitcoin donations in 2012, $72,767 was moved into a Coinbase account in Vaulin’s name. That Bitcoin wallet was registered with the same me.com email address.

Another article.

Posted on July 26, 2016 at 6:42 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.