14. An apparatus comprising: at least one machine-readable medium storing a plurality of voice-prints corresponding to voice characteristics of respective enrolled users; and at least one processor programmed to perform: providing a first prompt to obtain a text-dependent audio sample from a user at an evaluation stage; providing a second prompt to obtain a text-independent audio sample from the user at the evaluation stage; and making an authentication decision about the user based, at least in part, on results of a comparison between characteristics of the text-dependent audio sample and a voice print of an enrollment audio sample received at an enrollment stage and a comparison between a voice print of the text-dependent audio sample and characteristics of the text-independent audio sample.
14. An apparatus comprising: at least one machine-readable medium storing a plurality of voice-prints corresponding to voice characteristics of respective enrolled users; and at least one processor programmed to perform: providing a first prompt to obtain a text-dependent audio sample from a user at an evaluation stage; providing a second prompt to obtain a text-independent audio sample from the user at the evaluation stage; and making an authentication decision about the user based, at least in part, on results of a comparison between characteristics of the text-dependent audio sample and a voice print of an enrollment audio sample received at an enrollment stage and a comparison between a voice print of the text-dependent audio sample and characteristics of the text-independent audio sample. 19. The apparatus of claim 14 , wherein the enrollment audio received at the enrollment stage comprises speech of one or more phrases, and wherein providing the first prompt comprises prompting the user to repeat at least one of the one or more phrases in the evaluation stage.