Reciprocal alphabet substitution and modular arithmetic Affine cipher encoder/decoder.
Execution runs 100% locally inside the browser sandbox using HTML5 Canvas, Web Cryptography Subtle API, and Web Workers. Zero egress.
Zero network latency. Operates completely offline with zero dependencies on third-party backend servers or cloud services.
Built according to official RFC specifications, cryptographic test vectors, and enterprise-grade data transformation standards.
Choose Atbash (A ↔ Z), Affine Encrypt, or Affine Decrypt.
For Affine ciphers, select coprime slope key (a) and shift value (b).
Copy the transformed cipher text or plain text.
The Atbash cipher is a monoalphabetic substitution cipher originally developed for the Hebrew alphabet where the first letter maps to the last (A ↔ Z, B ↔ Y).
Key 'a' must share no common factors with 26 so that a unique modular multiplicative inverse exists for unambiguous decryption.
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