The danger with the PGP system is that it could be easily perverted into a British style trusted-third-party system for GAK. The government would set up a key management infrastructure to provide an official repository and CA to register keys. It could even be "voluntary" if only government-approved CAs had liability protection which private CAs didn't have, making it hard for the privates to compete. However the price to use the government registry is that each key has to use the PGP features to specify a TTP as an additional recipient. Every message encrypted to that key should also be encrypted to the TTP key. Only government-approved TTPs may be used, and although there are many to choose from, all have to provide easy and secret GAK. The PGP 5 software will then automatically encrypt to the TTP key. Yes, this can be defeated using superencryption or faking the additional-recipient block in the message. But we know any scheme can be defeated. It still satisfies the government's requirement to get routine access to most email communications, and to allow criminals who use standard email packages to be watched.