Project 2, Part 1 is due Sunday, 22 February.
Quiz 2 will be in class on Wednesday, 25 February. It will be similar in length, format, and content to Quiz 1 (except will cover material from the beginning of the class through
Continue thinking about project ideas!
Mining Harware on the market today: Spondoolies SP20 (this is just an example, certainly not a commercial endorsement!)
Hash rate: 1.7 TH/s
Power use: 1200 W
BTC Price: US$ 240
Difficulty: 44455415962 # from https://blockchain.info/stats, 18 Feb 2015
This spreadsheet has lots of information about bitcoin difficulty over time.
Super Simple Model
>>> expected_hashes / (1.7 * 10**12) 112314445.6981567 # expected seconds to find block >>> _ / (60 * 60 * 24) 1299.935714099036 # days to find block >>> block_value = 240 * 25 >>> earnings_per_year = block_value * (365.25 / 1300) >>> earnings_per_year 1685.769230769231 ```` Why is this estimate of expected earnings totally broken? <div class="gap"> </div> ### Better Model Python code (excerpted below): [mining.py](|filename|./mining-simple.py) ```python def guess_difficulty(month): return difficulty * ((1 + rate_of_difficulty) ** month) hash_rate = 1.7 * 10**12 # 1.7 Th/s hashes_in_month = hash_rate * 60 * 60 * 24 * ave_days_in_month block_value = 25 * 240 # assumes fixed BTC value electricity_cost = (1.2 * kWh) * 24 * ave_days_in_month def expected_revenue(month): success_probability = find_target(guess_difficulty(month)) / 2**256 return block_value * hashes_in_month * success_probability def cumulative_income(months): income = 0.0 for month in range(months): income += expected_revenue(month) - electricity_cost return income
Given this model, when should the miner be turned off and turned to scrap?
What should happen to the bitcoin difficulty when subsidy is halved after block 420,000? (Current block is 344,044 so we should reach block 420,000 in (420000-34400 / (6 * 24)) = 527 days.)
How can an open mining pool fairly determine miners share of the reward? Why is it not sensible to use actual blocks mined to estminate pool share?
What are the risks of a mining pool controlling a large fraction over the hashing power? Does anything dramatic happen when that fraction exceeds 50%?
What Happens At Armageddon? (Ittay Eyal and Emin Gün Sirer, 13 June 2014)