Cryptography

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This technology is highly essential
to hide a message that is being transferred in a public Network.

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Cryptography

  1. 1. <ul><li>Cryptology and Its Applications </li></ul><ul><li>Presented By </li></ul><ul><li>IQxplorer </li></ul>[ ]
  2. 2. [ ] Introduction <ul><li>The science of cryptology is the science of secure communications, formed from the Greek </li></ul><ul><li>words kryptós , &quot;hidden&quot;, and logos , &quot;word&quot;. </li></ul><ul><li>Useful Terminology </li></ul><ul><ul><li>CIPHERTEXT </li></ul></ul><ul><ul><li>CODE </li></ul></ul><ul><ul><li>CRYPTANALYSIS </li></ul></ul><ul><ul><li>CRYPTOGRAPHY </li></ul></ul><ul><ul><li>CRYPTOSYSTEM </li></ul></ul><ul><ul><li>DECRYPTION </li></ul></ul><ul><ul><li>ENCRYPTION </li></ul></ul>
  3. 3. Cryptography <ul><li>PRODUCT CIPHERS </li></ul>[ ] 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
  4. 4. Cryptography <ul><ul><ul><li>Block Ciphers </li></ul></ul></ul><ul><ul><ul><li>It is a type of symmetric-key encryption algorithm that changes a fixed length of block text into same length of Cipher text. </li></ul></ul></ul><ul><ul><ul><li>Encryption works by means of key and Decryption is the reverse of encryption process using the same key. </li></ul></ul></ul><ul><ul><ul><li>Stream Ciphers </li></ul></ul></ul><ul><ul><ul><li>The encryption method is based on simple XOR of binary bits. It encrypts one bit at a time. </li></ul></ul></ul><ul><ul><ul><li>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. </li></ul></ul></ul>[ ]
  5. 5. Cryptography <ul><li>Public Key Cryptography </li></ul><ul><ul><li>RSA Algorithm </li></ul></ul><ul><ul><ul><li>In this system a user chooses a pair of prime numbers so large that factorizing the product is beyond all computing capabilities. </li></ul></ul></ul><ul><ul><ul><li>Stages of sending the message by this method. </li></ul></ul></ul><ul><ul><ul><ul><li>The receiver, M, distributes his public key pair. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>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 . </li></ul></ul></ul></ul>[ ]
  6. 6. Cryptography <ul><ul><ul><ul><li>c = me mod n (where e and n are Ms public key pair). </li></ul></ul></ul></ul><ul><ul><ul><ul><li>F sends the ciphertext, c , to M. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>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 . </li></ul></ul></ul></ul><ul><ul><ul><ul><li>m = cd mod n </li></ul></ul></ul></ul><ul><ul><ul><ul><li>As you can see, this process requires d , which only M knows. Another person, I, who intercepts the message, can not decrypt it. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Example: </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Let p = 5, q = 11, n = pq = 55 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>The least common multiple of ( p-1 )( q-1 ) is 20 = 22 ´ 5. </li></ul></ul></ul></ul></ul>[ ]
  7. 7. Cryptography <ul><ul><ul><ul><ul><li>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). </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Let e = 7 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>(ed -1) mod (p-1)(q-1) = 0 d = 3 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Let the plaintext message, m = b = 2 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li> The ciphertext, c = me mod n = 27 mod 55 = 18 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>To decrypt this information it is necessary to know d. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>m’ = cd mod n = 183 mod 55 = 2 The message has been successfully decrypted. </li></ul></ul></ul></ul></ul>[ ]
  8. 8. Cryptography in the &quot;Real World&quot; <ul><li>Applications of Cryptography </li></ul><ul><ul><li>military and diplomatic services </li></ul></ul><ul><ul><li>protecting confidential company information, telephone calls </li></ul></ul><ul><ul><li>Internet Business </li></ul></ul><ul><ul><li>lottery tickets </li></ul></ul>[ ]
  9. 9. Cryptanalysis <ul><li>Unlike cryptography which is a clearly defined science, cryptanalysis is as </li></ul><ul><li>much an art as it is a science. </li></ul><ul><li>Types of Cryptanalysis: The type used depends on the type of cipher and how much information the cryptanalyst has . </li></ul><ul><ul><li>Types Of Cryptanalytic Attacks </li></ul></ul><ul><ul><ul><li>A brute force attack </li></ul></ul></ul><ul><ul><ul><li>Dictionary attack </li></ul></ul></ul><ul><ul><ul><li>Ciphertext only attack </li></ul></ul></ul><ul><ul><ul><li>Chosen plaintext </li></ul></ul></ul><ul><ul><ul><li>An adaptive chosen plaintext </li></ul></ul></ul>[ ]
  10. 10. Cryptanalysis <ul><li>A Triumph of Cryptanalysis – Enigma </li></ul><ul><ul><li>What Was Enigma? </li></ul></ul><ul><ul><li>The Enigma machine consisted of a 26 letter keyboard for </li></ul></ul><ul><ul><li>input. The output was read off 26 lamps which each </li></ul></ul><ul><ul><li>corresponded to a letter. The encipherment was performed </li></ul></ul><ul><ul><li>by a device called a &quot;scrambler&quot; that was made of three </li></ul></ul><ul><ul><li>rotating wheels on a common spindle and a plug board </li></ul></ul><ul><ul><li>known as a &quot;Steckerboard&quot; that added an additional level of </li></ul></ul><ul><ul><li>security. </li></ul></ul>[ ]
  11. 11. Cryptanalysis <ul><ul><li>What Made It Possible? </li></ul></ul><ul><ul><li>With the level of sophistication of the Enigma machines it </li></ul></ul><ul><ul><li>should have been unbreakable. However, the Germans had </li></ul></ul><ul><ul><li>a number of procedural flaws which allowed the British </li></ul></ul><ul><ul><li>and Polish to break the cipher. </li></ul></ul>[ ]
  12. 12. CONCLUSION <ul><li>Military cryptography for encryption may still remain mainly symmetric key based for obvious reasons. </li></ul><ul><li>Public key cryptography would develop more in near future particularly in the context of key exchange and digital signatures. </li></ul><ul><li>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. </li></ul>[ ]
  13. 13. [ ] THANK YOU !!!

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