CompSci 461/661

General

Instructor: G. Andrew Stone (gastone@umass.edu): Office Hours on Tues by appointment (send a message on Piazza) or via Zoom (813 149 9032) any day most times (PM me on Piazza). My office is LGRT A246 (Lederle). You can always drop by on Tuesdays even just to chat, but an appointment ensures that I’ll be there!

Syllabus

TAs:
Joseph Majesky jmajesky@umass.edu
Jenish Bajracharya jbajracharya@umass.edu

Graders:
Tasmiya Fathima tfathima@umass.edu
Saumya Pandey saumyapandey@umass.edu

Classroom:
461: Tues 2:30PM - 3:45PM: Computer Sciences Building 140
661: Tues 4:00PM - 5:15PM: Computer Sciences Building 140 (remote students use Zoom meeting: https://umass-amherst.zoom.us/j/92771831987 code 661)

Discussion: Piazza
Assignment Submission: Gradescope Course Entry Code: 8YNPVV
Midterm: In class TBD
Final: BOTH SECTIONS: TBD
For the Midterm and final you may bring a 8.5x11" doublesided HANDWRITTEN by yourself, NOT PRINTED, cheat sheet. If it is too big I will make it smaller by ripping it! If it is not handwritten I will take it before the exam.

General Reference Materials:

Bitcoin (UTXO) blockchain Concepts
Math
Ethereum

In Class Notes and Recordings

Week N notes
Recordings

Weekly Process

Each week we’ll follow the same pattern:

Skim the written materials.
Watch the video, which is an overview of the written material. It does not replace them!
Read through the written materials in detail.
Come to class prepared for discussion with questions remaining from what you read, and ready to answer questions from your instructor. Discussion is not a repeat of the videos. It moves deeper on the video topics, and new material will be introduced! Attendance is mandatory!

Week 2: (Sep 3-9) Cryptography Overview, Doublespend Attacks

We continue our investigation into basic blockchain architecture.

Overview of Applied Cryptography Video Lecture
Doublespend Attack Video Lecture (1/2)
Doublespend Attack (2/2) – note the final equation in this video has some typos although the derivation is correct in essence. Use the equation in Satoshi’s white paper to calculate the likelihood of matching the main chain. And to calculate the probability of exceeding the main chain:

$\lambda = \frac{zq}{p}$
$1- \sum_{k=0}^{z+1} (\frac{\lambda^ke^{-\lambda}}{k!})(1-(q/p)^{z+1-k}), if q < p$

Question to show you really understand the above: Why is lambda zq/p not (z+1)q/p since we stuck z+1 in other places for z?