Caesar, Vigenère, Gronsfeld and one-time pad: how they work and how to evaluate their security

What this note covers

1. Caesar cipher: mechanism and a worked example
2. Vigenère: a polyalphabetic upgrade
3. Gronsfeld: Vigenère with digits
4. One-time pad: the only unbreakable cipher, and why it is rarely used
5. Ranking the four ciphers and justifying the order
6. Analysing cipher algorithms the way the exam asks

6 sections · 10 key terms & formulas · 6 common mistakes