My Notes from "The Code Book"

Highly recommended!

  • Aim of the cryptography is to hide the meaning of the message → a process called encryption.
  • cipher: Name given to any form of cryptography substitution method (or algorithm) in which each letter is replaced by another letter or symbol.

  • Function(Clear Text, Key) = Cipher Text
  • code: substitution at the level of words or phrases
  • cipher: substitution at the level of letters
  • encipher: scramble message using a cipher
  • encode: scramble a message using a code
  • encrypt: encipher or encode
  • Samuel Morse developed the Morse Code and the Telegraph.
    • Morse Code is not a form of encryption.
    • Morse Code is just an alternative alphabet.
    • Morse Code does not conceal the message.
    • Vigenere Cipher has been used to cipher the message → le chiffre indechiffrable!
  • Charles Babbage broke the Vigenere Cipher → Never published, revealed later from his notes.
  • In 1894 Marconi invented the radio
    • drawback of the radio: Messages reach enemy as well as the intended receivers → encryption is a must!
  • Colossus Computer was the first programmable electronic computer → mother of electronic computers.
  • Computers scramble numbers instead of letters.
    • Encryption still proceeds by the old principles of substitution or transposition. Or both.
  • Although computers transformed the implementation of ciphers, the greatest revolution has been the development of the techniques to overcome the problem of key distribution.