SHA-1 is the most commonly used SHA algorithm, and produces a ______-byte hash value(size).

Correct Answer: D 🗳️
SHA-1 is the most commonly used SHA algorithm, and produces a 20-byte hash value.
Reference:
https://www.securityinnovationeurope.com/blog/page/whats-the-difference-between-hashing-and-encrypting

What type of attack would be considered a very large flaw in public blockchains such as Bitcoin's Blockchain where the majority of hashpower could possibly be controlled thru an attack?
What is the specific attack Bitcoin could be exposed to?

Correct Answer: A 🗳️
Reference:
https://blockgeeks.com/guides/hypothetical-attacks-on-cryptocurrencies/

How many satoshis are in 1 bitcoin and how many wei in an Ether? (Select two.)

Correct Answer: AB 🗳️
Reference:
http://www.btcsatoshi.com/

In the Proof of Stake(POS) algorithm the miners are really known as ___________?

Correct Answer: C 🗳️
Proof of Stake has the same goal as proof of work""to validate transactions and achieve consensus in the chain""and it uses an algorithm but with a different process. With proof of stake, the creator of a new block "is chosen in a deterministic way, depending on its wealth, also defined as a stake." Since in a proof of stake system, there is no block reward, but the miners, known as forgers, get the transaction fees. Proponents of this shift, including Ethereum co-founder Buterin, like proof of stake for the energy and cost savings realized to get to a distributed form of consensus.
Reference:
http://www.hl.co.uk/news/2018/2/16/a-brief-history-of-blockchain-technology-everyone-should-read

A Byzantine failure is the loss of a system service due to a Byzantine fault in systems that requires________.
What is required?

Correct Answer: A 🗳️
A Byzantine failure is the loss of a system service due to a Byzantine fault in systems that require consensus.
Reference:
https://en.wikipedia.org/wiki/Byzantine_fault_tolerance