Cryptography, Computer Science

 Cryptography, Computer Science

  1. Chapter 1. Classical Cryptosystems
    1. Explain the Index of Coincidence (IOC).
    2. Why does the One Time Pad have Perfect Secrecy?

 

  1. Chapter 4: Cryptographic Hash Functions
    1. What is a message digest?
    2. Most cryptographic hash functions are designed to take a string of any length and convert it to a _________ length string.
    3. Cryptographic hash functions are ____________ to collisions.

 

  1. Chapter 6: Discrete logs
    1. Describe the ElGamal Discrete Log Cryptosystem.
    2. What are the three algorithms used to solve for the discrete log?
    3. Referring to Crypto System 6.1, the value of p should have at least _____ digits in order to thwart known attacks.
  2. Diffie-Helman
    1. Describe the Diffie-Hellman key exchange method. Hint – read the Wiki article. Diffie-Hellman key exchange is not in the text in an explanatory form. Show the basic math behind it.
  3. Chapter 7: digital Signature Schemes
    1. What are the six attacks on digital signature security?
    2. Refer to page 283, CS 7.1. Suppose Alice’s RSA modulus is m = 91, her encryption exponent is e = 7 and her decryption exponent is d = 31.
      1. Alice wants to sign the message x = 21. Calculate her signature.
      2. Bob receives a message-signature pair from Alice (not related to the above) and decrypts it, and gets (x=89, y=54). Does he regard the pair as likely to be authentic, or does he know that the pair has been altered? Show your work.
    3. Pseudo Random Number/Bit Generators
      1. Explain how the Blum-Blum-Shub (BBS) generator works.
      2. For Example 8.4, page 337, reproduce the first two outputs 143135 and 177671 (after i = 0, 20749), in table 8.3. Show your work.

 

Please answer according to the text book below

http://www.icst.pku.edu.cn/course/Cryptography/CryptographyTheoryandpractice%283ed%29.pdf

 

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