Speech compression and encryption (Secure Phone)

[Hadmut Danisch]

Hi folks,

we want to start a project for a computer science class
at the University of Karlsruhe. We want to write software
to use a workstation/PC with a modem, speaker, and microphone
as a secure Phone with encryption and authentication. Therefore
we need speech compression.

Can anyone give me hints to books, articles, algorithms or software 
for speech compression? Is CELP public available?

Thanks a lot

Hadmut