README.md

---
title: Simple Substitution Cipher Decryptor
emoji: 🕵️
colorFrom: blue
colorTo: green
sdk: gradio
app_file: main.py
pinned: false
---

# Simple Substitution Cipher Decryptor

This is a simple tool to automatically decrypt text that has been encrypted with a simple substitution cipher.

**How it works:**
The backend uses n-gram frequency analysis (specifically quadgrams) to score possible decryptions and find the most likely plaintext.

**How to use:**
1.  Paste your ciphertext into the "Ciphertext" box.
2.  (Optional) If you know any letter mappings (e.g., you know 'a' in the ciphertext is 'T' in the plaintext), you can provide them in the "Known Key Mappings" box. The format is `a=T b=E`.
3.  The decrypted plaintext will appear in the "Plaintext" box.

*Note: The decryption process is heuristic and may not always produce a perfect result, especially for short ciphertexts.*