In a brute force attack, all digits, letters and special characters are tried up to a maximum word length. Brute force attacks can be used on encrypted passwords, files, messages and information. To make brute force attacks as time-consuming as possible, most encryption systems use very long keys. For a 32-bit key, it would be four billion possibilities that today's personal computers would have tried through in minutes. It takes a correspondingly longer time to determine a 48-bit key or even a 64- or a 128-bit key, which would take several thousand years to crack.