COMP1806: Information Security Lecture 9 – Applications of Cryptography
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Questions and Answers

What is another name for Asymmetric key encryption?

  • Private Key Encryption
  • Shared Key Encryption
  • Public Key Encryption (correct)
  • Symmetric Key Encryption

    • In Asymmetric key encryption, who is the public encryption key known to?

  • Only to the receiver
  • Known to both sender and receiver
  • Known to all (correct)
  • Only to the sender

    • What is the purpose of Bob’s private key in the RSA algorithm?

  • To generate the public key
  • To encrypt plaintext
  • To decrypt ciphertext (correct)
  • To share with the sender

    • Why is it important to agree on a key in asymmetric key encryption?

    <p>To prevent others from knowing the entire key scheme</p> Signup and view all the answers

    What is the significance of choosing large prime numbers in RSA algorithm?

    <p>To ensure security and complexity of the encryption</p> Signup and view all the answers

    What is the role of Diffie-Hellman in asymmetric key encryption?

    <p>To propose the radically different approach of public and private keys</p> Signup and view all the answers

    What is the main topic of Lecture 9 in the COMP1806 Information Security course?

    <p>Symmetric key encryption</p> Signup and view all the answers

    Which of the following is NOT a requirement for the secure use of symmetric encryption?

    <p>Sharing the key openly with all parties</p> Signup and view all the answers

    Why does symmetric key encryption fail to achieve message authentication?

    <p>Failure to keep the secret key known only to sender / receiver</p> Signup and view all the answers

    What is the estimated time required to guess the correct key for AES 256?

    <p>1.8x10^56 years</p> Signup and view all the answers

    What is the main focus of today's lecture on information security?

    <p>Fixing the limitations of symmetric key encryption using asymmetric key encryption</p> Signup and view all the answers

    What is the key factor that often fails in achieving secure use of symmetric encryption?

    <p>Inability to ensure the secret key is ONLY known to sender and receiver</p> Signup and view all the answers

    What is the main goal of cryptography?

    <p>Ensuring data confidentiality, data integrity, and data authenticity</p> Signup and view all the answers

    What does integrity ensure in the context of cryptography?

    <p>The message received is the same as the message sent</p> Signup and view all the answers

    How is authenticity accomplished in cryptography?

    <p>Using digital certificates</p> Signup and view all the answers

    What is the meaning of concealing a message by encoding it?

    <p>The sender encrypts the message using a cryptographic key</p> Signup and view all the answers

    Which technique only protects against unintentional alteration of the message in cryptography?

    <p>Using hashing to create a unique message digest</p> Signup and view all the answers

    Who can prove their identity to another without personal knowledge of their identity in cryptography?

    <p>A user or system using digital certificates</p> Signup and view all the answers

    What is the main focus of symmetric key cryptography?

    <p>Efficient encryption and decryption</p> Signup and view all the answers

    What is the main goal of a computationally secure encryption scheme?

    <p>To make it difficult to estimate the effort required to break the cipher</p> Signup and view all the answers

    In symmetric encryption, what is the relationship between plaintext length and ciphertext length?

    <p>Ciphertext is typically shorter than plaintext</p> Signup and view all the answers

    What is the purpose of the encryption function EK(P) in symmetric encryption?

    <p>To perform a one-one mapping from plaintext to ciphertext</p> Signup and view all the answers

    What characteristic should the encryption and decryption functions have in symmetric encryption?

    <p>They should have efficient algorithms</p> Signup and view all the answers

    What is the main issue that symmetric encryption aims to address?

    <p>Secure communication over insecure channels</p> Signup and view all the answers

    What is the main goal of a computationally secure encryption scheme?

    <p>To make it difficult to estimate the effort required to break the cipher</p> Signup and view all the answers

    In symmetric encryption, what is the relationship between plaintext length and ciphertext length?

    <p>Ciphertext is typically shorter than plaintext</p> Signup and view all the answers

    What is the main goal of an efficient symmetric encryption scheme?

    <p>To ensure that breaking the cipher is economically feasible</p> Signup and view all the answers

    What characteristic should the encryption and decryption functions have in symmetric encryption?

    <p>They should have efficient algorithms</p> Signup and view all the answers

    Study Notes

    Asymmetric Key Encryption

    • Also known as public-key encryption
    • Public encryption key is known to everyone
    • Purpose of Bob's private key in RSA algorithm is to decrypt the message

    Key Agreement

    • Important to agree on a key in asymmetric key encryption to ensure secure communication
    • Diffie-Hellman is a key exchange protocol used in asymmetric key encryption

    RSA Algorithm

    • Choosing large prime numbers is significant in RSA algorithm to ensure security
    • Large prime numbers make it difficult to factorize the modulus, thus ensuring security

    Symmetric Key Encryption

    • Main focus is on confidentiality and speed
    • In symmetric key encryption, the key factor that often fails is key management
    • Symmetric key encryption fails to achieve message authentication because it only provides confidentiality
    • Estimated time required to guess the correct key for AES 256 is virtually impossible

    Cryptography

    • Main goal is to provide confidentiality, integrity, and authenticity
    • Integrity ensures that the message is not modified or altered during transmission
    • Authenticity is accomplished through digital signatures
    • Concealing a message by encoding it is called encryption
    • Digital signatures only protect against unintentional alteration of the message

    Identity Verification

    • Zero-knowledge proof allows one to prove their identity to another without revealing their identity

    Symmetric Encryption Scheme

    • Main goal is to provide confidentiality and ensure that the encryption scheme is computationally secure
    • Relationship between plaintext length and ciphertext length is that the ciphertext length is equal to or greater than the plaintext length
    • Purpose of the encryption function EK(P) is to map plaintext to ciphertext
    • Encryption and decryption functions should be invertible and efficiently computable
    • Main issue that symmetric encryption aims to address is confidential transmission of data
    • Main goal of an efficient symmetric encryption scheme is to provide fast encryption and decryption

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    Test your knowledge on applications of cryptography in information security with a focus on threat actors, risk assessment, security for machine learning, designing secure systems, and more. This quiz covers the concepts discussed in Lecture 9 of the COMP1806 course.

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