The concept of the key length of a cryptographic system is familiar. A 128-bit key is commonly used today in a symmetrical cipher, because it’s considered that a brute force attack – trying out all possible keys – is not feasible. Given that there are two to the power of 128 possible keys–that’s 340,282,366,920,938,463,463,374,607, 431,768,211,456 – this seems quite likely. Indeed, it’s been said that if every person on Earth had a computer capable of checking a billion keys per second, all those machines working together would take billions of years to crack a message encrypted with a 128-bit cipher.
And so we come to the Enigma machine, the electromechanical contrivance used for encrypting and decrypting German military communications during WW2. We’ll look at how the number was derived later,…
