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CRYPTOGRAPHYHenry OsborneTechnology SpecialistNorthern Caribbean University
Presenter Profile Education   Dip. Applied Computer Science, Jamaica Advanced Computer Systems   B.Sc. Information Scie...
Outline What is cryptography? Terminology Cipher Methods   Substitution Cipher   Transposition Cipher   Exclusive OR...
What is Cryptography?           Henry Osborne   11/11/2012   4
Cryptography, which comes from theGreek     words    kryptos,   meaning“hidden,” and graphein, meaning “towrite,” is the p...
Yet it may roundly be asserted that humaningenuity cannot concoct a cipher which humaningenuity cannot resolve.           ...
Terminology Algorithm                   Key or Cryptovariable Cipher or Crypotosystem     Keyspace Ciphertext or Cryp...
Cipher Methods                    Image source: howstuffworks    Henry Osborne               11/11/2012    8
Answer: WELCOME                  Image source: Gareth’s Secret Spy Academy                  Henry Osborne             11/1...
Cipher Method: SubstitutionInitial Alphabet    ABCDEFGHIJKLMNOPQRSTUVWXYZEncryption Alphabet D E F G H I J K L M N O P Q R...
Substitution Cipher cont’dInitial Alphabet    ABCDEFGHIJKLMNOPQRSTUVWXYZEncryption Alphabet D E F G H I J K L M N O P Q R ...
Substitution Cipher cont’d Plaintext A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Cipher 1   DEFGHIJKLMNOPQRSTUVWXY...
Substitution Cipher cont’dPlaintext   A   B   C D E F G H I J K L MN O P Q R S T U VWX Y              ZCipher 1    D   E  ...
Cipher Method: Transposition                               Henry Osborne   11/11/2012   14
Transposition Cipher cont’dKey pattern: 1 -> 4, 2 -> 8, 3 -> 1, 4 -> 5, 5 -> 7, 6 -> 2, 7 -> 6, 8 -> 3Plaintext: 00100101 ...
Transposition Cipher cont’dKey pattern: 1 -> 4, 2 -> 8, 3 -> 1, 4 -> 5, 5 -> 7, 6 -> 2, 7 -> 6, 8 -> 3Plaintext: “SACK GAU...
QuestionWhat’s another name for the TranspositionCipher?A.Pigpen CipherB. Permutation CipherC. Caesar CipherD.Shift Cipher...
Cipher Method: XOR   A   B   Y      Text Value     Binary Value   0   0   0      CAT as bits    01000011 01000001 01010100...
Vernam Cipher Also known as One-time Pad Developed by Gilbert Vernam (AT&T  engineer) in 1917 Uses a set of characters ...
Vernam Cipher: ExamplePlaintext              S    A   C   K    G   A   U   L   S   P   A     R      E      N   O   O     N...
Summary What is cryptography?   Cryptography is the process of making and using codes to    secure the transmission of i...
Henry Osborne                         Technology Specialist                     Northern Caribbean University             ...
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Cryptography

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Cryptography

  1. 1. CRYPTOGRAPHYHenry OsborneTechnology SpecialistNorthern Caribbean University
  2. 2. Presenter Profile Education  Dip. Applied Computer Science, Jamaica Advanced Computer Systems  B.Sc. Information Science, Northern Caribbean University  M.Sc. Management Information System (Security Concentration), Nova Southeastern University – candidate  Security+ candidate Professional Experience  Technology Specialist: Dept. of Computer & Information Sciences (NCU)  Instructor: NCU, VTDI  Internet Services Coordinator: Round Hill Hotel & Villas Henry Osborne 11/11/2012 2
  3. 3. Outline What is cryptography? Terminology Cipher Methods  Substitution Cipher  Transposition Cipher  Exclusive OR  Vernam Cipher Henry Osborne 11/11/2012 3
  4. 4. What is Cryptography? Henry Osborne 11/11/2012 4
  5. 5. Cryptography, which comes from theGreek words kryptos, meaning“hidden,” and graphein, meaning “towrite,” is the process of making andusing codes to secure the transmissionof information. Henry Osborne 11/11/2012 5
  6. 6. Yet it may roundly be asserted that humaningenuity cannot concoct a cipher which humaningenuity cannot resolve. EDGAR ALLAN POE, THE GOLD BUG Henry Osborne 11/11/2012 6
  7. 7. Terminology Algorithm  Key or Cryptovariable Cipher or Crypotosystem  Keyspace Ciphertext or Cryptogram  Link Encryption Code  Plaintext or Cleartext Decode  Steganography Decipher  Work factor Encipher Henry Osborne 11/11/2012 7
  8. 8. Cipher Methods Image source: howstuffworks Henry Osborne 11/11/2012 8
  9. 9. Answer: WELCOME Image source: Gareth’s Secret Spy Academy Henry Osborne 11/11/2012 9
  10. 10. Cipher Method: SubstitutionInitial Alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZEncryption Alphabet D E F G H I J K L M N O P Q R S T U V W X Y Z A B C This type of substitution is based on a monoalphabetic substitution, because it only uses one alphabet. Plaintext M O M Ciphertext P R P Henry Osborne 11/11/2012 10
  11. 11. Substitution Cipher cont’dInitial Alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZEncryption Alphabet D E F G H I J K L M N O P Q R S T U V W X Y Z A B C Plaintext F A C E Ciphertext I D F H Henry Osborne 11/11/2012 11
  12. 12. Substitution Cipher cont’d Plaintext A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Cipher 1 DEFGHIJKLMNOPQRSTUVWXYZABC Cipher 2 GHIJKLMNOPQRSTUVWXYZABCDEF Cipher 3 JKLMNOPQRSTUVWXYZABCDEFGHI Cipher 4 MNOPQRSTUVWXYZABCDEFGHIJKL More advanced substitution ciphers use two or more alphabets, and are referred to as polyalphabetic substitutions. Plaintext T E X T Ciphertext W K G F Henry Osborne 11/11/2012 12
  13. 13. Substitution Cipher cont’dPlaintext A B C D E F G H I J K L MN O P Q R S T U VWX Y ZCipher 1 D E F G H I J K L MN O P Q R S T U VW X Y Z A B CCipher 2 G H I J K L MN O P Q R S T U VW X Y Z A B C D E FCipher 3 J K L M N O P Q R S T U VWX Y Z A B C D E F G H ICipher 4 M N O P Q R S T U VWX Y Z A B C D E F G H I J K L Plaintext P A S S C T T Ciphertext S G B E F Z C Henry Osborne 11/11/2012 13
  14. 14. Cipher Method: Transposition Henry Osborne 11/11/2012 14
  15. 15. Transposition Cipher cont’dKey pattern: 1 -> 4, 2 -> 8, 3 -> 1, 4 -> 5, 5 -> 7, 6 -> 2, 7 -> 6, 8 -> 3Plaintext: 00100101 01101011 10010101 01010100 Reading from right to left in the example aboveBit Locations 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1Plaintext 0 0 1 0 0 1 0 1 0 1 1 0 1 0 1 1 1 0 0 1 0 1 0 1 0 1 0 1 0 1 0 0Ciphertext 0 0 0 0 1 0 1 1 1 0 1 1 1 0 1 0 0 1 0 0 1 1 0 1 0 1 1 0 0 0 0 1 Henry Osborne 11/11/2012 15
  16. 16. Transposition Cipher cont’dKey pattern: 1 -> 4, 2 -> 8, 3 -> 1, 4 -> 5, 5 -> 7, 6 -> 2, 7 -> 6, 8 -> 3Plaintext: “SACK GAUL SPARE NO ONE” Bit Locations 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 Plaintext S A C K GAU L S P A R E NOON E Ciphertext UKAG L S CAOR P EOS AN E N Henry Osborne 11/11/2012 16
  17. 17. QuestionWhat’s another name for the TranspositionCipher?A.Pigpen CipherB. Permutation CipherC. Caesar CipherD.Shift Cipher Henry Osborne 11/11/2012 17
  18. 18. Cipher Method: XOR A B Y Text Value Binary Value 0 0 0 CAT as bits 01000011 01000001 01010100 0 1 1 VVV as bits 01010110 01010110 01010110 1 0 1 1 1 0 Cipher 00010101 00010111 00000010XOR Truth Table Example XOR Encryption Henry Osborne 11/11/2012 18
  19. 19. Vernam Cipher Also known as One-time Pad Developed by Gilbert Vernam (AT&T engineer) in 1917 Uses a set of characters only one time for each encryption process To use a one-time pad, you need 2 copies of the "pad" which is a block of random data equal in length to the message you wish to encode. A RUSSIAN ONE-TIME PAD, CAPTURED BY MI5 Image source: http://www.ranum.com/security/computer_security/papers/otp-faq/otp.jpg Henry Osborne 11/11/2012 19
  20. 20. Vernam Cipher: ExamplePlaintext S A C K G A U L S P A R E N O O N EPlaintext value: 19 01 03 11 07 01 21 12 19 16 01 18 05 14 15 15 14 05One-time pad text: F P Q R N S B I E H T Z L A C D G JOne-time pad value: 06 16 17 18 14 19 02 09 05 08 20 26 12 01 03 04 07 10Sum of plaintext and 25 17 20 29 21 20 23 21 24 24 21 44 17 15 18 19 21 15pad:After modulo 03 18subtraction:Ciphertext: Y Q T C U T W U X X U R Q O R S U O Henry Osborne 11/11/2012 20
  21. 21. Summary What is cryptography?  Cryptography is the process of making and using codes to secure the transmission of information. Key Terms  Ciphertext, Plaintext, Key, etc Cipher Methods  Substitution Cipher  Transposition Cipher (or permutation cipher)  Exclusive OR  Vernam Cipher Henry Osborne 11/11/2012 21
  22. 22. Henry Osborne Technology Specialist Northern Caribbean University 963-7282henry.osborne@ncu.edu.jm @sicarii13 gplus.to/sicarii13

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