Hi this was explained thousands of times on the forum, and for a hero member like you sounds even more extrange.
Bitcoinvanity.com its the website of the creator of vanitygen
here is the link to the post
https://bitcointalk.org/index.php?topic=25804.0Vanitygen has the option to split key whn youre generating a private key
I have a lot of compute power, and want to make vanity addresses for others. How do I do it?
The difficulty with this is convincing your customer that, once you provide them with a vanity address, you do not have a copy of their private key. Some methods of doing this have been discussed on the forum, and vanitygen currently supports one of them. To generate an address securely, your customer generates a private key, and provides you with the public key part. You use this public key as part of the address search, and when you find a match, you provide them with a partial private key. The customer then adds the partial private key to their private key to get the vanity address. Because the customer never disclosed their part of the private key, only they have access to the complete private key.
There are many ways to get a key pair, but to do address-for-hire, you need the complete public key in hexadecimal format. The bitcoin address is not sufficient. One way to generate one and get this is to use the keyconv utility, keyconv -G, and get the following parts:
look arround, they are not storing private keys. its a paid service. they earn a little revenue with the big address