Complex sentence: This led Phil Zimmermann to propose the Web of Trust as the PKI infrastructure for the encryption program Pretty Good Privacy (PGP) to deploy PEM were finally abandoned in response to the need to extend the protocol to support MIME.
Split into simpler sentences: This led Phil Zimmermann to propose the Web of Trust as the PKI infrastructure for the encryption program Pretty Good Privacy (PGP). Efforts to deploy PEM were finally abandoned in response to the need to extend the protocol to support MIME.