WEDNESDAY: 3 August 2022. Morning paper. Time Allowed: 2 hours.

This paper has two sections. SECTION I has twenty (20) multiple choice questions. SECTION II has three (3) practical questions of sixty (60) marks. All questions are compulsory. Marks allocated to each question are shown at the end of the question.

1. The following are functions of money. Select the ONE that is NOT
A. Medium of exchange
B. Store of value
C. Standard of deferred payment
D. Unit of currency (2 marks)

2. What is a Blockchain network?
A. A technical infrastructure that provides ledger and smart contract services to applications.
B. A chain of certificate authorities.
C. A technical organisation ethereum services and applications
D. A chain of bitcoin applications (2 marks)

3. The figure below shows a Blockchain network. Select the correct names of the parts labelled (I) and (II) respectively:

A. Previous blocks, hash root
B. Previous blocks, merkle root
C. Previous header, hash root
D. Previous header, merkle root (2 marks)

4. _____ is a separate Blockchain network that connects to another Blockchain
A. Bitcoin
B. Forkchain
C. Sidechain
D. Subchain (2 marks)

5. What is the name given to a set of rules that verify and add transactions to a Blockchain?
A. Blocks
B. Consensus mechanisms
C. Mathematical formulas
D. Laws (2 marks)

6. ___________________ are systems that provide external data sources to smart contracts in Blockchain
A. Routers
B. Fortunes
C. Tokens
D. Oracles (2 marks)

7. Examine the following concepts used to explain the foundation of Blockchain and select the odd ONE out
A. Ledger
B. Ethereum
C. Digital assets
D. Business networks (2 marks)

8. Which of the following stands for the first cryptocurrency with computing power contribution?
A. Gridcoin,
B. Bitcoin,
C. Chaincoin
D. Altcoin (2 marks)

9. Select from the list below an example of Blockchain software available in the market today
A. ICL Blockchain
B. Hyperledger Fabric
C. Hyperledger Rapidev
D. R6 Encoder (2 marks)

10. All of the following are factors to consider when selecting a Blockchain platform EXCEPT one. Which ONE?
A. Scalability Needs
B. The choice of using either new or existing Blockchain platform
C. Security features inherent in the software
D. In-house or standard developed Blockchain (2 marks)

11. In Blockchain networks, there are THREE main kinds of consensus algorithms for arriving at consensus in a distributed manner. Which one is NOT?
A. Proof of Service
B. Proof of Work
C. Proof of Stake
D. Practical Byzantine Fault Tolerance (2 marks)

12. What is the purpose of a mining node in an Ethereum network?
A. To search for necessary information in transactions
B. To implement smart contracts
C. To writing all the transactions that have occurred
D. To search for smart contracts (2 marks)

13. The following are steps in installing solidity program for smart contracts. Which ONE is NOT?
A. Versioning
B. Remix
C. Docker
D. Sectioning (2 marks)

14. Arrange the following basic layout of the source file of Solidity components in the correct order
(I) Import statements to import other contracts/libraries
(II) Add experimental pragma
(III) Choose Solidity version to use
(IV) Contract definition
D. II, I, IV, III (2 marks)

15. What are State Variables as used in solidity?
A. Variables whose values are permanently stored in a contract storage
B. Variables whose values are present till function is executed.
C. Special variables existing in the global namespace used to get information about the Blockchain
D. Variables whose values are temporarily stored in a contract storage (2 marks)

16. Select a reserved Solidity keyword from the list below
A. Checked
B. Locatable
C. Catch
D. Try (2 marks)

17. Blockchain is a peer-to-peer _____________ distributed ledger technology that makes the records of any digital asset transparent and unchangeable.
A. Decentralised
B. Locally
C. Secure
D. Highly (2 marks)

18. Select the sentence that correctly completes the following statement: Blockchain can perform user transactions __________
A. With the help of the third party
B. Without involving any third party
C. Without involving anyone
D. Without involving any authentication (2 marks)

19. What does a block in a Blockchain contain?
A. Header and Digital ledger
B. Bitcoins and Input
C. Transactions and Bitcoins
D. Header and Transaction (2 marks)

20. Which of the following hosts the software needed for transaction initiation, validation, mining, block creation, and smart contract execution?
A. User Account
B. Solidity
C. Ethereum full node
D. Smart Contract (2 marks)


21.  Explain how a safe remote purchase smart contract is executed using the steps shown in the diagram below

Outline three variables and four functions that can be used in implementing the purchase smart contract above. (7 marks)

22.  Create a smart contract named MyContract having a state variable as owner. Create a constructor to fetch the address of the owner from msg and hold it into the state variable owner. Also, create a function get Balance () to show the current balance of the owner. (8 marks)

In block chain a block is an object that has some information on it. Write a code to create a Block class. (4 marks)

In reference to the block created above, implement a hashing function using SHA256 algorithm with the Nodejs’ built-in crypto package. (8 marks)

23. Study the Blockchain voting system shown in the figure below and explain clearly how the process works.

Give five advantages of using such a system over manual voting system. (5 marks)

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