Can vanity address be sold?

[Eli]

Generating a vanity address is pretty easy - fire up a small tool, define what you're looking for, start working, and wait.

This process is kind repeated thousands of times daily (I'm guessing) and someone somewhere is just ignoring the address generated that would satisfy your search.

Assuming we create a network of a list of "wanted" vanity addresses, and every time someone searching for an address, it will also check the global list, and we can find some way to pay each other for found addresses.

Assuming all of the above - how would I know that the vanity address that you've sold me is "safe"? You created it, you have or at least had the private key with you at some point, you could simply wait and check if the address begins to have some coins in it, and when it has enough coins, you simply use your private key that you  sold to me. Problem, right?

Any way around it?

[CIYAM]

Any way around it?

You can apparently generate a private key that has to be combined with another one in order to work (I think this might be something to do with point multiplication), however, I don't know if that would work in the way you are wanting to (as I think the other involved party needs to have sent you a public key before you then generate the private key).

You can find this method in another thread (from memory etotheipi and/or JoelKatz discussed this) which at least is suitable for one person to generate a vanity address for another safely.

[Lord F(r)og]

for creating "safe" addresses check JoelKatz' remarks:
https://bitcointalk.org/index.php?topic=81865.msg901491#msg901491

but I think matching generated with wanted addresses is a difficult task. (not if you managed to gather them before)

[Tuxavant]

I've recently learned that this is possible... the jist of it is :

The buyer generates a keypair and gives the public key to the seller.
The seller generates a second keypair seeded by the buyer public key.
The seller then sends the offset between the keys to the buyer and the buyer applies the offset to his original private key and it ends up being the new vanity keys.

Graingert on IRC pointed me to a thread here, but I can't recall the link. Something about type 2 deterministic keys.

[Eli]

I've recently learned that this is possible... the jist of it is :

The buyer generates a keypair and gives the public key to the seller.
The seller generates a second keypair seeded by the buyer public key.
The seller then sends the offset between the keys to the buyer and the buyer applies the offset to his original private key and it ends up being the new vanity keys.

Graingert on IRC pointed me to a thread here, but I can't recall the link. Something about type 2 deterministic keys.

Sweet. From what I've read so far it's pretty simple and can be done quite easily.

Thanks

[ThePiachu]

Check out this topic for how it can be done, with a working implementation:
https://bitcointalk.org/index.php?topic=84569