When I use InstaWallet.org, do I get my own Bitcoin address?

InstaWallet is an online Bitcoin wallet service. When I visit it for the first time, it generates a Bitcoin address that I can use to deposit to.

I’m wondering whether that address is only ever used for my account, or whether all the coins that InstaWallet receive end up in a single large wallet.

  • If it’s only ever used for my account, I should be able to use blockexplorer to monitor my balance. That’s the case with MyWallet, since they don’t even have access to the address’ private key.
  • On the other hand, if everything goes into a single wallet, it’s possible that other users’ withdrawals may be paid with funds from my deposit address. That’s what happens at MtGox and other exchanges.

So which is it?

Transaction signature generation

When one sets up a transaction, the input of the transaction needs to have a script with a signature to show that you can spend those coins. Which fields of the previous and current transactions need to be concatenated into a message and signed to generate a proper signature? Can someone provide some examples?