Cryptography Cryptography

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CryptographyCryptography

• Brought to you by
• Shannon Burke

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Brief History of Cryptography!!!!

• What is Cryptography?
• Science of writing secret code
• The first use of cryptography in 1900 B.C.
• Used by Egyptian scribe
• Some experts say it appeared right after writing
  was invented

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Cryptography Broken Down!!!

• Two kinds of cryptosystems
• Symmetric
• Uses the same key (the secret key) to encrypt and
  decrypt a message.
• Asymmetric
• Uses one key (the public key) to encrypt a
  message and a different key (the private key) to
  decrypt the message.

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Symmetric Cryptosystem!

• The message
• The sender and receiver know and use the same
  secret key.
• The sender uses the secret key to encrypt the
  message.
• The receiver uses the same secret key to decrypt
  the message.

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Symmetric Cryptosystem!
Saflslkafskflsakflsdfjfdlkajfkdjafksjdljkasldskf
jfffffffffffffffffffffffffffffkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkk
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Symmetric Challenge!

• Main challenge
• Agreeing on the key while maintaining secrecy.
• Trusting a phone system or some transmission
  medium.
• The interceptor can read, modify, and forge all
  messages

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Key Management!!!

• Key management
• The generation, transmission, and storage of a
  key.
• All cryptosystems must deal with key management
  issues
• Because all keys must remain secret there is
  often difficulty providing secure key management.

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Introduction of the Public Key!!!

• Created to solve key management problems.
• Created by Whitfield Diffie and Martin Hellman in
  1976.
• Also called asymmetric system.
• Encryption key public key
• Decryption key private key

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How its works!!!!
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkk
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Lets see some examples!!!!

• Click here to experiment with different
  encryption methods.
• http//www.cs.usask.ca/resources/tutorials/csconce
  pts/1999_3/lessons/L3/SimpleEncryption.html

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A Little Quiz to Test What You Learned!!!

• 1.)What are the two different types of
  cryptosystems?
• 2.)What is the difference between the two
  systems?
• Which system was created as a result of
  difficulties of the other? What was the
  difficulty?

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Your Grade!!!

• Everyone Passed!!!!!
• Thanks for your attention and participation!!!!!!

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Bibliography!!!!

• Cryptography World. 2002. http//www.cryptographyw
  orld.com/index.htm
• Kessler, Gary. An Overview of Cryptography. May
  1998. http//www.garykessler.net/library/crypto.ht
  ml
• Litterio, Francis. Cryptography.
  http//world.std.com/franl/crypto.html
• RSA Laboratories. 2004. http//www.rsasecurity.com
  /rsalabs/node.asp?id2155