I dont get it, how does X.509 give us issues with anonymity piotr_n?
You dont really define what the central authority is and what data that central authority retains due to X.509 being implemented in Bitcoin. At least make your case solid by explaining the problem in details instead of screaming out with a tin foil hat on your head.
I said it, but if you insist, I can elaborate.
In order to acquire a certificate (which you need to sign the payment requests with), you must leave your personal details at a CA.
Your full name, your email, where you live, even your phone number.
Who is going to do this? Basically only corporations. Plus maybe a couple of crazy people..
Now, as a payer, you do not need a certificate, but then how does the payment protocol help you with anything?
Obviously you are not going to use it for sending money to your friends or buying stuff on black markets. You are also not going to use it for p2p bitcoin trading, nor for withdrawing your bitcoins from exchanges.
You may only be using it for sending your bitcoins to corporations (or the few crazy people). But each corporations already had a web page secured by SSL certificate - so why the hell to waste bitcoin development resources on them?
Better security? Give me a break! It does not make it anyhow more secure, to let a client extract a payment address from a binary file, rather than to let me just copy it from a web page, protected by the very same certificate.
Also, when you provide the refund address, this address identifies your wallet - another privacy concern.
And of course the recipient - a "very useful" thing, as someone has just said. The thing is that storing the receipts also keeps track of your past payments, which not everyone may be a fan of.
Not to mention that both; receipts and return addresses are already used in the bitcoin world, yet without the payment protocol.
In other words: they spent couple of years of development to reinvent the wheel.
A wheel which now needs a permission from a central certificate authority in order to work.
How crazy is that?
Moreover, let me remind you that very soon after 0.9.0 was released, there was a critical security issue reported in OpenSSL.
Basically a backdoor that could even cause your private keys to leak out from your wallet, through the "secured" payment protocol channel.
It was fixed - yes, but do you really believe that this is going to be the last critical security issue ever discovered in OpenSSL? Well, if you do, then you must be a very naive person and have no much experience with software development. Everyone who is so stubborn to build secured applications around the messy openssl lib is IMHO insane.
BTW, I remember someone once assured me that the bitcoin client would not connect to any server when doing the payment protocol things. No matter what, it wasn't supposed to connect anywhere!
But then it makes me wonder: how is it possible that a payment protocol was vulnerable to the heartbleed bug, if it wasn't connecting anywhere?
Obviously someone had lied to me - obviously there are some connections, just not quite official.
So why did that someone lie to us?
Well, either because he is incompetent and he has no clue what kind of software he develops, or because he is just a liar.
Either way - a wrong person to develop a software for my needs.