The PGPfone protocol had little in common with Zimmermann 's popular PGP email encryption package , except for the use of the name .
PGPfone was a secure voice telephony system developed by Philip Zimmermann in 1995 .
The PGPfone protocol had little in common with Philip Zimmermann 's popular PGP email encryption package , except for the use of the name .
PGPfone was a secure voice telephony system developed by Philip Zimmermann in 1995 .