Classical Encryption Techniques: Substitution and Transposition
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Questions and Answers

What are the two basic building blocks of all encryption techniques?

  • Substitution and transposition (correct)
  • Caesar and transposition
  • Transposition and Caesar
  • Substitution and Caesar
  • In a substitution technique, how are the letters of plaintext replaced?

  • By shifting each letter by 3 places (correct)
  • By using random symbols
  • By repeating the same letter
  • By removing certain letters
  • What was the earliest known substitution cipher known as?

  • Shift cipher
  • Transposition cipher
  • Vigenère cipher
  • Caesar cipher (correct)
  • What is the general formula for the Caesar cipher algorithm?

    <p>(p+k) mod 26</p> Signup and view all the answers

    In the Caesar cipher, how many places is each letter of the alphabet shifted?

    <p>3 places</p> Signup and view all the answers

    What does the decryption algorithm do in a substitution technique like the Caesar cipher?

    <p>Reverses the shift done during encryption</p> Signup and view all the answers

    Study Notes

    Classical Encryption Techniques

    • Two fundamental building blocks of encryption techniques: substitution and transposition

    Substitution Techniques

    • Replace plaintext letters with other letters, numbers, or symbols
    • Substitute plaintext bit patterns with ciphertext bit patterns when viewed as a sequence of bits

    Caesar Cipher (Shift Cipher)

    • Earliest known use of a substitution cipher
    • Simplest substitution cipher
    • Replace each letter of the alphabet with the letter standing 3 places further down the alphabet
    • Alphabet is wrapped around, so the letter following "z" is "a"
    • Example: plaintext "pay more money" → ciphertext "SDB PRUH PRQHB"
    • General formula: C = E(p) = (p+k) mod 26, where k is a value in the range 1 to 25
    • Decryption algorithm: reverse of the encryption process

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    Description

    Explore the basic building blocks of encryption techniques including substitution and transposition. Learn about substitution techniques where plaintext letters are replaced by other letters, numbers, or symbols, such as the Caesar cipher (shift cipher).

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