We are able to break many classical ciphers because of their vulnerabilities. In cryptography, we learn that a large key space is necessary for secrecy, but understanding how small key spaces make ciphers vulnerable is equally important for learning cryptographic principles. The Shift Cipher is one of the simplest substitution ciphers and provides an excellent introduction to encryption, decryption, key space, and cryptanalysis. Studying its weaknesses helps us understand why modern cryptographic algorithms employ significantly larger key spaces and more sophisticated encryption techniques.

About the experiment:

In this experiment, we work with the well-known historical encryption scheme called the Shift Cipher (also known as the Caesar Cipher), which has a very small key space. Because it has only 25 effective encryption keys for the English alphabet, it can be broken easily using brute-force attacks. You will encrypt and decrypt messages using the Shift Cipher, analyze its key space, and recover the plaintext and secret key from a given ciphertext using brute-force and frequency analysis techniques. This experiment demonstrates the relationship between key space, cryptanalysis, and the security of classical encryption algorithms.