The main security feature for Bitcoin transactions is the 254-bit private key that enables transactions. The private key generates a unique mathematical signature each time a transaction takes place, ensuring it cannot be stolen or copied, and the user can use the same private key again. When this key is generated, the user should store it in a safe place as it is the only entry to the wallet, and whoever has it can access all the digital assets. Some enthusiasts prefer to memorise the private key, but in case the user forgets the key, for instance, then the cryptocurrencies linked to that address will be lost forever.