Bitcoin is awesome. Unfortunately, migrating between Bitcoin clients is not. It's especially annoying when the recommended method of exporting with pywallet, importing into BlockChain.info, exporting as an aes.json and importing into MultiBit is 1) incredibly confusing and 2) doesn't actually work.
So, here is how to export your (encrypted) wallet from bitcoin-qt into MultiBit.
- Open up bitcoin-qt and go to the Receive page.
- Go to Help/Debug window from the menubar.
- Switch to the Console tab and enter walletpassphrase <your passphrase> 600. This will ‘unlock’ your wallet for 10 minutes.
- For each of the keys you want to export, enter dumpprivkey <your 34-character bitcoin address>. Copy the resulting 52-character private key into a text document.
- At this point, you should have a list of 34-character Bitcoin addresses and their corresponding 52-character private keys.
- Now, go to a site like BlockChain.info and look up each of your Bitcoin addresses to find out and copy down the oldest transaction on each.
- You now need to convert your data into the correct format, as shown below. The format is <private key> [space] <date>, where <date> is in the format 2013-11-24T15:04Z. Note that I have moved my dates one day backward, just to be safe.
- Save your data file as filename.key and import it in MultiBit through Tools/Import Private Keys.