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Title: When the cookie meets the blockchain: Privacy risks of web payments via cryptocurrencies
Abstract We show how third-party web trackers can deanonymize users of cryptocurrencies. We present two distinct but complementary attacks. On most shopping websites, third party trackers receive information about user purchases for purposes of advertising and analytics. We show that, if the user pays using a cryptocurrency, trackers typically possess enough information about the purchase to uniquely identify the transaction on the blockchain, link it to the user’s cookie, and further to the user’s real identity. Our second attack shows that if the tracker is able to link two purchases of the same user to the blockchain in this manner, it can identify the user’s cluster of addresses and transactions on the blockchain, even if the user employs blockchain anonymity techniques such as CoinJoin. The attacks are passive and hence can be retroactively applied to past purchases. We discuss several mitigations, but none are perfect.  more » « less
Award ID(s):
1651938
PAR ID:
10085438
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Proceedings on Privacy Enhancing Technologies
Volume:
2018
Issue:
4
ISSN:
2299-0984
Page Range / eLocation ID:
179 to 199
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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