> For the complete documentation index, see [llms.txt](https://davidjosearaujo.gitbook.io/online-courses/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://davidjosearaujo.gitbook.io/online-courses/blockchain-security/fundamentals-of-blockchain-security/quiz.md).

# Quiz

## Question 1

Which of the following are uses for hash functions in blockchain?

<details>

<summary>Solution</summary>

* Block "chains" tying blocks together
* Merkle trees holding the transactions within a block

</details>

## Question 2

Which of the following are promises of blockchain technology?

<details>

<summary>Solution</summary>

* Immutability
* Decentralization

</details>

## Question 3

A hash function where similar inputs produce similar outputs break collision resistance because it violates what?

<details>

<summary>Solution</summary>

Non-locality

</details>

## Question 4

Which of the following properties of hash functions is essential to protecting against a single block being forged without changing the values of future blocks?

<details>

<summary>Solution</summary>

* **Second preimage resistance**

Second preimage resistance means that it is impossible to find another hash input that produces the same output as an existing hash input. If an attacker can find another version of a block with the same hash, then they can replace that block without detection.

</details>