Are I and J treated the same?

Yes, to fit 26 letters into a 5x5 (25 cell) matrix, I and J are traditionally treated as the same letter.

What happens with repeated letters?

When the same letters form a pair, X is inserted between them. For example, "BALLOON" is split as "BA LX LO ON".

Can I use it with Japanese?

The traditional Playfair cipher is for 26 alphabetic characters, but you can use it by converting Japanese to Romaji.

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Playfair Cipher

Encrypt digraphs using a 5x5 key matrix with the Playfair cipher. Visualize the encryption process step by step.

Keyword

Cipher Matrix (5×5)

I/J are merged into the same cell

Enter Text

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How to Use

Step 1

Enter Keyword

Enter a keyword to generate the 5x5 key matrix

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Step 2

Enter Message

Enter the message to encrypt or decrypt

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Step 3

Check Result

View the encryption/decryption result and key matrix layout

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Features

Key Matrix Visualization

Display the 5x5 key matrix in a grid and visualize the encryption process

Step Display

Show the encryption/decryption process step by step for each digraph pair

Educational Explanation

Learn Playfair cipher rules (same row, same column, rectangle) with explanations

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FAQ

The Playfair cipher is a classical cipher using a 5x5 character matrix from a keyword, encrypting in digraph pairs. It is more resistant to frequency analysis than simple substitution ciphers.

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