Encryptolog y-1216310707267721-9
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Encryptolog y-1216310707267721-9

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Encryptolog y-1216310707267721-9 Encryptolog y-1216310707267721-9 Presentation Transcript

    • Cryptology and Its Applications
    • Presented By
    • CSC STUDENTS
    [ ]
  • [ ] Introduction
    • The science of cryptology is the science of secure communications, formed from the Greek
    • words kryptós , "hidden", and logos , "word".
    • Useful Terminology
      • CIPHERTEXT
      • CODE
      • CRYPTANALYSIS
      • CRYPTOGRAPHY
      • CRYPTOSYSTEM
      • DECRYPTION
      • ENCRYPTION
  • Cryptography
    • PRODUCT CIPHERS
    [ ] A D F G B X A S U B J E C D T A D F G H F I K L M N O G P Q R V W X V Y Z 0 1 2 3 X 4 5 6 7 8 9 M E R C H A N T T A Y L O R S FG AV GF AX DX DD FV DA DA DD VA FF FX GF AA
  • Cryptography
        • Block Ciphers
        • It is a type of symmetric-key encryption algorithm that changes a fixed length of block text into same length of Cipher text.
        • Encryption works by means of key and Decryption is the reverse of encryption process using the same key.
        • Stream Ciphers
        • The encryption method is based on simple XOR of binary bits. It encrypts one bit at a time.
        • The key sequence is generated on highly complex mathematical algorithms. LFSR based on primitive polynomials and combination of several LFSR using linear and nonlinear logic provides a very high level of complexity.
    [ ]
  • Cryptography
    • Public Key Cryptography
      • RSA Algorithm
        • In this system a user chooses a pair of prime numbers so large that factorizing the product is beyond all computing capabilities.
        • Stages of sending the message by this method.
          • The receiver, M, distributes his public key pair.
          • The sender, F, composes a plain text message, m , and then uses Ms public key to encrypt the message and from cipher text, c . c is the remainder left when m is raised to the power of e and divided by the modulus n .
    [ ]
  • Cryptography
          • c = me mod n (where e and n are Ms public key pair).
          • F sends the ciphertext, c , to M.
          • The receiver, M, decrypts the ciphertext and retrieves the plaintext message, m . m is the remainder obtained when c is raised to the power of d and divided by n .
          • m = cd mod n
          • As you can see, this process requires d , which only M knows. Another person, I, who intercepts the message, can not decrypt it.
          • Example:
            • Let p = 5, q = 11, n = pq = 55
            • The least common multiple of ( p-1 )( q-1 ) is 20 = 22 ´ 5.
    [ ]
  • Cryptography
            • Therefore, in this case, any key, e , not divisible by 2 or 5 will have a matching key, d ( e must be relatively prime to ( p-1 )( q-1 ) for it to be the key).
            • Let e = 7
            • (ed -1) mod (p-1)(q-1) = 0 d = 3
            • Let the plaintext message, m = b = 2
            • The ciphertext, c = me mod n = 27 mod 55 = 18
            • To decrypt this information it is necessary to know d.
            • m’ = cd mod n = 183 mod 55 = 2 The message has been successfully decrypted.
    [ ]
  • Cryptography in the "Real World"
    • Applications of Cryptography
      • military and diplomatic services
      • protecting confidential company information, telephone calls
      • Internet Business
      • lottery tickets
    [ ]
  • Cryptanalysis
    • Unlike cryptography which is a clearly defined science, cryptanalysis is as
    • much an art as it is a science.
    • Types of Cryptanalysis: The type used depends on the type of cipher and how much information the cryptanalyst has .
      • Types Of Cryptanalytic Attacks
        • A brute force attack
        • Dictionary attack
        • Ciphertext only attack
        • Chosen plaintext
        • An adaptive chosen plaintext
    [ ]
  • Cryptanalysis
    • A Triumph of Cryptanalysis – Enigma
      • What Was Enigma?
      • The Enigma machine consisted of a 26 letter keyboard for
      • input. The output was read off 26 lamps which each
      • corresponded to a letter. The encipherment was performed
      • by a device called a "scrambler" that was made of three
      • rotating wheels on a common spindle and a plug board
      • known as a "Steckerboard" that added an additional level of
      • security.
    [ ]
  • Cryptanalysis
      • What Made It Possible?
      • With the level of sophistication of the Enigma machines it
      • should have been unbreakable. However, the Germans had
      • a number of procedural flaws which allowed the British
      • and Polish to break the cipher.
    [ ]
  • CONCLUSION
    • Military cryptography for encryption may still remain mainly symmetric key based for obvious reasons.
    • Public key cryptography would develop more in near future particularly in the context of key exchange and digital signatures.
    • Simultaneously , the challenging area of the cryptanalysis, being the other side of the development exercise will gain the importance in the view of the plethora of applications demanding assured security.
    [ ]
  • [ ] THANK YOU !!!