actually ... it looks like this program has fallen out of development.
according to MIT
Phil's Pretty Good Software Presents...
PGPfone - Pretty Good Privacy Phone
MIT is no longer distributing PGPfone. Given that the software has not been maintained since 1997, we doubt it would run on most modern systems.
and according to pgpi -
http://www.pgpi.org/products/pgpfone/What is it?
PGPfone (Pretty Good Privacy Phone) is a software package that turns your desktop or notebook computer into a secure telephone. It uses speech compression and strong cryptography protocols to give you the ability to have a real-time secure telephone conversation. Secure voice calls are supported over the Internet, or through a direct modem-to-modem connection, or even over AppleTalk networks.
PGPfone 1.0 is freeware. It is available for both Macintosh (1.0b7) and Windows 95/NT (1.0b2).
PGPfone 2.x is a commercial product, but NAI has shown no interest in it, so it is probably O.K. to use it anyway. If you want to contribute to PGPfone development, please look here.
Do you currently use this program akis?