Cipher Portal
Classical ciphers, encrypt and decrypt. Requests go to the API; text is processed in memory on the server and is not stored or logged.
With a known key, decryption is deterministic and fast. If the key is unknown, you can run statistical cryptanalysis; results are approximate and not guaranteed.
Cryptanalysis Lab
Frequency analysis, index of coincidence, Kasiski examination, n-grams, and cipher identification — all in your browser.
Open Cryptanalysis Lab New — Practice PuzzlesCipher Challenges
Crack Caesar, substitution, Vigenère, and mini-Enigma messages with hints, validation, and local achievements.
Start ChallengesInteractive Enigma Machine Simulator
Explore a museum-style Enigma machine with live rotor stepping, lampboard visualization, plugboard wiring, and electrical signal tracing.
Visual Cryptography Lab
Interactive cipher visualization — changes automatically when you select a different cipher.
About Cipher Portal
Cipher Portal is an educational tool for working with classical ciphers such as Vigenère, Caesar, Rail Fence, and substitution ciphers. It can encrypt text with a known key, decrypt text with a known key, and attempt key recovery for selected ciphers using statistical analysis.
What you can do
- Encrypt plaintext to ciphertext when you supply a cipher and key that match the classical definition used on this site.
- Decrypt ciphertext back to plaintext when the key is known, which is deterministic and typically fast.
- Explore key recovery during decryption when a key is missing: the service scores candidate keys using language statistics so you can compare likely readings and numeric confidence hints.
- Review warnings in the UI when assumptions are weak—for example short messages, uncommon spelling, or parameters that produce many plausible candidates.
Supported classical ciphers
This portal focuses on textbook-style alphabetic ciphers: Vigenère (polyalphabetic), Caesar (shift), Rail Fence (transposition), and monoalphabetic substitution. Each cipher has its own key format explained inline next to the form. Detailed guides live on the classical ciphers hub—including Caesar, Vigenère, substitution, and Rail Fence pages—plus how to decrypt without a key and how to identify a cipher.
Key-based decryption vs key recovery
With a verified key, decryption follows the cipher’s mathematical inverse: the same letters or rails are applied in reverse order, so the output matches what you expect from pen-and-paper practice. Key recovery is different—it searches a space of plausible keys or parameters and ranks results heuristically. Outputs can be partially wrong when the ciphertext is ambiguous, unusually short, or drawn from jargon that mismatches statistical language models.
Privacy and processing model
Requests reach a stateless HTTP API that processes text only in RAM for the lifetime of one response. Inputs are not written to persistent storage by this application for retrieval later. Advertising may still set cookies according to Google’s policies. For the full Privacy Policy and Terms of Service, use the footer links.
Stateless: no input is written to disk, logged, or retained after the response. Processing uses RAM on the server only. Ads may be served by Google. This service does not store or log your input.