Seen on another list:

Saw a paper the other day by some Chinese dudes. Talked about how to sell dox online so that the seller don't know what the buyer's gettin, see?

All the dox are on the net for every Tom Harry Dick to look at. But, the catch is they're RSA encrypted to Mr. Seller, just like normal: symmetric cipher on the doc and wrap the key in RSA. Now, Mr. Buyer wants one, so he pays (however) and here's the trick. Buyer asks Seller to decrypt some random RSA data, which of course is, ta da, a BLINDED version of the RSA data Buyer actually wants! Get it?

You pays your money and you gets your choice of one, count em, (1) RSA decryption. Blind it and Seller can't tell what you're buyin.

Simple idea. Why didn't I think of that? Kick self.