CS 244 ’19: Re-Evaluating Entropy Levels in RSA Key Generation


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Andrew Guan, William Zeng

Original paper: Nadia Heninger, Zakir Durumeric, Eric Wustrow, and J Alex Halder- man. 2012. Mining your Ps and Qs: Detection of widespread weak keys in network devices. In Presented as part of the 21st {USENIX} Security Symposium ({USENIX} Security 12). 205–220.

Through scanning the entire IPv4 address space for TLS certificates, Heninger et. al were able to find a significant amount of RSA public keys that were produced with insufficient entropy, leading to a significant portion of hosts using the same keys, and a smaller (but still significant) portion of hosts using keys with a shared common factor with at least one other host. The latter case is particularly egregious because it allows for efficient factorization of both keys that share the common factor. In this paper, we perform another scan of the Internet to find what proportion of public RSA keys are still vulnerable as outlined in Heninger et al. As expected, we see a changed Internet landscape from Heninger et. al’s original 2012 publication; we find a much greater number of hosts with an open TLS port, yet a much lower number of hosts with vulnerable RSA keys.

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