This led us to ask, if in the worst case users chose multi-word passphrases
with a distribution identical to English speech, how secure would this be?
Using the large Google n-gram corpus we can answer this question for
phrases of up to 5 words. The results are discouraging: by our metrics,
even 5-word phrases would be highly insecure against offline attacks, with
fewer than 30 bits of work compromising over half of users. The returns
appear to rapidly diminish as more words are required. This has potentially
serious implications for applications like PGP private keys, which are
often encrypted using a passphrase.
-- Joseph Bonneau
Within 48 hours of the system going live, we had gained near-complete control of the election server. We successfully changed every vote
and revealed almost every secret ballot. Election officials did not detect
our intrusion for nearly two business days — and might have remained
unaware for far longer had we not deliberately left a prominent clue.
Wolchok, Eric Wustrow, Dawn Isabel, and J. Alex Halderman
in Attacking the Washington, D.C.
Internet Voting System
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