Bitcoin Address creation

[nookiegirl]

If I create another Bitcoin address in my wallet, how can I be sure that this address has not been created by someone else?
I mean, creating a new address seems instant, what if someone else also has created the same address at around the same time.
What is going to happen then?

[saddambitcoin]

You could check the address at blockchain.info

It is highly unlikely you will ever have a collision, many threads already here discussing this

see: https://bitcointalk.org/index.php?topic=62.0

[nookiegirl]

A thanks for the thread.

Btw, the address creation feels so fast, like a fraction of a second.
How does the network know that the just created address belongs to my wallet?
Is there somewhere I can see that?

[Buffer Overflow]

A thanks for the thread.

Btw, the address creation feels so fast, like a fraction of a second.
How does the network know that the just created address belongs to my wallet?
Is there somewhere I can see that?

The network doesn't know about it until some coins are sent to it.

[nookiegirl]

And what happens if
a) I send coins to an address that does not exist?
b) I send coins to an address that does not exist, but will be created e.g. 4 months later?

[proff]

All the addresses "exist". You will find it difficult to spend the coins without an associated private key, though.

[DannyHamilton]

And what happens if
a) I send coins to an address that does not exist?
b) I send coins to an address that does not exist, but will be created e.g. 4 months later?

It depends on what you mean by "does not exist".

Bitcoin Addresses have a checksum built into them.  It is nearly impossible to make a typo and end up with an address that a wallet will accept as a valid address.

On the other hand, if you intentionally create an address with the proper formatting and checksum, without knowing the private key for that address.  Then you can safely assume that any bitcoins that are sent to that address will be "stuck" at that address and remain unspendable forever.

[DannyHamilton]

If I create another Bitcoin address in my wallet, how can I be sure that this address has not been created by someone else?

Probability.  The odds of two people who generate random addresses actually generating the same address are not just "astronomically unlikely", it is beyond "astronomical".  For all intents and purposes, you can just assume that it's impossible.

I mean, creating a new address seems instant, what if someone else also has created the same address at around the same time.
What is going to happen then?

It is nearly instant.  Your wallet just chooses a random number for the Private Key, and then quickly does some Elliptic Curve multiplication to generate the Public Key.  A few quick SHA-256 and RIPEMD-160 hashes later and you've got a Bitcoin Address.

Nobody is going to randomly choose the same address.  It just isn't going to happen.

But for the sake of argument...

If it did happen, then you both would receive any bitcoins sent to that address, and you both could spend those bitcoins.  If the other person spent them, they would disappear out of your wallet.

[nookiegirl]

Then you can safely assume that any bitcoins that are sent to that address will be "stuck" at that address and remain unspendable forever.

until someone has by chance generated that address - i guess

[DannyHamilton]

Then you can safely assume that any bitcoins that are sent to that address will be "stuck" at that address and remain unspendable forever.

until someone has by chance generated that address - i guess

As I said:

- snip -
The odds of two people who generate random addresses actually generating the same address are not just "astronomically unlikely", it is beyond "astronomical".  For all intents and purposes, you can just assume that it's impossible.
- snip -

[cp1]

You don't create the address.  You just randomly generate a private key and use the corresponding public key as your address.  Imagine a wall of PO boxes with a huge bucket of keys.  You grab a key and then you get to use the PO box that it unlocks.  There's just so many PO boxes that the chances of any person randomly choosing your key in the bucket is really small.