History

• From Greek  kryptós, graphein,logia
   
• Secure communication in  the presence of third parties called adversaries
   
• Modern cryptography is heavily based on mathematical theory and computer science  
   
• Legal issues in the information age: many governments classified cryptography as a weapon

Caesar cipher

• Simplest but most widely known encryption technique
   
• Named after Julius Caesar who used it to protect messages   of military significance
   
• Substitution of the cipher where the plaintext is replaced by another letter in the alphabet

ENIGMA

• Used during World War II
   
• Its decryption allowed the allies to win the war
   
• It started the computer era

Symmetric key cryptography

• Sender and receiver share the same key
   
• DES (Data Encryption Standard) and AES (Advanced Encryption Standard) have been designated as Cryptography standards by the U.S. government
   
• Although it is deprecated it is widely used on ATM, e-mail privacy

Asymmetric cryptography

• Sender and receiver have both a public and a private key
   
• The sender uses the receiver's public key to encrypt data
   
• The receiver decrypts data using its private key
   
• RSA is one of the most used asymmetric algorithm

Examples of cryptography

• Uses MTProto Mobile Protocol
  • Developed by the same team that created Telegram
  • Combination of symmetric and asymmetric encryption
     
• Offers US$300,000 to who discovers a security breach
   
• A vulnerability has theorically been found, but can't be practically applied

Telegram

Examples of cryptography

• Security is an essential part of any transaction that takes place over the internet.
• there are 3 requirements for safe e-payments
  • ​Confidentiality
  • Integrity
  • Availabilty
• HTTPS (HTTP over Secure Socket Layer)
  • Extend HTTP internet protocol with
    public key encryption, authentication
    and digital signature.

E-commerce