[ul]I love the idea behind Bitmessage, encrypted email sent using the Bitmesssage protocol. It would be great if we could build the same thing into the PPCoin client. Here is how it would work:
[li]To send any message would cost a very small PPCoin fee. This would reduce spam.[/li]
[li]Let’s say that I sell a physical item that needs to be shipped to the buyer. The item ended up being sold for 590 PPC.[/li]
[li]The PPCoin blockchain would allow me to add information to any transaction, so I send an invoice to the buyer’s PPCoin address. The invoice is embedded into the transaction. Cost to send: 0.01 PPC.
[/li][li]The buyer responds by sending me back an email with his or her mailing address. Cost: 0.01 PPC.
[/li][li]Since the message with the shipping address came from the buyer’s PPCoin address, I know that it is in fact the correct person that I am shipping the item to.
[/li][/list][li]The receipt, shipping address, invoice, and all other pertinent communications are stored in the blockchain forever in an encrypted format. Only the buyer and the seller have the necessary keys to decrypt the information, so they will always be able to retrieve a full record of the transaction for tax purposes, etc.
I’m not a cryptographer, but I am pretty sure that what I am proposing here is possible. The PPCoin email client built into the PPCoin client would work on standard Public Key Encryption. The buyer would reveal his or her PPCoin address by sending the full 590 PPCoin payment to the PPCoin address posted on the seller’s website. This exposes the seller to the public key associated with the buyer’s PPCoin address. The seller can now use this public key to send encrypted messages to the buyer, which can be decrypted by ONLY the buyer using the buyer’s secret private key.
The seller gets the 590 PPC, and sends an invoice/receipt back to the buyer via the blockchain. The buyer now has the seller’s public key, and can send encrypted messages to the seller. Now, the two can communicate back and forth, as much as necessary.