Lecture on 11 December 2018 Cryptography Steganography Blockchain for Beginners Elective course from the Faculty of Information Technology, Thai - Nichi Institute of Technology, Bangkok for undergraduate students. #BlockchainTNI2018

1. Blockchain Technology
Week 5
Unit III – Cryptography and Steganography
Ferdin Joe John Joseph, PhD
Faculty of Information Technology
Thai-Nichi Institute of Technology, Bangkok
Venue: D603

2. Week 5 – Unit III
Agenda
• Cryptography
• Steganography
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3. Blockchain
Database
Distributed
System
Security
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4. Cryptography
Security
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5. What is Cryptography?
“The art and science of concealing the messages to introduce secrecy
in information security is recognized as cryptography.”
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6. Introduction to Computer Security
Confidentiality
AvailabilityIntegrity
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7. Introduction to Computer Security
Confidentiality
•Data Confidentiality
•Privacy
Integrity
•Data Integrity
•System Integrity
Availability
•Availability
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8. Security Attacks
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9. Terminologies
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A message is plaintext (sometimes called clear text). The process of
disguising a message in such a way as to hide its substance is
encryption. An encrypted message is ciphertext. The process of turning
ciphertext back into plaintext is decryption.

10. Cryptography Vs Cryptanalysis
While cryptography is the science of securing data, cryptanalysis is the
science of analyzing and breaking secure communication. Classical
cryptanalysis involves an interesting combination of analytical
reasoning, application of mathematical tools, pattern finding, patience,
determination, and luck. Cryptanalysts are also called attackers.
Cryptology embraces both cryptography and cryptanalysis.
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11. Nomenclature
Cryptography = Krypto + Graphy
Origin: Greek
Krypto: Secret
Graphy: Writing
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12. Ancient Cryptography: Caesar Cipher
Activity
With the given cipher, perform encryption of your first name and last
name.
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Plain
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
G H I J K L M N O P Q R S T U V W X Y Z A B C D E F
B L O C K C H A I N T E C H N O L O G Y
H R U I Q I N G O T Z K I N T U R U M E

13. Types of Cryptography
• Symmetric Key Cryptography
• Asymmetric Key Cryptography
• Hash Functions
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14. Symmetric Key Cryptography
• Also known as Secret Key Cryptography or Conventional Cryptography
or Private Key Cryptography
• Symmetric Key Cryptography is an encryption system in which the
sender and receiver of a message share a single, common key that is
used to encrypt and decrypt the message.
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15. Symmetric Key Cryptography
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16. Symmetric Key Cryptography - Issues
• Symmetric-key systems are simpler and faster; their main drawback is
that the two parties must somehow exchange the key in a secure way
and keep it secure after that.
• Key Management caused nightmare for the parties using the
symmetric key cryptography. They were worried about how to get the
keys safely and securely across to all users so that the decryption of
the message would be possible. This gave the chance for third parties
to intercept the keys in transit to decode the top-secret messages.
Thus, if the key was compromised, the entire coding system was
compromised and a “Secret” would no longer remain a “Secret”.
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17. Faculty of Information Technology, Thai-Nichi Institute of
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18. Asymmetric Key Cryptography
Asymmetric cryptography , also known as Public-key cryptography,
refers to a cryptographic algorithm which requires two separate keys,
one of which is private and one of which is public. The public key is
used to encrypt the message and the private one is used to decrypt the
message.
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19. Asymmetric Key Cryptography
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20. Hash Functions
A cryptographic hash function is a hash function that takes an arbitrary
block of data and returns a fixed-size bit string, the cryptographic hash
value, such that any (accidental or intentional) change to the data will
(with very high probability) change the hash value. The data to be
encoded are often called the message, and the hash value is sometimes
called the message digest or simply digest.
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21. Hash Functions
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22. Hash Functions
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23. Activity
• https://aesencryption.net/
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24. Week 4 – Unit II
Agenda
• Cryptography
• Steganography
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25. Definition
• Art and science of information hiding in an ordinary file and
extraction of information at its destination.
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26. Visuals
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27. Steganography process
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28. Types of Steganography
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Steganography
Text Image Video Audio

29. Steganography - Pragmatics
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30. Demonstration
Blockchain hashing
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31. Next Week
• Role of Cryptography in Blockchain
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