Users are promised interoperability between HushMail accounts and desktop PGP users with a tool which uploads PGP public keys to HushMail servers.
A spokeswoman for Hush Communications described it as "a bridge between the two technologies", made possible by the migration of HushMail from proprietary technology to the OpenPGP standard.
Phil Zimmermann, chairman of the OpenPGP Alliance, who was the first to upload his PGP key, said: "Hush's Web based encrypted email has always been simpler for non technical users than PGP, and now it has made a major advancement in interoperability with the rest of the OpenPGP community."
PGP users can upload their public keys to the Hush Key Server Network (using HushTools), enabling Hush users to encrypt and send messages to PGP users or other users of the OpenPGP standard. Previously HushMail users could only send encrypted email to other HushMail users.
Hush has implemented an automated email verifier and certification mechanism that that checks the validity of keys. A description of how to use the service can be found here.
Interoperability between secure communication systems has always been a major stumbling block. Although the availability of HushTools opens up communication between HushMail users and eight million PGP users worldwide its still unclear when encrypted email can be sent to users of the rival S/MIME standard in the same straightforward way. ®