How to import private keys
When using Cold storage, Paper wallet or Vanity Bitcoin Address you need to import Private keys. Before Bitcoin 0.6.0, you need to rely on third-party wallet.dat manipulation tool such as pyWallet. Since Bitcoin 0.6.0, you can import Private keys using build-in RPC command importprivkey. Here are some instructions for desktop users (official bitcoin-qt client).
As of August 2012, possibly the easiest way to import a private key is using Blockchain.info. Import can be done through the "Import/Export" screen, and when successful, bitcoins can be immediately sent to a new address outside Blockchain.info without needing to wait for any confirmations. An exchange, MtGox will allow individual private keys to be redeemed. There is an API method to import an entire wallet.dat as well.
This article describes how to import a private key through the RPC API of bitcoind, which is a topic for advanced users.
Start Bitcoin client
Unlike third-party wallet.dat manipulation tool such as pyWallet, you do not have to close Bitcoin client before proceeding. In contrary, you need to start the bitcoind server.
Bitcoin-qt do not start with a bitcoind server by default so it cannot accept RPC commands by default. You can do one of this:
- Close bitcoin-qt and start bitcoind -damon in Terminal Emulator. The version of bitcoind MUST be the same as bitcoin-qt!
- Close bitcoin-qt and restart it with bitcoin-qt -server. This will make bitcoin-qt accept RPC commands. You can use your client from both GUI and CLI now!
Unlock your wallet
If you have an encrypted wallet (which is a good idea), you need to unlock it temporarily in memory before importing or exporting Private keys. The RPC commands for unlocking is walletpassphrase <passphrase> <timeout>. But typing this directly in Terminal Emulator will leave your wallet passphrase directly in bash history. You can do this do prevent that:
read x (input you passphrase) bitcoind walletpassphrase "$x" 120 # Do not set the timeout too long or too short.
By doing so, your passphrase will not be recorded into bash history. But be careful with people standing behind you since the passphrase are on your screen...
Import Private key(s)
The last command unlocked your wallet temporarily in memory for 120 seconds. You need to finish importing keys before timed out. Since Private keys are as important as your passphrase, you may want to use these commands to import them instead of typing / pasting them directly in Terminal Emulator to prevent their being recorded in bash history:
read y (type / paste your Private key) bitcoind importprivkey "$y" "my-new-key" # Label can be omitted
The importing process is now started. Bitcoind will rescan the entire block data to ensure this key has not been used before. This process will take about one minute or two, depending on your CPU performance. DO NOT abort it before finishing!
If no errors occurs, the import is a success. If you run your bitcoind via bitcoin-qt, you can see your new address in the GUI now. If you need to import more keys, just repeat the instructions above. Right now there are no ways to import keys in batch so you have to wait one minute or two for every key imported...
bitcoind walletlock unset x unset y
This will lock your wallet again (so you don't have to wait for timeout) and clear the passphrase and Private key from memory. If you start bitcoind in the first way above, you also need to stop it, or bitcoin-qt cannot start again:
If the keys were imported and no longer needed in the origin wallet there might be the desire to delete the keys. As of the bitcoin.org client v0.6, there is no method yet available to delete the keys. Pywallet may allow this.