Week 11: Classical Cryptography

Garden State Cyber I now moves from representation into historical encryption mechanisms.

Classical ciphers are intentionally weak by modern standards, which makes them useful for seeing how keys, substitutions, rearrangements, and repeated patterns affect confidentiality.

This week

Lesson 1: Caesar Cipher: When a Secret Depends on a Tiny Keyspace

Work with plaintext, ciphertext, keys, alphabet shifts, small keyspaces, and pattern leakage. Compare a real cipher goal with simple encoding.

Lesson 2: Transposition and Vigenere: Same Goal, Different Mechanisms

Compare rearrangement with substitution, use a repeating Vigenere keyword, and identify the different patterns each mechanism leaves behind.

Lesson 3: Cryptotheory Lab: Break the Toy Cipher, Explain the Weakness

Solve teacher-provided Caesar, transposition, Vigenere, and encoding-decoy challenges. Build a cryptanalysis ledger and explain the weakness behind every recovered flag.

What you will produce

• Caesar encrypt/decrypt examples
• keyspace analysis
• Vigenere table
• mechanism comparison
• four-station cryptanalysis ledger
• Cryptotheory CTF reasoning records
• weak-cipher failure report

The key idea is:

Ciphertext that looks confusing is not evidence that the cryptographic design is strong.