Bonus
Torben Pedersen lends his name to an “information-theoretically hiding” one of these protocols. For 10 points each:
[10h] Name these two-step protocols that consist of a namesake initial phase followed by a “reveal” phase. These binding cryptographic primitives allow one party to select a value that cannot be changed after it is selected.
ANSWER: commitment schemes [accept bit commitment schemes; accept Pedersen commitment scheme or information-theoretically hiding commitment scheme or commit phase; prompt on schemes]
[10e] Manuel Blum’s seminal paper on commitment schemes is titled for performing this action “by telephone.” Performing this physical action once is the prototypical example of a Bernoulli trial.
ANSWER: coin flipping [accept descriptions such as flipping a coin or winning a coin toss or playing heads or tails; accept “Coin Flipping by Telephone”]
[10m] Blum’s procedure for coin flipping by telephone is based on one of these functions. Due to their pre-image resistance, hash functions are often considered these functions, which are easy to compute but difficult to invert.
ANSWER: one-way functions [or OWFs; accept trapdoor functions or trapdoor one-way functions]
<Other Science>
Answerlines and category may not exactly match the version played at all sites
Conversion
| Team | Opponent | Part 1 | Part 2 | Part 3 | Total | Parts |
|---|---|---|---|---|---|---|
| Arizona State | UC Berkeley B | 0 | 10 | 10 | 20 | EM |
| British Columbia | LSE | 0 | 10 | 10 | 20 | EM |
| Chicago A | Rutgers | 0 | 10 | 10 | 20 | EM |
| Chicago B | Minnesota | 0 | 10 | 0 | 10 | E |
| Cornell A | Texas | 0 | 10 | 10 | 20 | EM |
| Florida | NYU | 0 | 10 | 0 | 10 | E |
| Georgia Tech | Johns Hopkins | 0 | 0 | 10 | 10 | M |
| Illinois B | RIT | 0 | 10 | 10 | 20 | EM |
| Indiana | Illinois A | 0 | 10 | 10 | 20 | EM |
| MIT | Toronto C | 10 | 10 | 10 | 30 | HEM |
| Maryland | Columbia B | 0 | 10 | 10 | 20 | EM |
| North Carolina A | Columbia A | 0 | 10 | 10 | 20 | EM |
| Ohio State | North Carolina B | 0 | 0 | 0 | 0 | |
| Penn State | WUSTL B | 0 | 10 | 0 | 10 | E |
| Stanford | Toronto A | 0 | 10 | 10 | 20 | EM |
| Toronto B | Harvard | 0 | 10 | 10 | 20 | EM |
| UCF | Cornell B | 0 | 10 | 10 | 20 | EM |
| Virginia | Michigan | 0 | 10 | 0 | 10 | E |
| Virginia Tech | Iowa State | 0 | 0 | 10 | 10 | M |
| WUSTL A | Northwestern | 0 | 10 | 0 | 10 | E |
| Waterloo A | UC Berkeley A | 0 | 10 | 10 | 20 | EM |
| Waterloo B | Ottawa | 10 | 10 | 10 | 30 | HEM |
| Winona State | Vanderbilt | 0 | 10 | 10 | 20 | EM |
Summary
| Tournament | Exact Match? | Heard | PPB | Easy % | Medium % | Hard % |
|---|---|---|---|---|---|---|
| 2025 ACF Nationals | Yes | 23 | 16.96 | 87% | 74% | 9% |