Pub. Date:
Algonquin Books of Chapel Hill
In Code: A Mathematical Journey

In Code: A Mathematical Journey

by David Flannery, Sarah Flannery


View All Available Formats & Editions
Current price is , Original price is $24.95. You
Select a Purchase Option (Reprint)
  • purchase options
    $19.33 $24.95 Save 23% Current price is $19.33, Original price is $24.95. You Save 23%.
  • purchase options
    $10.62 $24.95 Save 57% Current price is $10.62, Original price is $24.95. You Save 57%.
    Note: Access code and/or supplemental material are not guaranteed to be included with textbook rental or used textbook.
  • purchase options

Product Details

ISBN-13: 9781565123779
Publisher: Algonquin Books of Chapel Hill
Publication date: 12/30/2002
Edition description: Reprint
Pages: 362
Sales rank: 841,707
Product dimensions: 6.00(w) x 9.00(h) x 0.81(d)

About the Author

David Flannery lectures on mathematics at Ireland's Cork Institute of Technology

Read an Excerpt

4 Dad's Evening Class

God made the natural numbers, all the rest is the work of Man.

-leopold kronecker

These were the first words that my father wrote on the board-a bit alarmingly, in German-on the evening of my first class at the Cork Institute of Technology, where he lectures in mathematics. He explained that Kronecker was a German mathematician who lived in the nineteenth century. Little did I know the role that the natural numbers (1, 2, 3, and so on . . .) would play in my life over the next two years.

Although, as I have already said, my father had often taught or helped with my school mathematics at home, this was the first time I had ever attended a formal lecture of his and seen him present work in an organized way to a group of people. This unusual evening class had come about as a result of a conversation he and I had the previous summer, which started something like, "Now that you have decided to do transition year, I must do some math with you." He continued, "I'd like to show you how some beautiful but reasonably elementary mathematics is applied, stuff that you wouldn't ordinarily come across in school."

Not knowing exactly what he had in mind, but not wishing to be collared and dragged to the kitchen blackboard at random times, I replied, "Dad, whatever you do, do something structured!" He promised to think carefully about the most effective but gentle way to give me a realistic glimpse into the mathematical world. Conscious of how much he would have appreciated it had someone done this for him thirty years ago, he felt obliged now to offer me the benefit of his

mathematical knowledge. "Of course, only if you are genuinely interested-I wouldn't force it on you."

Of course he wouldn't! But I was interested. So this is how the evening class was conceived, and this is how I was to be introduced to many wonderful mathematical ideas-accessible ideas I might never otherwise have encountered unless I chose to pursue mathematics as a career.

The title for the intended series of lectures, "Mathematical Excursions," was suggested by one of Dad's favorite books, Excursions in Calculus by Robert M. Young. Dad wanted not to present mathematics in a very rigorous fashion, but rather to explore "elementary" aspects of "higher" mathematics, and learn how these ideas find applications in different fields of study outside mathematics. The only prerequisite for these excursions-besides a thorough grounding in ordinary arithmetic and basic algebra-was interest. The primary aim of the course was that everybody take pleasure in sharing in the spirit of discovery.

The class, which met Tuesday evenings from seven to ten, consisted of eight people and ran for twenty-five nights. At fifteen and a half I was the youngest, though there were a couple others nearly as young. The rest were adults of various backgrounds: one was a secondary school mathematics teacher, one a chemistry graduate working in a medical laboratory, and others were computer scientists. All were there either because they had loved math at school but hadn't continued with it, or because they felt they hadn't properly appreciated the subject the first time around. This noncredit class, which was not part of any major, led to no award or certification at its completion and demanded no homework or study, may have seemed an ideal way of "getting back into math" in an easygoing, informal manner. Dad told us at the outset that there would be no pressure to perform, and that we need not fear being asked questions but we could ask them at any time. We were to feel free to say "any crazy thing" we liked, and not to be in the least afraid of appearing to make fools of ourselves. In fact, he told us, the more you are prepared to make a fool of yourself the more you'll learn. These reassurances convinced me that I was going to enjoy the next few Tuesday nights, even if I was not completely comfortable with the fact that the lecturer was my father. (Students always pity those who have to endure classes given by their parents, though I'm sure the situation is worse for the parent who is the teacher.)

The first excursions were to be in elementary number theory, with some aspects of cryptography as their final destination. Along the way we would see interesting sights, rich in their own right regardless of whether or not they had immediate application. Dad told us that when he was a student, number theory was regarded as the sole province of mathematicians, and those who devoted their lives to its study were considered the purest of the pure, so few were its perceived applications. It wasn't until the 1960s that engineers and scientists began to find applications of number theory, and by the end of the 1970s the discipline came of age, in the applied sense, with the advent of public key cryptography (very briefly, a modern form of cryptography which makes it possible to make public the method by which messages are enciphered, but-amazingly-without revealing how these enciphered messages are deciphered). Now the U.S. government was putting millions of dollars into the study of cryptography, a subject full of wonderful ideas about which, Dad said, he could hardly wait to tell us. Whereas many great number theorists had barely made a living in the past, their modern counterparts were now being actively sought out, so great was the demand for expertise in this emerging science of secrecy which relied so fundamentally on the branch of mathematics that the great mathematician Karl Friedrich Gauss (of whom more later) revered above

all else. It was he who said:

Mathematics is the queen of the sciences and number theory is the queen of mathematics.

As you might imagine, hearing all this filled me with curiosity and interest. Mom said it was like the Sleeping Beauty fairy tale, and she was prompted to write:

A princess was the Theory of Number,

whom no practical use did encumber,

'til Cryptography the prince

('tis all secrecy since),

did kiss her awake from her slumber.

I thought about those who had toiled away through the centuries at unraveling the mysteries of this subject, motivated by nothing more than a passionate desire to know. They could have hardly dreamt of the applications that some of their results would one day find. I wondered what it was they had discovered, and what they would think if they could see how some of these discoveries are now being used. I was eager to learn the subject and surmise for myself whether they would be surprised or not.

We were at once tantalized and put on our guard by the warning that number theory is notoriously deceptive. We were told that very soon we'd find ourselves asking simple questions, many of which others have asked before us through the ages, and some of which have still not been answered to this day.

Table of Contents

Part IBackground1
1Early Influences3
2Early Challenges8
3Beginning My First Project32
Part IIMathematical Excursions41
4Dad's Evening Class43
5Of Prime Importance47
6The Arithmetic of Cryptography71
7Sums with a Difference113
8One Way Only149
9Public Key Cryptography164
Part IIIExhibition Time187
10Young Scientist '98189
11The Birth of a Project194
12Young Scientist '99218
Part IVAfter-Math229
13Media Blitz231
14Around the World and Back254
About This Book269
Appendix A"Cryptography--A New Algorithm Versus the RSA"271
Appendix BAnswers to Miscellaneous Questions297
Appendix CEuclid's Algorithm305
Appendix DThe Euler [phis]-function and the Euler-Fermat Theorem315


Exclusive Author Essay
I would never have thought that by the end of my first year at university I'd be sitting at a computer in a beautiful room in Peterhouse, Cambridge, composing a short piece about how the fates made me an [unwilling] author a little over a year ago while I was still at school.

One horrible memory of my secondary education is that almost every other weekend was marred by the awful feeling that comes of knowing that an essay is due first thing on Monday morning. These essays used to take 'forever'! Having inherited some of my father's perfectionist qualities I would take simply ages just to get going. Before even considering putting pen to paper I'd look up relevant material, search through old newspapers and wade through my treasured book of quotations. However much I promised myself that I would settle down to work in plenty of time, I could never do so until the very last minute which was usually about 9 or 10 o'clock on Sunday night. Then the essay, good or bad, would just have to stream out onto the previously terrifying blank pages.

Afterwards, I'd chastise myself for managing to ruin yet another weekend by leaving the dreaded essay to hang over me rather than getting it out of the way as soon as possible. In truth, curiously, I loved these essays and relished the challenge they presented. Imagine then how I felt when Dad and I were invited to write In Code. The invitation came at the epicenter of an explosion of publicity which engulfed me after winning the Irish Young Scientist competition and while I was still in my final year at school. Do an extra essay outside of school just for "the fun and the experience." No thank you! Initially I dismissed the possibility completely, but Dad thought we should think it over. We thought about the offer for months. Eventually we decided that the challenge and the opportunity were too great to be passed up.

So for a few days before I went to visit my pen friend in Paris I sat down to see what I could do. I think I wrote solidly for days. I decided to start with what I thought would be a relatively easy task: describing my experiences on those days immediately before, and after, winning the Young Scientist award. I read through my diary entries from the time and looked at the rather amazing collection of newspaper clippings I had gathered. All the emotions I had at the time were made fresh in my mind. As I wrote I can remember my stomach being gripped by that same butterfly-filled feeling that I had throughout the competition. I included some very personal feelings in what I wrote, as well as explaining the sheer excitement of being judged and quizzed on a project which I had so thoroughly enjoyed doing. Once I had poured out all these feelings about what was really a large part of my life up to then, I decided I couldn't turn back.

I can assure you that all the tortures of my essay experiences paled into insignificance in comparison to the work that I did with my wonderful father while writing this book. But it was worth every minute! I hope that what we have written in In Code will help you understand that math and science projects can be truly very exciting. Thankfully, math involves wonderfully little in the way of writing essays! (Sarah Flannery)

Customer Reviews

Most Helpful Customer Reviews

See All Customer Reviews

In Code: A Mathematical Journey 4 out of 5 based on 0 ratings. 1 reviews.
uawelder on LibraryThing 19 days ago
I found this book to be both enjoyable and educational. I learned about some interesting existing encryption methods, the math that supports them, and ultimately how they might be compromised. She has done an excellent job and i certainly hope this is more than just a 15sec of fame for her.