  Learning useful representations from unstructured data is one of the core
challenges, as well as a driving force, of modern data-driven approaches. Deep
learning has demonstrated the broad advantages of learning and harnessing such
representations. In this paper, we introduce a deep generative model
representation learning approach for password guessing. We show that an
abstract password representation naturally offers compelling and versatile
properties that can be used to open new directions in the extensively studied,
and yet presently active, password guessing field. These properties can
establish novel password generation techniques that are neither feasible nor
practical with the existing probabilistic and non-probabilistic approaches.
Based on these properties, we introduce:(1) A general framework for conditional
password guessing that can generate passwords with arbitrary biases; and (2) an
Expectation Maximization-inspired framework that can dynamically adapt the
estimated password distribution to match the distribution of the attacked
password set.
