Bitcoin private key
Bitcoin private key is a secret number that allows cryptocurrency to be spent. Every Bitcoin address has a matching private key, which is saved in the wallet file of the person who owns the balance. The private key is mathematically related to the address, and is designed so that the Bitcoin address can be calculated from the private key, but importantly, the same cannot be done in reverse.
Because the Bitcoin private key is the “ticket” that allows someone to spend bitcoins, it is important that these are kept secure. Private keys can be kept on computer files, but they are also short enough that they can be printed on paper. An example of a utility that allows extraction of private keys from your wallet file for printing purposes is pywallet.