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For K-12 Students · Classical Ciphers

Classical Ciphers for a substitution cipher

Built for k-12 students learning it in middle or high school. Watch the idea come alive with plain-language steps and everyday examples — perfect for projects and homework. Simulate a substitution cipher live below — adjust the inputs and watch it respond, right in your browser.

Classical CiphersLive

Caesar & Vigenère

plaintext

ATTACK AT DAWN

↓ encrypt

ciphertext

DWWDFN DW GDZQ

Controls

Presets

Plaintext

Shift

The Caesar cipher shifts every letter by a fixed amount — trivially broken by trying all 25 shifts or by letter-frequency analysis. The Vigenère cipher uses a repeating keyword so each letter shifts differently, defeating simple frequency attacks for centuries until the key length could be found. Both are insecure today but perfect for learning how ciphers work.

▶ Run in Python

Data Inspector

CipherCaesar +3

Keyspace26

Letters12

Governing equation

E (x) = (x + 3) mod 26

Reading this result: Every letter shifts by the same 3, so this Caesar cipher's 25-key space is cracked instantly by trying all shifts or by letter-frequency analysis.

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Frequently asked questions

Is this good for k-12 students?: Yes — this version of "Classical Ciphers for a substitution cipher" is framed for k-12 students learning it in middle or high school. Watch the idea come alive with plain-language steps and everyday examples — perfect for projects and homework.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.