Hash Applications

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?

Using salt to store hashed password in a database (C) Signup and view all the answers

What is a blockchain?

A distributed ledger for storing cryptocurrency transactions (A) Signup and view all the answers

What makes a blockchain immutable and secure?

Any changes to a block's content would require altering all subsequent blocks (C) Signup and view all the answers

What is a proof-of-work scheme?

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 (A) Signup and view all the answers

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

To append to a file or message and compute a hash (D) Signup and view all the answers

What is the role of a miner in Bitcoin mining?

To check new transactions, build a new block, compute a proof-of-work, and write the successful nonce into the block (D) Signup and view all the answers

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

To produce a nonce that satisfies the proof-of-work condition to send a message (A) Signup and view all the answers

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

They are rejected by the receiver (A) Signup and view all the answers

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

To adjust the difficulty of proof-of-work (B) Signup and view all the answers

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

An attacker can impersonate any user (D) Signup and view all the answers

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

Using salt (D) Signup and view all the answers

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

To add randomness to the hash function (D) Signup and view all the answers

What is a blockchain?

A distributed ledger (A) Signup and view all the answers

What is the difference between permissionless and permissioned blockchain?

Permissionless blockchain allows anybody to join (D) Signup and view all the answers

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

To prevent spam emails from being sent (B) Signup and view all the answers

What is the role of a miner in Bitcoin mining?

To build a new block and compute a proof-of-work (B) Signup and view all the answers

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

To add randomness to the hash function (C) Signup and view all the answers

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

The email is rejected by the receiver (A) Signup and view all the answers

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

To make it more difficult for miners to validate transactions (A) Signup and view all the answers

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

Storing hashed password is more secure (B) Signup and view all the answers

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

To ensure the security of the blockchain (A) Signup and view all the answers

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

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

What does it mean to 'break' a cryptosystem?

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

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

It depends on the definition of security being used. Signup and view all the answers

What is computational security?

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

What is unconditional security?

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

What is perfect secrecy?

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. Signup and view all the answers

What is provable security?

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

For which type of cryptography are there security proofs?

Mainly public key cryptography. Signup and view all the answers

Is there provable security for symmetric cryptography?

No. Signup and view all the answers

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

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. Signup and view all the answers

What is the one-time pad?

A cipher that has perfect secrecy. Signup and view all the answers

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

Because it is expensive. Signup and view all the answers

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Questions and Answers

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

What is the 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?

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

What is a blockchain?

What makes a blockchain immutable and secure?

What is a proof-of-work scheme?

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

What is the role of a miner in Bitcoin mining?

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

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

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

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

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

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

What is a blockchain?

What is the difference between permissionless and permissioned blockchain?

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

What is the role of a miner in Bitcoin mining?

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

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

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

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

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

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

What does it mean to 'break' a cryptosystem?

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

What is computational security?

What is unconditional security?

What is perfect secrecy?

What is provable security?

For which type of cryptography are there security proofs?

Is there provable security for symmetric cryptography?

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

What is the one-time pad?

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

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