2022/5/20 14:03 ECS796P Exam (page 4 of 4)
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EECS SUMMER EXAMINATION PERIOD SUBMISSION PAGE 2021/22
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QUESTION12 5.00
Decide if the following sentences about Proof of Work in the Bitcoin cryptocurrency are True or False:
1. Mining difficulty for Proof of Work has increased over time:
2. Every 2016 blocks the mining difficult doubles:
3. As of January 2022 the difficulty target for the Bitcoin cryptocurrency is in the order of billions:
4. The Bitcoin Proof of Work algorithm consumes more energy than the UK:
5. A block is accepted by the network if the hash of the block and the nonce is lower than the difficulty targer:
True False
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2/5/20 14:03 ECS796P Exam (page 4 of 4)
QUESTION13 10.00
Consider a thresholding scheme and reputation scheme for preventing stake grinding in the proof of stake algorithm. Complete the sentences, selecting the right match.
The thresholding scheme function as follows:
Each validator will record the number of transactions it processes in a time period. If this number reaches a threshold then the validator
After a certain time period has passed the
The reputation scheme function as follows:
Each validator has a reputation value which is initialised at zero.
If a validator processes more than a certain number of blocks in a time period the reputation value is
If a validator processes less than a certain number of blocks in a time period the reputation value is
The section algorithm uses the reputation value when selecting the next validator to make validators with
reputation values less likely to be selected and validators with reputation values more likely to be selected.
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2/5/20 14:03 ECS796P Exam (page 4 of 4)
QUESTION14 10.00
Here you see the circuit diagram for the SHA256 algorithm. Drag and drop the mathematical description to the correct circuit. Note variable names have been changed to generic x, y, z values.
(x rightrotate 6) xor (x rightrotate 11) xor (x rightrotate 25)
(x rightrotate 2) xor (x rightrotate 13) xor (x rightrotate 22)
(x and y) xor (x and z) xor (y and z)
(x and y) xor ((not x) and z)
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