I found a "12345678" which I quite like, and also the ones in my sig.

Just to get near a 50% probability of generating a "1" plus nine case-insensitive letters would take about the same GPU processing time as mining 6 BTC...

If you put what you want here with the bounty, perhaps several people could add your phrase to their list of vanity addresses they are already searching for and you might get lucky. You have to trust that the person who gives you the vanity address is also relinquishing and completely deleting the matching private key, or they would also have access to any bitcoins sent to that address.

It seems like pywallet doesn't support the encrypted wallet format used in the v0.4 Bitcoin client. At least that's what appears to me to be the case from reading the pywallet-thread. Perhaps it would be a good idea to add this information to the first post of this thread, on importing the private key, that pywallet doesn't support an encrypted wallet.dat, since I imagine most people are using this feature.

Can anyone think of a clever way to distribute this: to let us search for the vanity phrases others want aswell as our own

New difficulty challenge to beat: 3,317,130,297,283 (see my signature!)

It would need to be someone trustworthy, as they would also have access to the private key associated with it, no?

As far as I can tell we can't make this distributed in a safe manner. Whoever finds a particular address will need to have had the public part of the EC key pair, which is only valuable with the matching private key. They are always created together, and so, anyone finding a particular address (and it's corresponding key) will have had the opportunity to save the private.

I'd love to be proven wrong on this though.

^ Me neither. Unless we invent a homomorphic encryption scheme to accompany this distributed vanity address generator. But maybe that'd be just a liiitle too much work for cool Bitcoin addresses .

^ Cool! I'm glad you proved me wrong . I don't know anything about EC cryptography but I'll take your word for it.
It means that we could begin building websites where users can buy vanity addresses securely for Bitcoins.

Hmm, I'm on my phone right now, so I can't really check what your variables meant exactly. I'll however explain it in the terms I usually reason in, maybe that will help.

Bitcoin uses a field with some standard, predefined settings. A point in this field is given by two coordinates. A public key is actually just 0x04, and then the two coordinates. You can generate a random point in this field by taking a random number R (smaller than the field size), and adding the field source point to itself R times. The source point (or zero point or something, I'm not sure) is one of the predefined field settings. The random number R is more commonly known as the private key.

So we have a random int as a private key, and this gives a point in the field as a public key.
Now, Person 1 creates Priv1, and subsequently Pub1, and gives Pub1 to Person 2. Person 2 generates a random Priv2, and adds the source point Priv2 times to Pub1. This creates a new point in the field, which is actually the public key associated with the random number (Priv1+Priv2). So that would make it Pub(1+2).

Now, Person 2 can find the address for Pub12, but he'll never be able to claim any bitcoins on the address, because he'd have to sign his transactions with Priv(1+2), but he doesn't have Priv1.


Anyway, the loop here starts after Person 1 sends Pub1 to Person 2. Person 2 can keep generating a new Priv2 to check for niceness, and only has to report back to Person 1 after he has actually found a nice address.

Now, I haven't found a way to generate addresses for a lot of people at the same time though, since everyone gives you a different public key. But it might be possible. The problems involved sound a bit like multiple key authentication, which is being worked on right now. But yeah, for now at least, having one person generating a vanity address for someone else securely is not impossible.