Cryptography and Information Theory Basics
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Questions and Answers

What is the main drawback of fixed dictionary coding compared to adaptive coding?

  • It is faster in encoding and decoding processes.
  • It requires constant updates based on input.
  • It uses variable-length codes for symbols.
  • It may lead to inefficient data representation. (correct)
  • Which of the following correctly differentiates between entropy and conditional entropy?

  • Both concepts represent the same measure of information.
  • Entropy measures the uncertainty of a random variable, while conditional entropy measures the uncertainty given another variable. (correct)
  • Conditional entropy only applies to discrete variables.
  • Entropy is always greater than conditional entropy.
  • Which of the following describes a disadvantage of symmetric ciphers?

  • They require more computational resources than asymmetric ciphers.
  • They are less secure than asymmetric ciphers in all scenarios.
  • They are generally much slower than asymmetric ciphers.
  • Key distribution becomes more complex as the number of users increases. (correct)
  • In the context of the Data Encryption Standard (DES), what is the purpose of padding?

    <p>To increase the size of the plaintext to a fixed length.</p> Signup and view all the answers

    Which of the following statements about Mono-alphabetic ciphers is correct?

    <p>They substitute each letter with a fixed counterpart for the entire message.</p> Signup and view all the answers

    What does the process of key agreement in the RSA algorithm involve?

    <p>The two parties establish a shared secret without directly exchanging keys.</p> Signup and view all the answers

    Which technique is primarily utilized by Caesar ciphers?

    <p>Rotation of letters by a specified number.</p> Signup and view all the answers

    Which property differentiates a block cipher from a stream cipher?

    <p>Block ciphers encrypt data in fixed-size blocks, while stream ciphers encrypt data as a continuous stream.</p> Signup and view all the answers

    Study Notes

    Fixed Dictionary Coding vs. Adaptive Coding

    • Fixed dictionary coding uses a predefined codebook, limiting its adaptability to changing data patterns.
    • Adaptive coding dynamically adjusts its codebook based on the observed data frequencies, offering better compression for frequently occurring patterns.

    Entropy vs. Conditional Entropy

    • Entropy measures the uncertainty of a random variable, quantifying the average information content.
    • Conditional entropy quantifies the uncertainty of a random variable given the knowledge of another variable, representing the remaining uncertainty after considering the relationship.

    Disadvantage of Symmetric Ciphers

    • A major drawback of symmetric ciphers is the requirement for secure key distribution, as the same key is used for both encryption and decryption.

    Padding in DES

    • Padding in DES ensures that the plaintext block aligns with the block size of the cipher by adding extra bits, preventing information leakage and enhancing security.

    Mono-alphabetic Ciphers

    • Mono-alphabetic ciphers use a single substitution alphabet, making them vulnerable to frequency analysis, which can reveal the underlying plaintext.

    Key Agreement in RSA

    • Key agreement in RSA involves the exchange of public keys between parties to establish secure communication.

    Technique of Caesar Ciphers

    • Caesar ciphers utilize a simple substitution technique, shifting each letter in the plaintext by a fixed number of positions in the alphabet.

    Block Cipher vs. Stream Cipher

    • Block ciphers process data in fixed-size blocks, encrypting each block independently, while stream ciphers encrypt individual bits or bytes in continuous streams.

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    Cryptography Exam Questions PDF

    Description

    This quiz covers fundamental concepts in cryptography and information theory, including parity, entropy, types of coding, and various encryption techniques. Participants will explore the properties of linear block codes, symmetric ciphers, and the significance of secure communication. Get ready to test your knowledge on these critical topics!

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