Identifying Key Leakage of Bitcoin Users

We study key leakage in the context of cryptocurrencies. First, we consider the problem of explicit key leakage occurring on open-source intelligence platforms. To do this, we monitor the Pastebin feed from Sep 2017–Mar 2018 to find exposed secret Bitcoin keys, revealing that attackers could have stolen 22.40 BTC worth roughly $178,000 given current exchange rates. Then, we focus on implicit key leakage by exploiting the wrong usage of cryptographic primitives and scan Bitcoin’s blockchain for ECDSA nonce reuse. We systematically outline how an attacker can use duplicate r values to leak nonces and secret keys, which goes beyond the simple case where the same nonce and the same key have been used in conjunction more than once. Our results show that ECDSA nonce reuse has been a recurring problem in the Bitcoin ecosystem and has already been exploited by attackers. In fact, an attacker could have exploited nonce reuse to steal 412.80 BTC worth roughly $3.3 million.