🏛️ Caesar & Vigenère

🇺🇦 UK ← Back
Input Message
Mode: Caesar Chars: 0 Letters: 0
Letter Frequency — Input
English reference: E T A O I N S H R D L C U M W F G Y P B
Ciphertext (Encrypted)
Shift: 3 IC: —
Letter Frequency — Output
Frequency shift visible for Caesar cipher

🔐 Caesar & Vigenère Ciphers

Encrypt and decrypt messages using two classical substitution ciphers. Apply frequency analysis to break them — seeing why simple substitution ciphers are vulnerable to statistical attacks.

🔬 What It Demonstrates

The Caesar cipher shifts each letter by a fixed amount; the Vigenère cipher uses a repeating keyword to shift each letter by a different amount. Frequency analysis reveals the key by comparing letter distributions against known language statistics.

🎮 How to Use

Type a message, choose a key, and watch the ciphertext appear. The frequency histogram shows letter distributions. The attack panel tries all possible keys (Caesar) or uses the Index of Coincidence (Vigenère).

💡 Did You Know?

The Vigenère cipher was considered unbreakable for 300 years until Charles Babbage and Friedrich Kasiski independently discovered statistical attacks in the 1860s.