  In recent years, it has come to attention that governments have been doing
mass surveillance of personal communications without the consent of the
citizens. As a consequence of these revelations, developers have begun
releasing new protocols for end-to-end encrypted conversations, extending and
making popular the old Off-the-Record protocol. Several new implementations of
such end-to-end encrypted messaging protocols have appeared, and commonly used
chat applications have been updated with these implementations as well. In this
survey, we compare the existing implementations, where most of them implement
one of the recent and popular protocols called Signal.
  We conduct a series of experiments on these implementations to identify which
types of security and usability properties each application provides. The
results of the experiments demonstrate that the applications have variations of
usability and security properties, and none of them are infallible. Finally,
the paper gives proposals for improving each application w.r.t. security,
privacy, and usability.
