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Classic Ciphers: ROT13, Caesar, Atbash and XOR - SimeonOnSecurity

NOTE: This tool runs entirely in your browser with client-side JavaScript. Text and keys are processed locally and are never transmitted, logged, or stored.

When to Reach for These

  • ROT13 and Atbash are self-inverse. Running the same operation twice returns the original, so one button both encodes and decodes.
  • Caesar with all shifts is the useful version. Rather than guessing the offset, read down the list until a line turns into English.
  • XOR with a single-byte key leaves a fingerprint. A one byte key gives a repeating cycle and only 255 candidates, so it falls quickly once you notice the pattern.
  • None of this is cryptography. These are teaching and CTF tools. Anything protecting real data uses a modern authenticated cipher, not a substitution alphabet.

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