This document provides an overview of cryptography presented by Henry Osborne. It defines cryptography as the process of making and using codes to secure information transmission. It discusses key terms like ciphertext, plaintext, and key. It also summarizes several cipher methods: substitution cipher, transposition cipher (also known as permutation cipher), exclusive OR (XOR), and the Vernam cipher (also called the one-time pad). The presentation concludes by noting that while codes can secure information, human ingenuity will ultimately find a way to resolve any cipher.

1. CRYPTOGRAPHY
Henry Osborne
Technology Specialist
Northern Caribbean University

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
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3. Outline
 What is cryptography?
 Terminology
 Cipher Methods
 Substitution Cipher
 Transposition Cipher
 Exclusive OR
 Vernam Cipher
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4. What is Cryptography?
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5. Cryptography, which comes from the
Greek words kryptos, meaning
“hidden,” and graphein, meaning “to
write,” is the process of making and
using codes to secure the transmission
of information.
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6. Yet it may roundly be asserted that human
ingenuity cannot concoct a cipher which human
ingenuity cannot resolve.
EDGAR ALLAN POE, THE GOLD BUG
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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
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8. Cipher Methods
Image source: howstuffworks
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9. Answer: WELCOME
Image source: Gareth’s Secret Spy Academy
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10. Cipher Method: Substitution
Initial Alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ
Encryption 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
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11. Substitution Cipher cont’d
Initial Alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ
Encryption 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
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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
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13. Substitution Cipher cont’d
Plaintext A B C D E F G H I J K L MN O P Q R S T U VWX Y Z
Cipher 1 D E F G H I J K L MN O P Q R S T U VW X Y Z A B C
Cipher 2 G H I J K L MN O P Q R S T U VW X Y Z A B C D E F
Cipher 3 J K L M N O P Q R S T U VWX Y Z A B C D E F G H I
Cipher 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
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14. Cipher Method: Transposition
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15. Transposition Cipher cont’d
Key pattern: 1 -> 4, 2 -> 8, 3 -> 1, 4 -> 5, 5 -> 7, 6 -> 2, 7 -> 6, 8 -> 3
Plaintext: 00100101 01101011 10010101 01010100
Reading from right to left in the example above
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 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 0
Ciphertext 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
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16. Transposition Cipher cont’d
Key pattern: 1 -> 4, 2 -> 8, 3 -> 1, 4 -> 5, 5 -> 7, 6 -> 2, 7 -> 6, 8 -> 3
Plaintext: “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
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17. Question
What’s another name for the Transposition
Cipher?
A.Pigpen Cipher
B. Permutation Cipher
C. Caesar Cipher
D.Shift Cipher
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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 00000010
XOR Truth Table Example XOR Encryption
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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
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20. Vernam Cipher: Example
Plaintext S A C K G A U L S P A R E N O O N E
Plaintext value: 19 01 03 11 07 01 21 12 19 16 01 18 05 14 15 15 14 05
One-time pad text: F P Q R N S B I E H T Z L A C D G J
One-time pad value: 06 16 17 18 14 19 02 09 05 08 20 26 12 01 03 04 07 10
Sum of plaintext and 25 17 20 29 21 20 23 21 24 24 21 44 17 15 18 19 21 15
pad:
After modulo 03 18
subtraction:
Ciphertext: Y Q T C U T W U X X U R Q O R S U O
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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
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22. Henry Osborne
Technology Specialist
Northern Caribbean University
963-7282
henry.osborne@ncu.edu.jm @sicarii13 gplus.to/sicarii13