MMW (QUIZ 2)

• Cryptography is the science of encrypting and decrypting written communication.
• It comes from the Greek word “kryptos,” meaning hidden and “graphia,” meaning writing. 
• Encryption is the process of . 

  1. Transforming data 
  2. Using an algorithm 
  3. To make it unreadable to anyone 
  4. Except those possessing the key 
• Cryptography is an effective way of protecting sensitive information as it is stored on media or transmitted through network communication paths
• Encryption is the process of

  1. Transforming data 
  2. Using an algorithm 
  3. To make it unreadable to anyone 
  4. Except those possessing the key 
• ENCRYPTION: PLAIN TEXT + KEY ….. ALGORITHM …… CIPHER TEXT 
• DECRYPTION: CIPHER TEXT + KEY….. ALGORITHM….. PLAIN TEXT
• Cipher text is the encrypted or encoded information that contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it. 
• Decryption is the process of taking encoded or encrypted text or other data and converting it back into text that you or the computer can read and understand. 
• A cipher (or cypher) is an algorithm for performing encryption or decryption - a series of  well-defined steps that can be followed as a procedure. 
• The operation of a cipher usually depends  on a piece of auxiliary information, called a key. 
• Cryptanalysis is the science and sometimes art of breaking cryptosystems
• Cryptology: the scientific study of cryptography and cryptanalysis
• Cryptology - Cryptography + Cryptanalysis
• Goals of cryptography 

  1. Privacy 
  2. Authentication 
  3. Data integrity 
• • Cryptography exists in the form of code breaking during World War II such as the famous attack against the German Enigma encryption. 
• The Enigma machines were a series of electro-mechanical rotor cipher machines developed and used in the early - to mid- 20th century to protect commercial, diplomatic and military communication.
• • Cryptography was also used  as early as the time of ancient Greece through their secret writing called Scytale of Sparta 
• • Around 400 C, the Spartans would write a message on a strip of paper that is wound around a wooden stick or rod, the Scytale 
• The strip was delivered and then the recipient will wrap it around a different rod. The message is only readable when the rod is the same size as the original rod.
• Substitution Ciphers is a method of encryption by which units of plain text are replaced by cipher text according to regular systems. 
• Monoalphabetic Cipher is a type of Substitution Cipher that replaces each letter in the message with a different letter. 
• The most famous method of this type are: 

  1. Caesar Cipher 
  2. Atbash Cipher 
  3. Affine Cipher 
  4. ROT13 Cipher
• Julius Caesar allegedly used a cyclical alphabet encrypting code to communicate with his generals. 
• Caesar cipher: In this approach, each letter is replaced with a letter some fixed number of positions later in the alphabet.
• Transposition Ciphers  is one in which the order of characters is changed to obscure the message.
• An early version of the transposition cipher was a Scytale. 
• This is a form of a transposition cipher, whereby the letters of the plaintext are shuffled without being changed to different letters or symbols. 
• Transposition Cipher Types 

  1. Rail Fence Cipher 
  2. Route Cipher 
  3. Simple Columnar Cipher 
  4. Keyword Columnar Cipher
• Simple Columnar Ciphers : This cipher technique simply arranges the plain text as a sequence of rows of a rectangle that are read in columns.
• Keyword columnar Cipher : A more complex version of the simple columnar cipher can be created by specifying an order in which the columns should be recorded.
• To make the encryption key easier to remember, a word can be used (KEYWORD).