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Vigenere Cipher and Frequency Analysis

Encrypt with a keyword and break the cipher by splitting the message and using frequency analysis on each part.

Grade 10Math ChallengeScience OlympiadMathTechnologyLogicCodingNumber SenseAdvanced1 to 1.7 hr4 materials

What you'll learn

  • Encrypt and decrypt with a repeating keyword
  • Estimate key length using repeated patterns or the index of coincidence
  • Break each column as a Caesar cipher

Objective

Implement the Vigenere cipher, find the key length of a coded message, and break the cipher using frequency analysis.

STEM concepts

Polyalphabetic ciphersKasiski examinationFrequency analysisAlgorithms
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Step-by-step instructions
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Why does it work, challenge and project report

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