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Cryptography Cryptography

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... cs.usask.ca/resources/tutorials/csconcepts/1999_3/lessons/L3/SimpleEncrypti on.html ... RSA Laboratories. 2004. http://www.rsasecurity.com/rsalabs/node.asp?id=2155 ... – PowerPoint PPT presentation

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Title: Cryptography Cryptography


1
CryptographyCryptography
  • Brought to you by
  • Shannon Burke

2
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

3
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.

4
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.

5
Symmetric Cryptosystem!
Saflslkafskflsakflsdfjfdlkajfkdjafksjdljkasldskf
jfffffffffffffffffffffffffffffkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkk
6
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

7
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.

8
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

9
How its works!!!!
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
kkkkkkkkkkkkkkkk
10
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

11
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?

12
Your Grade!!!
  • Everyone Passed!!!!!
  • Thanks for your attention and participation!!!!!!

13
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
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