Encryption and Decryption Quiz
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Questions and Answers

What term is used to describe the process of converting plaintext to ciphertext?

  • Decoding
  • Decryption
  • Encryption (correct)
  • Encapsulation
  • What is a block cipher?

  • A cipher that encrypts data bit by bit
  • An outdated encryption method
  • A system used for security management
  • A method that transforms messages into blocks for encryption (correct)
  • What type of crypto system is used when both the sender and receiver utilize the same key?

  • Symmetric key crypto system (correct)
  • Asymmetric key crypto system
  • Hybrid key crypto system
  • Public-key crypto system
  • Which of the following cryptographic algorithms uses 64-bit blocks and is a symmetric encryption method?

    <p>DES</p> Signup and view all the answers

    What is the key size utilized by a DES system?

    <p>56 bit</p> Signup and view all the answers

    What is a significant disadvantage of symmetric encryption systems?

    <p>The secure transmission of the secret key could be compromised</p> Signup and view all the answers

    Which statement is most accurate regarding newly developed encryption methods?

    <p>They should be avoided until proven</p> Signup and view all the answers

    Certified encryption methods are best described as:

    <p>Reliant on the level and source of certification</p> Signup and view all the answers

    What will be the value of Phi if using the RSA algorithm with prime numbers p = 5 and q = 11?

    <p>14</p> Signup and view all the answers

    In asymmetric encryption, which key does Carol use to encrypt a message intended for Bob?

    <p>Bob’s Public Key</p> Signup and view all the answers

    What key will Bob use to decrypt the message once Carol has encrypted it for confidentiality?

    <p>Bob’s Private Key</p> Signup and view all the answers

    How many private and public keys are used in a classroom of 30 students and a professor if every student submits an encrypted assignment?

    <p>31 public and 30 private</p> Signup and view all the answers

    Why is public-key encryption generally considered more secure than symmetric encryption?

    <p>It uses two keys</p> Signup and view all the answers

    The RSA algorithm is primarily used in which of the following applications?

    <p>Digital signatures</p> Signup and view all the answers

    The effectiveness of the Diffie-Hellman algorithm relies on what mathematical concept?

    <p>Discrete logarithms</p> Signup and view all the answers

    What is the most widely used public-key cryptosystem?

    <p>RSA</p> Signup and view all the answers

    In an asymmetric cryptography system, who uses the private key to decrypt ciphertext?

    <p>Receiver</p> Signup and view all the answers

    What type of document does a Certification Authority issue to bind a subscriber's name to a public key?

    <p>Digital certificate</p> Signup and view all the answers

    The primary objective of a hash function is to ensure what?

    <p>Data integrity</p> Signup and view all the answers

    Which family of cryptographic hash functions is the most widely used?

    <p>Secure Hash Algorithm (SHA)</p> Signup and view all the answers

    In the context of digital signatures, the hash value of a message is encrypted with which key?

    <p>Sender's private key</p> Signup and view all the answers

    What guarantees does a digital signature provide?

    <p>Both the integrity and source of the message</p> Signup and view all the answers

    When comparing hash values to verify a message's integrity, what indicates that the message has not been altered?

    <p>Hash values are equal</p> Signup and view all the answers

    What key does a sender use to digitally sign a hash before sending it?

    <p>Sender's private key</p> Signup and view all the answers

    Study Notes

    Encryption and Decryption

    • Deciphering/Decryption: The process of converting ciphertext back to plaintext.
    • Symmetric Key Cryptosystem: Uses the same key for both encryption and decryption.

    Symmetric Key Encryption

    • Block Cipher: Encrypts data in blocks, often 8 or 16 bits, transforming each block with a key.
    • DES (Data Encryption Standard): A classic symmetric cryptosystem using 64-bit blocks with a 56-bit key.
    • Disadvantage of Symmetric Encryption: The difficulty of securely transmitting the secret key.

    Choosing Encryption Methods

    • Consider the vendor's claims carefully: Don't assume advertised "unbreakable" methods are truly reliable.
    • New Encryption Methods: Use with caution until they have been thoroughly tested and proven.
    • Certified Encryption Methods: Check the level and source of certification to ensure they are trustworthy.

    Asymmetric Key Encryption

    • Public-Key Cryptosystem: Uses two keys: a public key for encryption and a private key for decryption.
    • RSA: The most widely used public-key cryptosystem.
    • Diffie-Hellman Algorithm: Dependent on the difficulty of computing discrete logarithms for its security.
    • RSA Modulus (N): Calculated by multiplying two large prime numbers (p and q). Finding the prime numbers from N is virtually impossible.
    • Confidentiality with Asymmetric Encryption: The sender (Carol) uses the receiver's (Bob's) public key to encrypt messages.
    • Decryption with Asymmetric Encryption: The receiver (Bob) uses their private key to decrypt the message.

    Digital Signatures

    • Public Key Cryptosystem for Digital Signatures: The sender uses their private key to sign the hash of the message before sending it.
    • Hash Function's Purpose: Ensures data integrity and authentication.
    • Purpose of a Digital Certificate: Authenticates the public key.
    • Verification of Digital Signatures: Upon receiving a message, the receiver compares the hash value of the message to the original hash value in the digital signature.
    • Equal Hash Values: Indicate that the message has not been altered.

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    Description

    Test your knowledge on encryption and decryption techniques, including symmetric and asymmetric key systems. This quiz covers important concepts like block ciphers, DES, and the selection of encryption methods. Understand the advantages and disadvantages of various encryption techniques.

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