what stops someone from spoofing your wallet?

[pookguy88]

Total noob question here but what stops someone from spoofing your wallet and accepting payments meant for you and/or taking your balance? I mean everyone posts their wallet id/code all over the place.

[BurtW]

Everyone is posting their public Bitcoin addresses.

You need the private key in order to spend the coins.

Your wallet contains your private keys.  Do not give them to anyone.  However, there is no problem giving everyone and anyone the matching public Bitcoin address.

The Bitcoin system relies on public/private key pairs.  These key pairs are designed as follows:

If you have the private key you can calculate the public key.
If you have the public key you can calculate the Bitcoin address.

However:

If you have the Bitcoin address there is no way to calculate back to the public key.
If you have the public key there is no way to calculate back to the private key.

Make sense?

[pookguy88]

so the public key and the Bitcoin address are two different things? how come the Bitcoin address can't calculate the public key?

let's say I backup my private key and restore to a new wallet, does my Bitcoin address stay the same?

[BurtW]

Note that the amount of Bitcoins at every public Bitcoin address is publicly available.  Take this address for example:

1933phfhK3ZgFQNLGSDXvqCn32k2buXY8a

The amount of Bitcoins at this address is available here:

https://blockchain.info/address/1933phfhK3ZgFQNLGSDXvqCn32k2buXY8a

111,114.60824044 BTC or about $91,523,991.66

Anyone can access that information.

However, only the person that has the corresponding private key can spend or move these coins.

Don't you wish you had the private key for this address

Before you ask:  No, there is no way to guess it.

[BurtW]

so the public key and the Bitcoin address are two different things? how come the Bitcoin address can't calculate the public key?

let's say I backup my private key and restore to a new wallet, does my Bitcoin address stay the same?

Yes, the calculation is:

(private key) -> (some math) -> (public key) -> (some more math) -> (Bitcoin address)

The answers at each step are always the same (it is deterministic math)

But:

(Bitcoin address) -> (pubic key) is not possible
(public key) -> (private key) is not possible

[pookguy88]

so what use is the public key?

[BurtW]

so what use is the public key?

You have to calculate the public key before you can calculate the Bitcoin address so it is a step in the process.  Also, when you actually go to spend the coins you have to provide the public key in the transaction to spend the coins so that everyone in the world can verify that you have the right to spend or move the coins (you are the owner of the coins).

When coins get transferred to a new address all that is available to the world is the Bitcoin address.  However, the first time you move coins from this new address to another address you have to provide the public key so now everyone knows the Bitcoin address and the public key (still can't calculate the private key so not a big deal).

[Gabi]

Private key=used to spend bitcoins. From it you generate the public key

Public key=used to receive coins.

From the public key you CANNOT get the private key.