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 What is meant by cryptography ?     • Its Greek word     • Crypto means “ Secret”      •   Graphie means “ Writing “ Wh...
 CRYPTOGRAPHY COMPONENT
 Cryptanalysis   basic component of cryptography is a cryptosystem      Cryptanalyst          •   Person working for un...
 Cryptosystem   A cryptosystem is a 5-tuple (Ε , D , M , K , C)       •       M is the collection of plaintexts       • ...
 Cryptosystem          Encryption              • Process of encoding (enciphering / encryption ) a message          Dec...
 CRYPTOGRAPHY          CRYPTOGRAP              HYSYMMETRIC-KEY           ASYMMETRIC-CRYPTOGRAPHY                KEY      ...
 Types of Cryptosystems     Symmetric Key Cryptosystems          • Also called single-key cryptosystems          • M = D...
 Symmetric Cryptosystems   Basic techniques for classical ciphers (Encryption)      Substitution           • One letter...
 Transposition Example :-                      Cipher-Text :-          TRHCEEIETGSSMAIAEASS        T   5     T          ...
 Types of Cryptosystems     Asymmetric cryptosystem         • M = D (Kd , E (Ke , M ) )         • The encryption key and...
 Asymmetric Key Cryptosystem  (Public Key Cryptosystem)       Uses public and private keys            • Public key for e...
 RSA Principle   Developed by Ron Rivets , Adi Shamir, and Leonard    Adleman.    (MIT, 1977)                  C = me m...
 RSA Principle{m, e, p, q;                     {C, e, p, q;C= me mod(pq)}                   m=Cd mod(pq)}   Sender       ...
 What is Steganography?           Its Greek Words:                  • STEGANOS – “Covered”                  • GRAPHIE – ...
 History of Steganography             Chinese silk balls             Invisible ink-jet technology             Microdot...
 A Real Example   During WW2 the following cipher message    was actually sent by a German spy      “Apparently, neutral...
 Modern Steganography      Hiding one message within another       (“container”)         Most containers are rich media...
 Steganography System
 ComparisonCryptography   C = Ek (P)             Plain text    P = Dk (C)                         f       Ciphertext     ...
 Hiding a Message in an Image Original Picture    Embedded picture
CryptographyVsStegnoGraphy
CryptographyVsStegnoGraphy
CryptographyVsStegnoGraphy
CryptographyVsStegnoGraphy
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CryptographyVsStegnoGraphy

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CryptographyVsStegnoGraphy

  1. 1.  What is meant by cryptography ? • Its Greek word • Crypto means “ Secret” • Graphie means “ Writing “ Why Cryptography ? • To convert the plain text to unreadable text What is need of Cryptography ?  To secure the Sensitive Information • Username – Password • Credit Card Number etc..
  2. 2.  CRYPTOGRAPHY COMPONENT
  3. 3.  Cryptanalysis basic component of cryptography is a cryptosystem  Cryptanalyst • Person working for unauthorized interceptor  Cryptographer • Person working for legitimate sender or receiver  Cryptology • encryption and decryption
  4. 4.  Cryptosystem  A cryptosystem is a 5-tuple (Ε , D , M , K , C) • M is the collection of plaintexts • K is the set of keys • C is the set of cipher texts  How it works ? o Ε = Μ × K → C is the set of encipher (encryption) o D = C × K → M is the set of deciphering (decryption) Note • Plaintext M : collection of original messages • Cipher text C : set of messages in encrypted form
  5. 5.  Cryptosystem  Encryption • Process of encoding (enciphering / encryption ) a message  Decryption • Process of decoding (deciphering or decryption) an encrypted message to its original form. Alisa Kishan data, control channel messagesdata secure secure data sender receiver Trudy
  6. 6.  CRYPTOGRAPHY CRYPTOGRAP HYSYMMETRIC-KEY ASYMMETRIC-CRYPTOGRAPHY KEY CRYPTOGRAPHY
  7. 7.  Types of Cryptosystems  Symmetric Key Cryptosystems • Also called single-key cryptosystems • M = D(K, E(K, M)) • The encryption key and decryption key are the same
  8. 8.  Symmetric Cryptosystems  Basic techniques for classical ciphers (Encryption)  Substitution • One letter is exchanged for another  Transposition • The order of the letters is rearranged Classical ciphers  Mono-alphabetic • Letters of the plaintext alphabet are mapped into other unique letters  Poly-alphabetic • Letters of the plaintext alphabet are mapped into letters of the cipher text space depending on their positions in the text  Stream • Key stream is generated and used to encrypt the plaintext (Symmetric Key Algorithms)
  9. 9.  Transposition Example :- Cipher-Text :- TRHCEEIETGSSMAIAEASS T 5 T R H 3 H C E E E 1 I E T G K 4 S S M A E 2 I A E S Y 6 S SRefer (by key): IETGIAESHCEESSMATRSS T H E K E Y 5 3 1 4 2 6 Columnar T H I S I S A S E C R E • IEEIRSHSMESCSTATGSEA T M E S S A G E
  10. 10.  Types of Cryptosystems  Asymmetric cryptosystem • M = D (Kd , E (Ke , M ) ) • The encryption key and decryption key are not the same • Kd ≠ Ke
  11. 11.  Asymmetric Key Cryptosystem (Public Key Cryptosystem)  Uses public and private keys • Public key for encryption • Private key for decryption  Examples • RSA • Trapdoor one-way function • Elliptical curve cryptography
  12. 12.  RSA Principle Developed by Ron Rivets , Adi Shamir, and Leonard Adleman. (MIT, 1977)  C = me mod (pq)• P , q : any two large prime numbers (more than 512 bits) • e: public key • d: private key• Knowing C and e, it is “infeasible” to calculate m without knowing d , p and q• Knowing d, p and q, it is easy to find the original plaintext message m = Cd mod (pq)
  13. 13.  RSA Principle{m, e, p, q; {C, e, p, q;C= me mod(pq)} m=Cd mod(pq)} Sender Receiver Intruder {C, e}
  14. 14.  What is Steganography?  Its Greek Words: • STEGANOS – “Covered” • GRAPHIE – “Writing”  Steganography is about Hiding messages  Digital Applications of Steganography • Can be hidden in digital data - MS Word (doc) - Web pages (html) - Sound files (mp3, wav, cda) - Video files (mpeg, avi) - Digital images (bmp, gif, jpg) Today, steganography is used primarily to protect digital rights • “watermarking” copyright notices • “fingerprinting” a serial ID
  15. 15.  History of Steganography  Chinese silk balls  Invisible ink-jet technology  Microdots  Easter eggs  Hiding a message within a text  Shift some words by one point/pixel - Shifted words (or their first letters) make the sentence  Use different fonts - Letter by letter or word by word
  16. 16.  A Real Example During WW2 the following cipher message was actually sent by a German spy “Apparently, neutral’s protest is thoroughly discounted and ignored. Isman hard hit. Blockade issue affect pretext for embargo on by products, ejecting suets and vegetable oils.”  Hidden Message • “ Pershing sails from NY June 1”
  17. 17.  Modern Steganography  Hiding one message within another (“container”)  Most containers are rich media • Images , audio, video ,mp3 etc.  Copyright notices embedded in digital art • Prove ownership  Digital cameras EXIF tags • Not secretive, but hidden from the eyez • Embed info such as camera type, date, shutter speed , focal length,.. Similarly , possible to embed messages in invisible parts of html pages
  18. 18.  Steganography System
  19. 19.  ComparisonCryptography C = Ek (P) Plain text P = Dk (C) f Ciphertext KeySteganography secret message f Stego message cover image
  20. 20.  Hiding a Message in an Image Original Picture Embedded picture

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