Encoding & Number Bases
Affine Cipher
Encrypt and decrypt text with the affine cipher E(x) = (a·x + b) mod 26.
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What is Affine?
The affine cipher is a Caesar cipher with a multiplier: E(x) = (a·x + b) mod 26. Key a must be coprime with 26 or the mapping is not reversible — the tool validates this immediately.
How it works
Encryption maps each letter through (a·x + b) mod 26; decryption uses the modular inverse of a. The coprime check and the inverse are computed with the Euclidean algorithm.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
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