Question 1: Among the Ethereum addresses, public keys, and private keys, which statement is TRUE?

• The address serves as the public key; both are 20 bytes long, whereas the private key is 32 bytes long.
• An address is 20 bytes long, a public key is 64 bytes and the private key is 32 bytes (Correct answer)
• A public key is 32 characters, a private key is 64 characters long, and an address is 20 characters long.

Correct answer: An address is 20 bytes long, a public key is 64 bytes and the private key is 32 bytes

In Ethereum's cryptographic architecture, a private key is a 32-byte (256-bit) random number. From this private key, a 64-byte (512-bit) public key is derived using elliptic curve cryptography. Finally, an Ethereum address is generated by taking the last 20 bytes of the Keccak-256 hash of the public key.

Question 2: In solidity, the outcome of dividing number -5 by integer 2 is

• -2.5 as a result of the automated casting or conversion into a float.
• Since Solidity only understands unsigned integers, it is not possible.
• -2 due to the truncated decimal (rounded to zero) (Correct answer)
• -3 as it is always rounded.

Correct answer: -2 due to the truncated decimal (rounded to zero)

In Solidity, integer division truncates any decimal part, effectively rounding the result towards zero. Therefore, when dividing -5 by 2, the mathematical result is -2.5, but Solidity's integer division truncates this to -2. This behavior is standard for integer arithmetic in many programming languages.

Question 3: What does it mean when we say, "A Hashing Algorithm is deterministic"?

• Given a lengthy input, it produces the result using equally scattered data.
• Given the output, it shouldn't be feasible to generate the input again.
• When given the same input, it always generates the same output. (Correct answer)

Correct answer: When given the same input, it always generates the same output.

A deterministic hashing algorithm is one that consistently produces the exact same output hash whenever it is given the identical input. This property is fundamental to blockchain technology, as it ensures that data integrity can be reliably verified and that all network participants can independently and consistently arrive at the same hash for a given piece of data.

Question 4: What functions do private keys represent?

• To create a transaction-capable address.
• To serve as a cryptographically significant shield for the Public Keys.
• To verify signatures on documents and determine an address from. (Correct answer)

Correct answer: To verify signatures on documents and determine an address from.

Private keys serve critical functions in Ethereum's security model. They are used to cryptographically sign transactions, proving ownership of an address and authorizing fund transfers or contract interactions without revealing the private key itself. Additionally, an Ethereum address is deterministically derived from its corresponding public key, which in turn is generated from the private key.

Question 5: What does a transaction's nonce-field imply?

• Adding a second checksum to transactions
• All ethers sent from that address combined
• To defend off replay attacks (Correct answer)

Correct answer: To defend off replay attacks

The `nonce` field in an Ethereum transaction is a sequential counter that tracks the number of transactions sent from a specific address. Its primary purpose is to prevent 'replay attacks,' where a malicious actor might attempt to re-broadcast an old, valid transaction. By requiring each transaction to have a unique, incrementing nonce, the network ensures that every transaction is processed only once.

Question 6: Complete the statement, "DApps are..".

• For banks and other large financial institutions, a novel application of logical processes. In this way, they may operate with less people and higher security.
• Good, that they eliminate the middleman, operate on a reliable platform, add logic to the blockchain where existing financial assets are already functioning, and so enable peer-to-peer trade.
• A great method for developing new applications. These platforms' apps run totally independently of one another and support logical interactions. They are unable to access any money, which adds another element of trust.

Correct answer is missing, so an explanation cannot be provided.

Question 7: Choose the correct scientific notation?

• 1 Ether = 10^18 wei, 10^6 Gwei, 10^6 Finney
• 1 Ether = 10^18 wei, 10^9 Gwei, 10^3 Finney (Correct answer)
• 1 Ether = 10^16 wei, 10^13 Gwei, 10^3 Finney
• 1 Ether = 10^19 wei, 10^13 Gwei, 10^3 Finney

Correct answer: 1 Ether = 10^18 wei, 10^9 Gwei, 10^3 Finney

Ethereum uses various denominations for its native currency, Ether, to represent different values. The smallest unit is `wei`, with 1 Ether being equivalent to 10^18 wei. Other common units include `Gwei` (giga-wei), where 1 Ether equals 10^9 Gwei, and `Finney`, where 1 Ether equals 10^3 Finney, providing convenient ways to express transaction amounts.

Question 8: It is best to use the blockchain to its full potential...

• To only utilize it for purposes that require the advantages of the blockchain. (Correct answer)
• To apply it to the entire business logic. Having everything in one location is always preferable.
• Both statements are correct.

Correct answer: To only utilize it for purposes that require the advantages of the blockchain.

To leverage the blockchain effectively, it's crucial to use it judiciously, only for purposes that genuinely benefit from its unique advantages like decentralization, immutability, and censorship resistance. Overloading the blockchain with non-essential business logic can lead to increased complexity, higher gas costs, and reduced performance. A focused approach ensures efficiency, maintainability, and optimal resource utilization.

Question 9: Which statement is TRUE about Proof of Work (PoW) and Proof of Stake.

• PoS mining uses specialized brand-new hardware that must be acquired with a network-wide stack of ether. Thus the name, which comes from Stack and is called Proof of Stake.
• PoW has a high energy requirement due to its computational complexity. But at the other hand, mining a block and adding transactions results in a clear reward for the miner. (Correct answer)
• PoW is superior to PoS since the network uses more energy when PoS is used.

Correct answer: PoW has a high energy requirement due to its computational complexity. But at the other hand, mining a block and adding transactions results in a clear reward for the miner.

Proof of Work (PoW) consensus mechanisms, like those historically used by Ethereum, require significant computational power, leading to high energy consumption. Despite this, PoW offers a clear incentive structure: miners who successfully solve the cryptographic puzzle and add a new block to the blockchain receive a reward, typically consisting of newly minted cryptocurrency and transaction fees. This reward motivates miners to secure the network.

Question 10: How many stakeholders made up the DAO?

• 10000
• 18000 (Correct answer)
• 35000
• 48000

Correct answer: 18000

The DAO was a decentralized autonomous organization launched on the Ethereum blockchain that raised a significant amount of Ether through a crowdfunding campaign. Historical data indicates that approximately 18,000 unique addresses contributed to the DAO, making them its stakeholders. This large number of participants highlighted the early interest in decentralized governance.

Question 11: What programming language was used to create the Trinity eth2 client?

• Python (Correct answer)
• C++
• Cobol
• Rust

Correct answer: Python

Trinity was one of the early client implementations for Ethereum 2.0 (now known as the Consensus Layer). It was developed by the Ethereum Foundation and notably written in the Python programming language. While other Ethereum clients utilize different languages like Go, Rust, or C++, Trinity distinguished itself with its Python codebase.