Secure Mail

After hearing a talk from Ed Gibson I thought all this security spam thing could be solved with public private key system. Just imagine how many mails you get from people you don't know. So the idea is: If you want to communicate with someone you send him a 'Communication Invite' You can attache a little message to this with some explanation. Quite like all the social networking sites do it. Attached to this is a public key that is created for one specific email address. If you accept the invite you do the same, you send him a mail with 'Invite accepted' with your public key. Then you both can sign and/or encrypt your mail messages to another. I don't know why ebay, banks, paypal and all the rest don't have a signing scheme? I can imagine my inbox to be structured something around the lines of
- Secure Inbox
- Communication Requests
- Unsecure mail
With this, I would soon have a list of my friends key's and I would know that they are not spamming me.