Old Bitcoin transactions can come back to haunt you
A group of researchers from Qatar University and Hamad Bin
Khalifa University have demonstrated how years-old Bitcoin transactions
can be used to retroactively deanonymize users of Tor hidden services.
It seems that Bitcoin users’ past transactions – and especially if
they used the cryptocurrency for illegal deals on the dark web and
didn’t think to launder their payments – may come back to haunt them.
Researchers’ findings
“We crawled 1.5K hidden service pages and created a dataset of 88
Bitcoin addresses operated by those hidden services, including two
ransomware addresses. We also crawled online social networks for public
Bitcoin addresses, namely, Twitter and the BitcoinTalk forum. Out of 5B
tweets and 1M forum pages, we created two datasets of 4.1K and 41K
Bitcoin addresses, respectively. Each address in these user datasets is
associated with an online identity and its corresponding public profile
information,” the researchers explained.
“By analyzing the transactions in the Blockchain, we were able to
link 125 unique users to 20 Tor hidden services, including sensitive
ones, such as The Pirate Bay and Silk Road.”
?What now
Whether law enforcement and intelligence agencies will bother to
replicate and widen the research remains to be seen, but there is no
doubt that the permanence of the Bitcoin blockchain can be exploited for
similar endeavours.
The researchers noted that the online identities to which they tied
the transactions might and might not point directly to individuals, as
it’s possible that these are fake online identities. Still, well
resourced adversaries can perform online surveillance to track down the
users and uncover their true identities.
They also pointed out that this approach can be used to deanonymize only a small number of users.
But for those users who can be linked, the researchers advised that
the best course of action is to clean their social network footprint,
focusing on removing PII that is publicly shared or deleting their
linked online identities altogether – and hope that the information
hasn’t been cached or preserved by digital archive services like the
Internet Archive.
And, in the future, for similar transactions, it might be best to
switch to using alternative coins that provide additional anonymity for
transactions on the blockchain (e.g., Monero, Zcash).
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