Tool
Caesar Cipher
Shift plaintext letters by a fixed number of positions.
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Classical Ciphers
Historic substitution methods and hand ciphers.
Tools
Tool
Vigenère Cipher
Polyalphabetic substitution cipher using a repeating key.
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Beaufort Cipher
Use a repeating keyword with the reciprocal Beaufort rule C = K - P mod 26.
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Autokey Cipher
Extend a keyword with plaintext letters for a stronger polyalphabetic stream.
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Polybius Square Cipher
Encode letters as row-and-column coordinates using the classic 5x5 Polybius square.
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Affine Cipher
Encrypt text with E(x) = (ax + b) mod 26 using configurable keys and formatting options.
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Hill Cipher
Encrypt letter blocks with square key matrices and modular arithmetic.
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Playfair Cipher
Encrypt letter pairs with a 5×5 keyword square and digraph rules.
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Keyword Cipher
Build a keyed substitution alphabet from a cleaned keyword.
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Bifid Cipher
Mix Polybius square coordinates in fixed-size blocks to create a fractionating classical cipher.
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ADFGX Cipher
Use a keyed ADFGX square followed by keyed columnar transposition.
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ADFGVX Cipher
Use a keyed ADFGVX square with letters and digits, then apply keyed columnar transposition.
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Caesar Cipher: A Secret in Plain Sight
Why the world's easiest cipher to break is still the perfect place to start learning.
Atbash Cipher: The Alphabet in a Mirror
How one of the oldest substitution ciphers turns A into Z, B into Y, and the alphabet into its own reflection.
Hill Cipher: The Day Classical Cryptography Became Mathematical
How Lester S. Hill's 1929 matrix cipher moved secret writing beyond alphabet tricks and toward the logic of modern cryptography.
Vigenère Cipher: When Classical Cryptography Learned to Change Alphabets
How a repeating keyword lets classical cryptography rotate among several alphabets instead of relying on one fixed substitution.
ADFGX and ADFGVX: Fracturing Letters for Wartime Radio
The World War I field ciphers that split characters into coordinates, scattered those coordinates across the page, and made intercepted radio traffic far harder to analyse at speed.