[cryptography] Mining Your Ps and Qs: Detection of Widespread Weak Keys in Network Devices

[Jeffrey Walton]

More results on weak keys (it looks more comprehensive than results
from the EFFbs SSL Observatory). The authors also do a nice job on the
Linux Random Number Generator in Section 5.1.

https://factorable.net/paper.html

Abstract

RSA and DSA can fail catastrophically when used with malfunctioning
random number generators, but the extent to which these problems arise
in practice has never been comprehensively studied at Internet scale.
We perform the largest ever network survey of TLS and SSH servers and
present evidence that vulnerable keys are surprisingly widespread. We
find that 0.75% of TLS certificates share keys due to insufficient
entropy during key generation, and we suspect that another 1.70% come
from the same faulty implementations and may be susceptible to
compromise. Even more alarmingly, we are able to obtain RSA private
keys for 0.50% of TLS hosts and 0.03% of SSH hosts, because their
public keys shared nontrivial common factors due to entropy problems,
and DSA private keys for 1.03% of SSH hosts, because of insufficient
signature randomness. We cluster and investigate the vulnerable hosts,
finding that the vast majority appear to be headless or embedded
devices. In experiments with three software components commonly used
by these devices, we are able to reproduce the vulnerabilities and
identify specific software behaviors that induce them, including a
boot-time entropy hole in the Linux random number generator. Finally,
we suggest defenses and draw lessons for developers, users, and the
security community.
b&
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