In respect of opening up my account here I like to share some things learned over the last few days.
Got some Bitcoins in my wallet, how to cold store them on paper?I already made some backups of the wallet.dat the bitcoin-qt (original) client uses to store my wallet. But that didn't feel good knowing that this one file could be brute-forced to open the pass-phrase. So after some research the conclusion was: Just knowing the uncompressed private key of the wallet is the only thing needed to store securely on paper ( given the private key only, one can calculate the public Bitcoin address and the blockchain knows the number of btc on this address and stores it forever ).
What I practically did:
- Extracted the real uncompressed private key so I'am independent of the clients backup format
- Using Bitcoin-qt go the Help menu and Enable the Debug window
- Use the command: walletpassphrase "yourpassword" 600
- Now your locked/encrypted wallet has been opened for private commands
- Use the command:dumpprivkey yourbitcoinaddress
- Now you see something like 91b24bf9f5288532960ac687abb035127b1d28a5
- Offline created QRcodes containing the private key and the Bitcoin address using http://sourceforge.net/projects/qrcodegenerator/files/code/
- Without storing on media directly print two copies of the QRcodes and in plaintext to avoid any QRcode reading problems in the future - who knows
This is bad advice that is a good way to lose Bitcoins. If you are advocating this for:
- backing up your wallet: The balance of your bitcoins may not be in the address you see, and the entire contents of one address may be emptied by just one small transfer.
- paper wallet: The whole point is to generate a can't-be-hacked wallet. You've made one on your computer in the way everyone expects you have, leaving data behind on that machine or a log of your activity if you've been hacked and have a key and screen recording trojan horse.
If you are attempting to make a backup of a wallet, there is a backup wallet option in the menu of Bitcoin-Qt.