Substitution Cipher
Encrypt and decrypt with a custom monoalphabetic substitution — supply your own 26-letter key.
Runs locally in your browser. Your input is not uploaded.
How to Use
- 1
Set your cipher alphabet
26 unique letters — e.g. qwertyuiopasdfghjklzxcvbnm.
- 2
Enter text and mode
Encrypt or decrypt with the same key.
- 3
Copy the result
Case is preserved; punctuation passes through.
Frequently Asked Questions
- You define a scrambled alphabet — each plain letter maps to the letter at the same position in your cipher alphabet. Unlike Caesar's fixed shift, the mapping can be any of 26! arrangements.
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