1) The midterm discussion covered confirmations in cryptocurrency transactions and the average wait time for the first confirmation. 2) It was noted that the threshold for being considered a "bitcoin expert" based on answering questions well on the midterm was around 85% of questions answered correctly. 3) Students were given updates on assignment due dates and opportunities to improve their midterm score by identifying and correcting incorrect statements in a referenced blockchain report.

1. Class 18:
Midterm
Confirmations
Cryptocurrency Cabal
cs4501 Fall 2015
David Evans and Samee Zahur
University of Virginia

2. Plan for Today
Midterm Discussion
1
Schedule Update:
PS3 is due Sunday, November 8
(There is no PS4)
Project Pre-Proposal: Friday, November 13
Project Update: Monday, November 23
Last class: Monday, December 7

3. 12
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Midterm Summary
2
Numberansweringwell(outof30)
Threshold of
“bitcoin expert”
qualification ~ 85

4. Confirmations
3

5. How long is the expected wait for
the first confirmation?
4

6. 5

7. Poisson Process
6
Bitcoin mining is memoryless:

8. 7

9. 8
Blockchain.info

10. 9

11. 10
https://www.quandl.com/data/BCHAIN/ATRCT-Bitcoin-Average-Transaction-Confirmation-Time
Project idea?
How can average transaction confirmation time be less than Poisson rate?

12. Can we gain confidence without
confirmations?
11

13. 12

14. “Pre-confirmations”?
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15. 14

16. 15
How do buyer and seller interact in a bitcoin transaction?

17. “Third-party intermediary”
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18. 17

19. 18

20. 19

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18 18 18
27
26
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9
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Numberansweringwell(outof30)
Threshold of
“bitcoin expert”
qualification ~ 85

22. 12
18 18 18
27
26
23
22
9
7
10
4
1 2 3 4 5 6 7 8 9 10 11 12
21
Numberansweringwell(outof30)
Threshold of
“bitcoin expert”
qualification ~ 85
If you didn’t reach “expert” qualification
on the Midterm because of poor answer
to questions 1-4, you can improve your
score by finding incorrect statements in
the Blockchain Report Josh mentioned,
and restating them correctly (and clearly).

23. Transaction Scripts
22

24. Transaction Scripts
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25. Charge
Upcoming office hours:
Now: 3:30-4:30pm (Samee, Rice 442)
Tomorrow: 2:30-3:30pm (Dave, Rice 507)
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