# Exercises
These questions are for you to go over what you learned in this chapter.

**Using the online [SHA-256 hash generator](https://www.movable-type.co.uk/scripts/sha256.html),
calculate the SHA-256 hash of the following messages:**
* 42
* 43
* Hello World
* Hello World!

What pattern do you notice?
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**State the three properties of good hash functions**
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**What are two implementations of PPC and what are their respective advantages/disadvantages?**
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**Briefly explain how we can generate a merkle tree**
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**Why is randomness important in cryptography?**
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**How does Blockchain primarily use cryptography?**
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**Bill says he can use ECDSA to securely exchange messages with you. 
Is Bill correct? Why or why not?**
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**Are most blockchain project anonymous? If not then what are they?**
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**Briefly explain how Proof-of-Work utilizes hashing.**
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**How is the valid chain determined in PoW?**
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