Hash Applications
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Which of the following is NOT a solution for securely storing passwords using hash functions?

  • Using salt to store hashed password in a database
  • Direct storage of userid and password in a database table
  • Storing plaintext password in a database (correct)
  • Storing hashed password in a database

    • What is the risk associated with direct storage of userid and password in a database table?

  • If an attacker gains access to the database, they can only impersonate the user whose credentials they stole
  • If an attacker gains access to the database, they can only view the user's credentials
  • If an attacker gains access to the database, they can impersonate any user (correct)
  • There is no risk associated with direct storage of userid and password in a database table

    • What is the issue with storing hashed password in a database without using salt?

  • There is no issue with storing hashed password in a database without using salt
  • If an attacker gains access to the database, they can impersonate any user
  • If an attacker gains access to the database, they can use precomputed lookup tables of hashes of frequently used passwords to find matches (correct)
  • If an attacker gains access to the database, they can only view the user's credentials

    • What is the recommended solution for securely storing passwords using hash functions?

    <p>Using salt to store hashed password in a database</p> Signup and view all the answers

    What is a blockchain?

    <p>A distributed ledger for storing cryptocurrency transactions</p> Signup and view all the answers

    What makes a blockchain immutable and secure?

    <p>Any changes to a block's content would require altering all subsequent blocks</p> Signup and view all the answers

    What is a proof-of-work scheme?

    <p>A scheme employed in Bitcoin and anti-spam systems that uses hash functions to ensure that creating a valid message requires a certain amount of computing resources</p> Signup and view all the answers

    What is the purpose of a nonce in proof-of-work schemes?

    <p>To append to a file or message and compute a hash</p> Signup and view all the answers

    What is the role of a miner in Bitcoin mining?

    <p>To check new transactions, build a new block, compute a proof-of-work, and write the successful nonce into the block</p> Signup and view all the answers

    What is the purpose of a proof-of-work nonce in anti-spam schemes?

    <p>To produce a nonce that satisfies the proof-of-work condition to send a message</p> Signup and view all the answers

    What happens to emails without proof-of-work in anti-spam schemes?

    <p>They are rejected by the receiver</p> Signup and view all the answers

    What is the purpose of adjusting the required pattern of the hash code in proof-of-work schemes?

    <p>To adjust the difficulty of proof-of-work</p> Signup and view all the answers

    Which of the following is a risk associated with storing user credentials directly in a database table?

    <p>An attacker can impersonate any user</p> Signup and view all the answers

    What is the recommended solution for securely storing passwords using hash functions?

    <p>Using salt</p> Signup and view all the answers

    What is the purpose of a salt in password storage using hash functions?

    <p>To add randomness to the hash function</p> Signup and view all the answers

    What is a blockchain?

    <p>A distributed ledger</p> Signup and view all the answers

    What is the difference between permissionless and permissioned blockchain?

    <p>Permissionless blockchain allows anybody to join</p> Signup and view all the answers

    What is the purpose of proof-of-work in Bitcoin and anti-spam systems?

    <p>To prevent spam emails from being sent</p> Signup and view all the answers

    What is the role of a miner in Bitcoin mining?

    <p>To build a new block and compute a proof-of-work</p> Signup and view all the answers

    What is the purpose of a nonce in proof-of-work schemes?

    <p>To add randomness to the hash function</p> Signup and view all the answers

    What happens if an email sender does not provide a proof-of-work nonce in anti-spam schemes?

    <p>The email is rejected by the receiver</p> Signup and view all the answers

    What is the purpose of adjusting the required pattern of the hash code in proof-of-work schemes?

    <p>To make it more difficult for miners to validate transactions</p> Signup and view all the answers

    What is the difference between direct storage and storing hashed password in password storage using hash functions?

    <p>Storing hashed password is more secure</p> Signup and view all the answers

    What is the purpose of a distributed ledger in blockchain technology?

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

    What are the different levels of knowledge an attacker can have when trying to break a cipher?

    <p>Ciphertext only, known plaintext, chosen plaintext, chosen ciphertext, samples of previous signatures or message authentication codes.</p> Signup and view all the answers

    What does it mean to 'break' a cryptosystem?

    <p>Finding the plaintext, the key, creating a digital signature or creating a message authentication code.</p> Signup and view all the answers

    Does obtaining some partial information about the plaintext/key count as 'breaking' the cryptosystem?

    <p>It depends on the definition of security being used.</p> Signup and view all the answers

    What is computational security?

    <p>It means that breaking the cipher is unfeasible (too time/resource consuming) based on the currently available algorithms and computing power.</p> Signup and view all the answers

    What is unconditional security?

    <p>It means that breaking the cipher is impossible (even with unlimited time/resources).</p> Signup and view all the answers

    What is perfect secrecy?

    <p>It means that the ciphertext leaks no information about the plaintext (except the length); guessing the plaintext has the same chances of success after having seen the ciphertext as it had before seeing it.</p> Signup and view all the answers

    What is provable security?

    <p>It means that there is no efficient algorithm that can be used by the attacker to succeed with reasonably high probability.</p> Signup and view all the answers

    For which type of cryptography are there security proofs?

    <p>Mainly public key cryptography.</p> Signup and view all the answers

    Is there provable security for symmetric cryptography?

    <p>No.</p> Signup and view all the answers

    What do the other ciphers in use today have in terms of security?

    <p>Computational security only in the sense that no attack has succeeded in a reasonable amount of time. However, there is no proof that no efficient attack will be found.</p> Signup and view all the answers

    What is the one-time pad?

    <p>A cipher that has perfect secrecy.</p> Signup and view all the answers

    Why is the one-time pad not used in practice?

    <p>Because it is expensive.</p> Signup and view all the answers

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