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Information Cryptography Security


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This slide is presented by Mr. Zainal Hasibuan (University of Indonesia)

This slide is presented by Mr. Zainal Hasibuan (University of Indonesia)

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  • 1. Information Cryptography & Security Week 7
  • 2. Information Security & Authentication
    • Cryptography
    • Derived from the Greek word kryptos (meaning ‘hidden’)
    • The aim of Cryptography is to hide its meaning , rather than the existence of a message
    • Cryptography can be divided into 2 branches, such as:
    • 1. Transposition
    • 2. Substitution
  • 3. Cryptographic Methods
    • 1. The Rail-Fence Transposition
    • It is a transposition cryptography in which the message is written with alternate letters on separate upper and lower lines.
    • For instance: “Rail-Fence” Transposition Cryptography
    (Singh, 2000)
  • 4. Cryptographic Methods
    • 2. The Spartan scytale
    • Other transposition cryptography in the military device
    • The Scytale is a wooden staff around which a strip of leather or parchment is wound.
    • For instance: Spartan scytale
    (Singh, 2000)
  • 5. Cryptographic Methods
    • 3. The Caesar Shift Cipher
    • By substitution, Julius Caesar replaced each letter in the message with the letter that is 3 places further down the alphabet.
    • For instance: “The Caesar Cipher”
    (Singh, 2000)
  • 6. Cryptographic Methods
    • 4. The Vigenere Square cipher
    • The Vigenere cipher lies in using 26 distinct cipher alphabets.
    • For instance:
    (Singh, 2000)
  • 7. Cryptographic Methods
    • Form of transposition cipher
    (Singh, 2000)
  • 8. Exercises
    • Encrypt a message: “SBY IS OUR PRESIDENT” in the Rail-Fence transposition cipher, the Caesar cipher, and the Vigenere cipher. For Vigenere cipher, the key = “SUHENDRO”.
    • Encrypt a message: “ALO” by using Key = “TOP” in binary numbers with a simple transposition cipher.
  • 9. Older Cryptographic Machine
    • Enigma Machine
    • In the World War II, a German cryptographic machine was invented by Arthur Scherbius.
    (Singh, 2000)
  • 10. Modern Cryptography
    • Other Cryptographic methods:
    • 1. Secret Key Cryptography
    • 2. Public Key Cryptography
  • 11. Modern Cryptography
    • 1. “Secret Key” Cryptography
    • It uses a secret key such as Data Encryption Standard (DES)
    • DES is a National Institute of Standards & Technology (NIST) standard key cryptography method that uses a 56-bit key.
    • ( http:// )
    • DES lets both sender and receiver use the same key
    • to encrypt or decrypt.
  • 12. Modern Cryptography
    • 1. Process of “Secret Key” Cryptography
  • 13. Modern Cryptography
    • 2. “Public Key” Cryptography
    • It uses a private key (kept by owner) & public key is published
    • The public key uses a standard RSA (Rivest-Shamir-Adleman) Data Security, Inc. Redwood City, CA.
    • ( http:// )
    • It is more secured than a secret key cryptography
  • 14. Modern Cryptography
    • 2. Process of “Public Key” Cryptography
  • 15. Digital Signature
    • The ‘signature’ is an encrypted digest of the file (text message,
    • executable, etc)
    • Digital Signature uses hash functions to the message along
    • with a private key.
    • The message’s signature generates according to PGP
    • (Pretty Good Privacy) or SMIME (Secure Multipurpose Internet
    • Mail Extensions) standards.
    • Note: PGP is a software widely used for signing and
    • encrypting email messages.
  • 16. Digital Signature
    • Process of Digital Signature Authentication
  • 17. Digital Certificate
    • Digital Certificate (Certs) ensures if a public key belongs to the owner.
    • Digital Certificate (Certs) consists of:
    • 1. A public key
    • 2. Certificate Information
    • (i.e.: Identity of user, such as name, userID, etc)
    • 3. One or more Digital Signature
  • 18. Digital Certificate
    • Example: Digital Certificate
    Ref: Ref:
  • 19. Digital Watermark
    • A pattern of bits embedded into a file used to identify
    • the source of illegal copies.
    • If a digital watermark is placed into a master copy of
    • an audio CD, DVD, file, etc then all copies of that disc are
    • uniquely identified.
    • Example:
  • 20. References
    • Singh, S. (2000).The Code Book
    • Freedman, A. (2001). Computer Desktop Encyclopedia