Encryption

• What is encryption


  The process of turning plaintext into scrambled ciphertext
• What is the purpose of encryption

  to keep data secure during transmission
• What is plaintext


  data that is in human-readable form
• What is ciphertext


  Data that has been encrypted and cannot be understood on its own
• What is a cipher

  A method of transforming a text in order to conceal its meaning

  ie the WAY something is encrypted
• What is the caesar cipher

  A substitution cipher where one character of plaintext is substituted for another, making it ciphertext
• What makes the caesar cipher so weak(2)

  • Limited number of possible shifts, meaning an attacker can use trial and error to decipher the text
  • English uses some letters more frequently than others, making it easier to crack
• What is the vernam cipher

  A method of encryption that uses a one-time pad (key) to create a ciphertext that is mathematically impossible to solve w/o the key
• What is the method for a vernam cipher (4)

  • The key/one-time pad is created, which is a completely random sequence of letters
  • Each plaintext letter is assigned a letter at the corresponding position in the key
  • all the characters are turned into binary, and a logical XOR is performed on the two values
  • The resulting binary values are converted back to find their corresponding letters
• What makes a vernam cipher perfectly secure (2)

  • The key that is used is entirely random, making it impossible to guess
  • Once one key has been used in a cipher, it is destroyed making it impossible to reuse the same key
• What is computational security

  A concept of how secure data encryption is
• Explain the computational security of a vernam cipher and other ciphers (2)

  • Vernam ciphers are the only ciphers that are considered 100% mathematically secure
  • Theoretically, every cipher except Vernam cipher can be broken