The offline wallet never knows your balance, it only knows how to sign (authorize) transactions.

You can pre-download the blockchain, but it'll just save you a day or so, it's probably not worth the effort.

You can always sweep the private keys.  But you should just figure out what's wrong with bitcoin-qt.

I've diagnosed your problem, you should add a 1 at the beginning of your address in your conf file.

I don't think there's much point to using an encrypted drive to move the transactions back and forth, since you're going to publish them publicly anyway.  And you'll need a printer to print your armory backup key as well.

You have like an 80% chance of getting scammed, so you'd need to charge about 500% interest to come out ahead.

You can delete all your posts in the thread.

All that a virus could do is alter the transaction.  So if you made a transaction to send 0.1 from X to Y, the virus could theoretically change that transaction to send 0.1 from X to Z, where Z is the hacker's address.  Then if you sign that transaction in the offline armory it'll send to Z.  But when you sign with the offline armory it'll ask you to double check that you really want to send to Z.  So as long as you do double check the send-to address when signing you'll see that it's been mysteriously changed and you'll know that you've got problems.  Since the online computer can't sign messages since it doesn't have private keys you're pretty safe.

After you've signed the transaction, say from X to Y, a hacker can't change the destination address because then the signature won't match up.

There are two parts to a bitcoin transaction -- the instructions (send 0.1 btc from X to Y) and the signature, which authenticates that you own the coins in X.

The online computer has armory, your addresses, and bitcoin-qt.  It doesn't have your private keys, so it can't actually authorize any transactions.  But it knows your balance, just as if you had typed your address into blockchain.info.  So you can use it to construct an unsigned transaction.

The offline computer has armory and your addresses + private keys.  It has your private keys so it can sign the transaction that the online version created.

To make a transaction:

1.  On your online computer, you create the unsigned transaction.  This says "send 0.1 btc from X to Y".  Save that transaction to a USB drive

2.  Take that USB drive to your offline computer.  Armory will sign the transaction with your private key and save it back to your USB drive.

3.  Take that USB drive back to your online computer and use armory to broadcast the signed transaction over the network.

You can use the netbook and install the offline version, then you keep the online version with bitcoin-qt running on your regular computer.  The offline computer doesn't need bitcoin-qt

If there aren't any coins at that address then just generate a new one.  You can generate as many as you want, there's no need to try and save them.

How does bitcoind generate a wallet.dat from a passphrase?

Yeah you'd have to brute force it.  How's it encrypted? AES?  It'll say at the top.

Technically you could use armory on an infected system.  As long as you have a clean usb boot for the offline portion, the online portion doesn't store any private keys.  Now, a really sophisticated virus could technically change your transactions so that you sign one that sends him your bitcoins, but that's really slick and as long as you double check before signing you're ok.

So where is the wallet stored?  It can't be in your cache because if you delete your cache you'd delete your wallet

If it's encrypted then you need the passphrase

How do you generate additional addresses?

It's probably a good thing, brain wallets are the worst way to store bitcoins and the app you're downloading is probably a fake anyway.

You just need to decrypt it.  Look at the header info and use that encryption and your passphrase.

But what algorithm do you use to generate the private keys from the passphrase?

You'll probably need a little script to poll for incoming transactions.  You could poll getbalance, listunspent, listsinceblock, listreceivedbyaddress, etc and filter by # of confirmations then match up with some database of already processed transactions.