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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Introduction to Cryptography presentation used for CTT+ video exam....

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  • NCU -> Data Security, Java, C++, Networking, PC Repair, Computer ApplicationsVTDI -> Web Programming
  • If you have any relevant questions during the presentation please feel free to ask….
  • In light of the increase in computer usage and online activities, the need for the safe and secure transmission of data is paramount. This is where cryptography comes into play.Today, many common IT tools use embedded encryption technologies to protect sensitive information within applications. For example, all the popular Web browsers use built-in encryption features to enable secure e-commerce, such as online banking and Web shopping.
  • In the study of cryptography there some terms you will need to be acquainted with….Definitions are on the handout that you received earlier….Ciphertextor cryptogram: The encoded message resulting from an encryptionPlaintext or cleartext: The original unencrypted message, or a message that has been successfully decrypted
  • The Pigpen cipher (sometimes called the Masonic cipher or Freemason's cipher) is a simple substitution cipher exchanging letters for symbols based on a grid (or the "pigpen") surrounding it.
  • To use a substitution cipher, you substitute one value for another, for example a letter in the alphabet with the letter three values to the right. Or you can substitute one bit for another bit that is four places to its left.Within this substitution scheme, the plaintext MOM would be encrypted into the ciphertext PRP.
  • The plaintext FACE would be encrypted into the ciphertext IDFH.
  • Encoding the word TEXT with this cipher yields the ciphertextWKGF
  • Like the substitution operation, the transposition cipher is simple to understand, but it can, if properly used, produce ciphertext that is difficult to decipher.The transposition cipher (or permutation cipher) simply rearranges the values within a block to create the ciphertext. This can be done at the bit level or at the byte (character) level.
  • The first bit of plaintext (position 1 of the first byte) becomes the fourth bit (in position 4) of the first byte of the ciphertext. Similarly, the second bit of the plaintext (position 2) becomes the eighth bit (position 8) of the cipher-text, and so on.
  • To examine further how this transposition key works, look at its effects on a plaintext message comprised of letters instead of bits. Replacing the 8-bit block of plaintext with the example plaintext message presented earlier, “SACK GAUL SPARE NO ONE,” yields the following:
  • Permutation Cipher
  • The exclusive OR operation (XOR) is a function of Boolean algebra in which two bits are compared, and if the two bits are identical, the result is a binary 0. If the two bits are not the same, the result is a binary 1.To see how XOR works, consider an example in which the plaintext is the word “CAT.” The ASCII binary representation of the plaintext is “01000011 01000001 01010100”. In order to encrypt the plaintext, a key value should be selected. In this case, the bit pattern for the letter “V” (01010110) is used, and is repeated for each character to be encrypted, written left to right. Performing the XOR operation on the two bit streams (the plaintext and the key) produces the cipher as shown.
  • The pad in the name comes from the days of manual encryption and decryption when the key values for each ciphering session were prepared by hand and bound into an easy-to-use form—that is, a pad of paper.A one-time pad is a cryptosystem invented by Vernam. It's a very simple system and is unbreakable if used correctly.
  • Using the pad values and the ciphertext, the decryption process works as follows: “Y” becomes the number 25, from which we subtract the pad value for the first letter of the message, 06. This yields a value of 19, or the letter “S”. Where the ciphertext letter is “C” and the pad value is 18. Subtracting 18 from 3 yields negative 15. Since modulo 26 is employed, which requires that all numbers are in the range of 1–26, you must add 26 to the negative 15. This operations gives a sum of 11, which means that fourth letter of the message is “K.”
  • To use a substitution cipher, you substitute one value for another, or you can substitute one bit for another bit x places to its left or right.The transposition cipher simply rearranges the values within a blockThe exclusive OR (XOR) operation is a function of Boolean algebra in which two bits are compared, and if the two bits are identical, the result is a binary 0
  • 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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