Public Keys, One Way Functions and Hard Problems

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Lesson synopsis

Public KeySecurity has always been a major focus of computer science research, and with the explosion of Internet use by commerce, the need for secure transactions has taken on more urgency. Most recently, cyber-thieves demonstrated that true security on the Internet is going to require a new level of understanding of how to protect personal data, and more importantly, financial transactions. This lesson introduces two important concepts: public key encryption and one-way functions. It provides an opportunity for students to understand the underpinnings of almost all Internet security: they will come to appreciate that any lock can be eventually broken, and that theoretical computer scientists study ‘hard’ problems to lengthen the time it will take to break a lock. Note that this is not a lesson in encryption, but in how mathematics is used to secure information.

Age Levels

11 - 14 years

Objectives

Introduce students to:
The concept of a public key
How the modulo function is a one-way function
How the Diffie-Hellman key exchange uses a one-way function
What computer scientists mean by ‘hard’ problems

Anticipated learner outcomes

Students will be able to
Practice creating public keys with the classic color model.
Exchange information with the Diffie-Hellman method using modulo arithmetic.
Explain why no lock can be completely secured, and that given time, any mathematical ‘lock’ can be broken.
Use exponentiation and modulo arithmetic to create cyber-keys.
@ symbol
Ray Tomlinson
Ray Tomlinson

Have you ever considered that someone, at some point, was in a position to choose what symbol would be used separate the user from their location in an email address? That person, it turns out, was Ray Tomlinson, and in 1971 he chose "@". Tomlinson is credited with demonstrating the first email sent between computers on a network, and when asked what inspired him to make this selection he said, “Mostly because it seemed like a neat idea.”

After completing his Master’s degree at MIT in 1965, Ray joined the Information Sciences Division of Bolt Beranek and Newman Inc. of Cambridge, Massachusetts. Since then he has made many notable contributions to the world of network computing. He was a co-developer of the TENEX computer system that was popular in the earliest days of the Internet; he developed the packet radio protocols used in the earliest internetworking experiments; he created the first implementation of TCP; and he was the principle designer of the first workstation attached to the Internet.

Liz Gerber - Image credit Lisa Beth Anderson
Liz Gerber
Liz Gerber - Image credit Lisa Beth Anderson

Liz Gerber earned her MS and PhD in Product Design and Management Science and Engineering at Stanford. She specializes in design and human-computer interaction, particularly how social computing supports the innovation process. Her current research investigates crowd-funding as a mechanism for reducing disparities in entrepreneurship.
Gerber's work funded by the US National Science Foundation and the National Collegiate Inventors and Innovators Alliance has appeared in peer-reviewed journals, including Transactions on Computer Human Interactions, Design Studies, and Organization Science.
As an award-winning teacher and researcher, Liz has touched the lives of more than 6,000 students through her teaching at Northwestern's Segal Design Institute and Stanford University's Hasso Plattner's Institute of Design and through her paradigm-shifting creation, Design for America, a national network of students using design to tackle social challenges.

Image credit - Lisa Beth Anderson

King's Quest
Roberta Williams

Video games immerse users in a world of high tech thrills, stunning visuals, unique challenges, and interactivity. They enable users to become a warrior princess or a gruesome ghoul, create a virtual persona, or even develop worlds that other gamers can play on. But before the games of today became reality, they were the dreams of a few innovative individuals.

Roberta Williams is considered one of the pioneers of gaming as we know it today. During the 80’s and 90’s along with husband Ken Williams through their company On-Line Systems, she developed some of the first graphical adventure games. These included such titles as Mystery House, Wizard and the Princess and the popular King’s Quest series. Williams also helped introduce more girls and women to the world of gaming by bringing games developed from a woman’s perspective to mainstream market.

Gordon and SenseCam QUT
Gordon Bell
Gordon and SenseCam QUT

Gordon Bell is a pioneering computer designer with an influential career in industry, academia and government. He graduated from MIT with a degree in electrical engineering. From 1960, at Digital Equipment Corporation (DEC), he designed the first mini- and time-sharing computers and was responsible for DEC's VAX as Vice President of R&D, with a 6 year sabbatical at Carnegie Mellon University. In 1987, as NSF’s first, Ass't Director for Computing (CISE), he led the National Research Network panel that became the Internet. Bell maintains three interests: computing, lifelogging, and startup companies—advising over 100 companies. He is a Fellow of the, Association of Computing Machinery, Institute of Electrical and Electronic Engineers, and four academies. He received The 1991 National Medal of Technology. He is a founding trustee of the Computer History Museum, Mountain View, CA. and is an Researcher Emeritus at Microsoft. His 3 word descriptor: Computing my life; computing, my life.

Turing machine
Alan Mathison Turing
Alan Mathison Turing

Did you know that computing has been used in military espionage and has even influenced the outcome of major wars? Alan Mathison Turing designed the code breaking machine that enabled the deciphering of German communications during WWII. As per the words of Winston Churchill, this would remain the single largest contribution to victory. In addition, he laid the groundwork for visionary fields such as automatic computing engines, artificial intelligence and morphogenesis. Despite his influential work in the field of computing, Turing experienced extreme prejudice during his lifetime regarding his sexual orientation. There is no doubt that computers are ubiquitously part of our lives due to the infusion of Turing’s contributions.

Image credits