I think it's time to update an old fave...
Your post advocates a
(*) technical ( ) legislative ( ) market-based ( ) vigilante
approach to privacy. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)
(*) Any technical solution is only as strong as its weakest point
(*) Regular internet users don't have time for this stuff
(*) It requires finding people you can trust to do the implementation
( ) It is defenseless against brute force attacks
(*) It will slow down the NSA for two weeks and then we'll be stuck with it
( ) Users of email will not put up with it
( ) Microsoft will not put up with it
( ) The police will not put up with it
( ) Requires too much cooperation from the enemy
( ) Requires immediate total cooperation from everybody at once
( ) Many net users cannot afford to lose business or alienate potential employers
(*) The NSA doesn't care how much data it has to crunch
( ) Anyone could anonymously destroy anyone else's career or business
Specifically, your plan fails to account for
( ) Laws expressly prohibiting it
( ) Backdoors intentionally built into commercial equipment
(*) Backdoors intentionally built into commercial software
(*) Known-plaintext attacks on encrypted data
(*) Asshats
( ) Jurisdictional problems
( ) Unpopularity of weird new technologies
( ) Public reluctance to accept weird new forms of communication
( ) Huge existing software investment in HTTP(S)
( ) Susceptibility of protocols other than HTTPS to attack
( ) Infected wireless access points
( ) Armies of worm-riddled broadband-connected Windows boxes
(*) Eternal arms race involved in all cryptographic approaches
( ) Extreme profitability of spying
( ) Identity theft
( ) Technically illiterate politicians
( ) Extreme stupidity on the part of people who use the internet
( ) Dishonesty on the part of spies themselves
and the following philosophical objections may also apply:
(*) Ideas similar to yours are easy to come up with, yet none have ever been shown practical
(*) Any scheme based on opt-out is unacceptable
( ) Cryptography should not be the subject of legislation
( ) We should be able to talk without being censored
( ) Countermeasures should not involve wire fraud or credit card fraud
( ) Countermeasures should not involve sabotage of public networks
( ) Countermeasures must work if phased in gradually
( ) Sending email should be free
( ) Why should we have to trust you and your servers?
( ) Incompatiblity with open source or open source licenses
( ) Feel-good measures do nothing to solve the problem
( ) I don't want the government reading my email
( ) Killing them that way is not slow and painful enough
Furthermore, this is what I think about you:
( ) Sorry dude, but I don't think it would work.
(*) Privacy is dead. Wake up and smell the decay.
( ) Nice try, assh0le! I'm going to find out where you live and burn your house down!