Maintaining Confidentiality

• One time pad (OTP)
  • length of key equal to message length
  • c = m XOR k
  • c XOR k = m
  • perfect secrecy
  • severe key distribution problems
• Shared secret key
  • c = E(m,k).
  • D(c,k) = m
  • requires key distribution
  • vulnerable to exhaustive key search
• Private / public key
  • Key generator creates Ek, Dk
  • c = E(m, Ek)
  • D(c, Dk) = m
  • Computationally expensive

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 Last change: Friday, June 6, 2003 3:09 pm
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