Are BC addresses portable ?

[MrKain]

I would like to know if my Bitcoin Address is portable -

for example - If I signup to some online wallet site, which generates
me a bitcoinAddress, how can I move this bitcoinaddress from them
to another provider ? - Is this technically not possible, or is it
that the site just doesn't provide this feature -

If they did ? - would it be a simple matter of them giving me my private
key, and then importing this into my own bitcoind ?

MK

[btcidea]

You could get the private key but why use an address when someone else can spend it?

[MrKain]

Ok good point -

Let's say my friend has a bitcoind server and I have a bitcoind server,
each with our respective userbase..

My friend, no longer wants to be involved in the bitcoin business, and
wants to transfer his userbase to me ..

Assuming he has 1000 users, how would I transfer them to my server ?

[MrKain]

Unfortunately, it's a lot more than I need ( an in Java ) --

if anything I want a more stripped down version of bitcoind - everything
except the key store and user managment

[niko]

Ok good point -

Let's say my friend has a bitcoind server and I have a bitcoind server,
each with our respective userbase..

My friend, no longer wants to be involved in the bitcoin business, and
wants to transfer his userbase to me ..

Assuming he has 1000 users, how would I transfer them to my server ?

Your friend dumps private keys, encrypts and signs the dump with PGP, you decrypt and verify the signature, then import the keys.
Assuming you and your friend are capable of running a service for 1000 users, I am also assuming you don't need to ask here in the forum on how to export and import keys.

[MrKain]

why is that ?

When I say capable. I mean we both have high end dedicated servers..

[elebit]

You are asking slightly different questions. How you go about it depends on exactly what you want to do. I don't think you know what you want to do so answering your questions by the letter would do more harm than good, since it is apparent you want to use this information for something else.

A Bitcoin address is a public address, to which anyone can send funds or view in the public ledger. To create a transaction from a Bitcoin address, you need the corresponding key. A wallet in the standard Bitcoin client is a list of addresses and their corresponding keys (which could be encrypted; plus some stuff which makes usage smooth).

If you run a site with external users, you would probably have some software, a wallet, and an internal ledger where you keep track of which user has how much funds (among other things). This situation is not different from if you handled cash or bank transfers for your clients.

This is almost all theoretical information you need. Now your questions make less sense. If you registered an address at an online wallet provider, where you used their software and wallet, you could theoretically export "your" private keys from the service and import to another software, but you would not want to do that. Even if the provider promises to erase all keys that were used for your funds, they are probably around on some backup somewhere and the provider could spend your funds. As to the other situation where you want to take over your friends online service, transferring the accounts and all related data is not really specific to how bitcoin works.

Whether a server is "high end" or not, is completely unrelated to how you use the software, as you probably understand.

[DannyHamilton]

I'm not sure what you are trying to do.

Are you and your friend each providing an "online wallet service" to users, and your friend has decided he no longer wants to provide an "online wallet service"?  So you are trying to have all of the online wallets that your friend is maintaining for his users moved to the wallet service that you are providing?

Or are you and your friend each providing some sort of service where you receive payment in the form of bitcoin.  You have provided each user with a separate "payment address" so the user can pay you in bitcoin for the service that you are providing.  Your friend no longer wants to accept bitcoin as payment, so you want to transfer all of his bitcoin paying customers over to use your service and have them pay you (using the same bitcoin address they previously used) instead?

I'll assume that you are asking about the second option (You are providing a service and the addresses are used to pay you with bitcoin):

The first thing to be aware of is that you really should be generating a new address for each transaction.  The users should have a single address that they pay repeatedly.  Each time a payment is due, a brand new address should be generated and supplied to the user for that single payment.  If you were already doing this, then you wouldn't have this problem.  The users would already be expecting to pay a new address with each payment.  You would generate the address instead of your friend, and the switchover would be simple.

Since you have chosen not to use this recommended practice, you'll have to decide if you want to improve security and reliability by letting all the customers that switch to your server know that the switch will include a new payment address, or if you want to improve convenience for your customers by porting over the addresses.  To port over the addresses, you'll need to acquire the private keys for each address, and then you'll need to import those private keys into whatever wallet you are using.  Note that some wallets do not provide an easy way to export or import private keys.  I can't tell you how to do it (or even if it can be done) without knowing which wallet service you are using.

Here's a question to consider.  Regardless of how much you trust your "friend", if a few months from now, some bitcoins go missing from addresses that you ported over, how will you determine if those addresses were "hacked" or if your friend took the bitcoins without telling you?  If the addresses were truly hacked, would the false suspicion of the possibility of your friend taking the bitcoins get in the way of your friendship?