Substitution Cipher Solver
Compare full n-gram frequencies and search a declared English model.
Try before you buy.
- Free preview: the labels of the result’s rows with every value masked; the answer, the frequency charts and the exports open with a Pro pass.
- Locked until you unlock it: download and copy.
- Unlock: Pro pass, ₹179 for 30 days or ₹79 for 1 week, a one-time payment that never renews. Unlock: Pro pass, $5.99 for 30 days or $2.99 for 1 week, a one-time payment that never renews.
Ways to unlock shows how to get the full result.
Printing this result is locked in the free preview.
Locked in the free preview. Opens the ways to unlock this result.
Locked in the free preview. Batch runs unlock with a pass.
Locked in the free preview. Query results unlock with a pass.
About the Substitution Cipher Solver
Explore monoalphabetic substitution with complete letter, bigram and trigram frequencies against a declared English literary corpus. Use the one-to-one mapping board, keyword or random encoding alphabets, and an automatic quadgram-scored hill-climbing search. The automatic result is a candidate under the chosen model and search budget, not a guaranteed plaintext or modern encryption.
How to use it
- Paste the ciphertext, or plain text to encode, and choose an operation: frequencies, encode, decode, the mapping board or the automatic search.
- Press Run: the free preview shows the labels of the result’s rows, with every value masked.
- With a Pro pass, see the full answer and copy or download it with the report. Editing the text or an option clears the old result.
Method and primary sources
Fitness is the sum of log10 quadgram probabilities with an explicit unseen-window floor. See the [quadgram method](http://practicalcryptography.com/cryptanalysis/text-characterisation/quadgrams/). No count asset from that source is copied. The full declared model is independently generated from complete Pride and Prejudice, Frankenstein, Alice and Great Expectations book bodies, with original notices and attribution retained.
Limitations
- There is no fixed size limit: a very large input depends on your device’s memory, and the tool says so when one is too large.
- Reference frequencies come from the four declared complete literary texts, not a universal English distribution. Short or non-English cryptograms can remain ambiguous.
Privacy
On this device: nothing is sent
What you paste stays in this page’s memory on your device. Nothing is uploaded, looked up on a server or sent to an AI service.
Frequently asked questions
What do I get without a pass?
Without a pass, Substitution Cipher Solver shows the labels of the result’s rows with every value masked; the answer, the frequency charts and the exports open with a Pro pass. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
Does the tool upload my text?
No. Everything runs in this page on your device; only the tool’s own data files load from this site.
What does the free preview show?
The labels of the result’s rows, with every value masked. A Pro pass shows the full answer and the frequency charts, and opens copy and download.