Advanced Placement (AP) Computer Science

Which device is an example of one-time pad encryption?

1. Atomic Code Generator

2. The British Bombe

3. The Enigma Machine

4. RSA Encryption Device

The correct answer is: The Enigma Machine

The example of one-time pad encryption is most accurately associated with a method that employs a random key or pad that is used only once and then discarded. The one-time pad ensures complete secrecy, provided that the key is truly random, as long as the key length matches the message length and the key is never reused. The Enigma Machine, however, does not represent one-time pad encryption; it is a cipher machine used primarily by the Germans during World War II, which utilized rotating disk mechanisms to encrypt messages, relying on regular keys that could be reused and which resulted in vulnerabilities. Devices such as an Atomic Code Generator, the British Bombe, and RSA Encryption all serve different functions in cryptography. The Atomic Code Generator deals with quantum principles for secure key generation, while the British Bombe was designed to decode Enigma-encrypted messages, making it unrelated to creating secure one-time pad encryption. RSA, on the other hand, is a public key cryptographic system that relies on mathematical algorithms for security, rather than the concept of a one-time pad. The one-time pad specifically requires a unique, random key that is not regenerated or reused, which distinguishes it from these other encryption methods.