Abstract
Anonymity networks and hidden services like those accessible in Tor, also called the "darknet", in combination with cryptocurrencies like bitcoin provide a relatively safe environment for criminal online activities. While this is a challenge for law enforcement, it brings opportunities for researchers to monitor these activities as they are often not really hidden but rather obfuscated and/or anonymized. In this paper we discuss such a monitoring approach for product sales in the darknet. We collect bitcoin addresses and data about product offerings in a number of shops run as hidden services in Tor. We then analyze transactions in the bitcoin blockchain that can be mapped to specific product sales in these shops.