  How hard is it guess a password? Massey showed that that the Shannon entropy
of the distribution from which the password is selected is a lower bound on the
expected number of guesses, but one which is not tight in general. In a series
of subsequent papers under ever less restrictive stochastic assumptions, an
asymptotic relationship as password length grows between scaled moments of the
guesswork and specific R\'{e}nyi entropy was identified.
  Here we show that, when appropriately scaled, as the password length grows
the logarithm of the guesswork satisfies a Large Deviation Principle (LDP),
providing direct estimates of the guesswork distribution when passwords are
long. The rate function governing the LDP possess a specific, restrictive form
that encapsulates underlying structure in the nature of guesswork. Returning to
Massey's original observation, a corollary to the LDP shows that expectation of
the logarithm of the guesswork is the specific Shannon entropy of the password
selection process.
