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Nihilist and Checkerboard (Polybius) Ciphers

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Terms you will need

  • nihilist cipherA cipher used by Russian Nihilists in the 1880s to send secret messages by converting letters into numbers using a Polybius square and then adding those numbers to a keyword's numbers to create the ciphertext.
  • checkerboard cipherA type of cipher that uses a grid to convert letters into numbers, often used to compress messages and make them harder to break.
  • polybius squareA grid used to convert letters into pairs of numbers, originally used for signaling and later for cryptography.

How this topic runs

  1. 1Start here
  2. 2How it works
  3. 3At competition depth

The Nihilist cipher is a historical encryption method that evolved from the Polybius square, a tool originally designed for telegraphy and cryptography. Developed by Russian Nihilists in the 1880s, it was used to send secret messages during political resistance. The cipher works by converting plaintext and a keyword into numerical values using a Polybius square, then adding these values to produce ciphertext. This method is similar to the Vigenère cipher but uses numbers instead of letters. Later improvements, such as those used by Soviet spies during World War II, incorporated a straddling checkerboard and non-carrying addition to enhance security. These ciphers were vital for covert communication and remain important in understanding the evolution of cryptographic techniques.

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The Nihilist cipher is a type of encryption that builds on the Polybius square. This square is a grid that turns letters into numbers. Each letter is replaced by its row and column number.

For example, the letter 'A' might become '11' and 'Z' might become '55'. Next, you convert both the message you want to send (plaintext) and a secret keyword into these two-digit numbers. The result is the encrypted message (ciphertext).

Later versions of the Nihilist cipher improved security. Also, instead of regular addition, they used non-carrying addition, where each digit is added separately without carrying over. This made the encrypted message more uniform and harder to analyze.

They are important in the history of cryptography and show how encryption methods evolved over time.

Key Points

  • The nihilist cipher is a manually operated symmetric encryption cipher originally used by Russian Nihilists in the 1880s to organize terrorism against the tsarist regime.

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