  In this paper, we present AltVoice -- a system designed to help user's
protect their privacy when using remotely accessed voice services. The system
allows a user to conceal their true voice identity information with no
cooperation from the remote voice service: AltVoice re-synthesizes user's
spoken audio to sound as if it has been spoken by a different, private
identity. The system converts audio to its textual representation at its
midpoint, and thus removes any linkage between the user's voice and the
generated private voices. We implement AltVoice and we propose six different
methods to generate private voice identities, each is based on a user-known
secret. We identify the system's trade-offs, and we investigate them for each
of the proposed identity generation methods. Specifically, we investigate
generated voices' diversity, word error rate, perceived speech quality and the
success of attackers under privacy compromise and authentication compromise
attack scenarios. Our results show that AltVoice-generated voices are not
easily linked to original users, enabling users to protect themselves from
voice data leakages and allowing for the revocability of (generated) voice
data; akin to using passwords. However the results also show further work is
needed on ensuring that the produced audio is natural, and that identities of
private voices are distinct from one another. We discuss the future steps into
improving AltVoice and the new implications that its existence has for the
creations of remotely accessed voice services.
