by e-mail or if you leave the backup sheet in an unreliable place at home. Wallet import format is the most common way to represent private keys in blockchain. What we do is taking standard words and mix them to get the key and the address. The wallet import format is shorter, and includes built-in error checking codes so that typos can be automatically detected and/or corrected (which is impossible in hex format). There are well-turned private key combinations in HEX and decimal (yes it is weird but it can be). Because the Bitcoin community is honest and reliable!
Many paths are open to thieves who want private keys. Because the private key is the "ticket" that allows someone to spend bitcoins, it is important that these are kept secure. Specifically, any 256-bit number from 0x1 to 0xffff ffff ffff ffff ffff ffff ffff fffe baae DCE6 AF48 A03B BFD2 5E8C D036 4140 is a valid private key. This is the same private key in (mainnet) wallet import format: private _ KEY When a WIF private key is imported, it always corresponds to exactly one Bitcoin address. The above example has a mini key, which is: SzavMBLoXU6_sample_ private _ KEY _DO_NOT_import_kDrqtUVmffv Summary Any Bitcoins sent to the address can be spent by anybody who knows the private key implementing it in any of the three formats, regardless of when the bitcoins were. Just as with any other transaction, there is risk of swept transactions to be double-spending.
An example of a utility that allows extraction of private keys from your wallet file for printing purposes is pywallet. Check out more information on importing private keys and wallet.