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  1. 1. Secret Writing
  2. 2. Types of Secret Writing Secret writing Steganography Cryptography
  3. 3. Overview of Cryptography Terminology <ul><li>Cryptographic/Cipher System - A method of disguising a message so only authorized users may read it. </li></ul><ul><li>Cryptology - The study of cryptography. </li></ul><ul><li>Encryption - The process of converting plaintext into ciphertext. </li></ul><ul><li>Decryption - The process of converting ciphertext back to its original plaintext. </li></ul><ul><li>Cryptographic Algorithm - The computational procedure used to encrypt and decrypt messages. </li></ul><ul><li>Cryptanalysis - The process of finding a weakness in, or actual breaking of, a cryptographic system. </li></ul>
  4. 4. <ul><ul><li>Cryptography is the science of information security. </li></ul></ul><ul><ul><li>The word is derived from the Greek  kryptos , meaning hidden. </li></ul></ul><ul><ul><li>Cryptography includes techniques such as merging words with images, and other ways to hide information in storage or transit. </li></ul></ul>
  5. 5. <ul><ul><li>Confidentiality :- the information cannot be understood by anyone for whom it was unintended. </li></ul></ul><ul><ul><li>Integrity  :-the information cannot be altered in storage or transit between sender and intended receiver without the alteration being detected. </li></ul></ul><ul><ul><li>Authentication  :-the sender and receiver can confirm each others identity and the origin/destination of the information. </li></ul></ul>
  6. 6. Overview of Cryptography & Its Applications <ul><ul><li>People wants and needs privacy and security while communicating. </li></ul></ul><ul><ul><li>In the past, cryptography is heavily used for military applications to keep sensitive information secret from enemies (adversaries). </li></ul></ul><ul><ul><li>Nowadays, with the technologic progress as our dependency on electronic systems has increased we need more sophisticated techniques. </li></ul></ul><ul><ul><li>Cryptography provides most of the methods and techniques for a secure communication </li></ul></ul>
  7. 7. 6 Cryptography components
  8. 8. <ul><ul><li>Encryption – It is a process of changing or converting normal text or data information into gibberish text. </li></ul></ul><ul><ul><li>Decryption – It is a process of changing or converting gibberish text back to correct message or data by using encryption method. </li></ul></ul>
  9. 9. 10 Categories of cryptography
  10. 10. <ul><ul><li>A single common encryption key is used to encode and decode messages. </li></ul></ul><ul><ul><li>Both sender and receiver must know the common key. </li></ul></ul><ul><ul><li>The common key need to be exchanged before hand by some other secure method. </li></ul></ul><ul><ul><li>Symmetric encryption is simple and fast. </li></ul></ul><ul><ul><li>But - key management is impractical with large number of senders and receivers. </li></ul></ul>11
  11. 11. 11 Symmetric-key cryptography
  12. 12. Currently Available Crypto Algorithms (private key) <ul><ul><li>DES (Data Encryption Standard) and derivatives: double DES and triple DES </li></ul></ul><ul><ul><li>IDEA (International Data Encryption Standard) </li></ul></ul><ul><ul><li>Blowfish </li></ul></ul><ul><ul><li>RC5 (Rivest Cipher #5) </li></ul></ul><ul><ul><li>AES (Advance Encryption Standard) </li></ul></ul>
  13. 13. <ul><ul><li>Asymmetric system under, which two different keys are used to encrypt and decrypt the message or received data packet. </li></ul></ul><ul><ul><li>On public key is used to encrypt the data or message and the private key on receiving end is used to decrypt the message or data packet. </li></ul></ul><ul><ul><li>Each user has a Public key and a corresponding Private (secret) key </li></ul></ul>12 Asymmetric-key cryptography
  14. 14. Asymmetric-key cryptography
  15. 15. <ul><ul><li>RSA (Rivest, Shamir, Adleman) </li></ul></ul><ul><ul><li>DH (Diffie-Hellman Key Agreement Algorithm) </li></ul></ul><ul><ul><li>ECDH (Elliptic Curve Diffie-Hellman Key Agreement Algorithm) </li></ul></ul><ul><ul><li>RPK (Raike Public Key) </li></ul></ul>Currently Available Crypto Algorithms (public key)
  16. 16. Keys used in cryptography
  17. 17. <ul><ul><li>public-key cryptography Increased security and convenience. </li></ul></ul><ul><ul><li>public-key cryptography is best suited for an open multi-user environment. </li></ul></ul><ul><ul><li>Symmetric encryption is simple and fast. </li></ul></ul>
  18. 18. Steganography <ul><li>Steganography – covered writing – is an art of hiding information </li></ul><ul><li>Popular contemporary steganographic technologies hide information in images </li></ul>
  19. 19. Hiding information in pictures Image in which to hide Text Image to hide within the other image
  20. 20. Digital Watermarks