How software works : the magic behind encryption, CGI, search engines, and other everyday technologies

224 Pages·2015·7.38 MB·English

by  V. Anton

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HOW SOFTWARE WORKS
The Magic Behind Encryption, CGI, Search Engines, and
Other Everyday Technologies
by V. Anton Spraul
San Francisco
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HOW SOFTWARE WORKS. Copyright © 2015 by V. Anton Spraul.
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior
written permission of the copyright owner and the publisher.
Printed in USA
First printing
19 18 17 16 15 1 2 3 4 5 6 7 8 9
ISBN-10: 1-59327-666-4
ISBN-13: 978-1-59327-666-9
Publisher: William Pollock
Production Editor: Alison Law
Cover Illustration: Josh Ellingson
Interior Design: Octopod Studios
Developmental Editors: Hayley Baker, Seph Kramer, and Greg Poulos
Technical Reviewer: Randall Hyde
Copyeditor: Rachel Monaghan
Compositor: Susan Glinert Stevens
Proofreader: James Fraleigh
For information on distribution, translations, or bulk sales, please contact No Starch Press, Inc. directly:
No Starch Press, Inc.
245 8th Street, San Francisco, CA 94103
phone: [phone]; [e-mail]
www.nostarch.com
Library of Congress Cataloging-in-Publication Data:
Spraul, V. Anton.
How software works : the magic behind encryption, CGI, search engines, and other everyday technologies / by
V. Anton Spraul.
pages cm
Includes index.
Summary: “A guide for non-technical readers that explores topics like data encryption; computer graphics
creation; password protection; video compression; how data is found in huge databases; how programs can work
together on the same problem without conflict; and how map software finds routes.”— Provided by publisher.
ISBN 978-1-59327-666-9 — ISBN 1-59327-666-4
1. Electronic data processing—Popular works. 2. Computer software—Popular works. 3. Computer networks—
Popular works. I. Title.
QA76.5.S6663 2015
005.3—dc23
2015022623
No Starch Press and the No Starch Press logo are registered trademarks of No Starch Press, Inc. Other product and
company names mentioned herein may be the trademarks of their respective owners. Rather than use a trademark
symbol with every occurrence of a trademarked name, we are using the names only in an editorial fashion and to the
benefit of the trademark owner, with no intention of infringement of the trademark.
The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has been taken
in the preparation of this work, neither the author nor No Starch Press, Inc. shall have any liability to any person or
entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information
contained in it.
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About the Author
V. Anton Spraul has taught introductory programming and computer science to students
from all over the world for more than 15 years. He is also the author of Think Like a
Programmer (No Starch Press) and Computer Science Made Simple (Broadway).
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About the Technical Reviewer
Randall Hyde is the author of The Art of Assembly Language and Write Great Code (both
No Starch Press), and is also the co-author of The Waite Group’s Microsoft Macro
Assembler 6.0 Bible (Sams Publishing). Hyde taught assembly language at the University
of California, Riverside, for more than a decade and has been programming software for
nuclear reactor consoles for the past 12 years.
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Brief Contents
Acknowledgments
Introduction
Chapter 1: Encryption
Chapter 2: Passwords
Chapter 3: Web Security
Chapter 4: Movie CGI
Chapter 5: Game Graphics
Chapter 6: Data Compression
Chapter 7: Search
Chapter 8: Concurrency
Chapter 9: Map Routes
Index
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Contents in Detail
Acknowledgments
Introduction
Who This Book Is For
Topics Covered
Behind the Magic
1 Encryption
The Goal of Encryption
Transposition: Same Data, Different Order
Cipher Keys
Attacking the Encryption
Substitution: Replacing Data
Varying the Substitution Pattern
Key Expansion
The Advanced Encryption Standard
Binary Basics
AES Encryption: The Big Picture
Key Expansion in AES
AES Encryption Rounds
Block Chaining
Why AES Is Secure
Possible AES Attacks
The Limits of Private-Key Encryption
2 Passwords
Transforming a Password into a Number
Properties of Good Hash Functions
The MD5 Hash Function
Encoding the Password
Bitwise Operations
MD5 Hashing Rounds
Meeting the Criteria of a Good Hash Function
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Digital Signatures
The Problem of Identity
Collision Attacks
Passwords in Authentication Systems
The Dangers of Password Tables
Hashing Passwords
Dictionary Attacks
Hash Tables
Hash Chaining
Iterative Hashing
Salting Passwords
Are Password Tables Safe?
Password Storage Services
A Final Thought
3 Web Security
How Public-Key Cryptography Solves the Shared Key Problem
Math Tools for Public-Key Cryptography
Invertible Functions
One-Way Functions
Trapdoor Functions
The RSA Encryption Method
Creating the Keys
Encrypting Data with RSA
RSA Effectiveness
RSA Use in the Real World
RSA for Authentication
Security on the Web: HTTPS
Handshaking
Transmitting Data Under HTTPS
The Shared Key Problem Solved?
4 Movie CGI
Software for Traditional Animation
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How Digital Images Work
How Colors Are Defined
How Software Makes Cel Animations
From Cel Animation Software to Rendered 2D Graphics
Software for 3D CGI
How 3D Scenes Are Described
The Virtual Camera
Direct Lighting
Global Illumination
How Light Is Traced
Full-Scene Anti-Aliasing
Combining the Real and the Fake
The Ideal of Movie-Quality Rendering
5 Game Graphics
Hardware for Real-Time Graphics
Why Games Don’t Ray Trace
All Lines and No Curves
Projection Without Ray Tracing
Rendering Triangles
The Painter’s Algorithm
Depth Buffering
Real-Time Lighting
Shadows
Ambient Light and Ambient Occlusion
Texture Mapping
Nearest-Neighbor Sampling
Bilinear Filtering
Mipmaps
Trilinear Filtering
Reflections
Faking Curves
Distant Impostors
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Bump Mapping
Tessellation
Anti-Aliasing in Real Time
Supersampling
Multisampling
Post-Process Anti-Aliasing
The Rendering Budget
What’s Next for Game Graphics
6 Data Compression
Run-Length Encoding
Dictionary Compression
The Basic Method
Huffman Encoding
Reorganizing Data for Better Compression
Predictive Encoding
Quantization
JPEG Images
A Different Way to Store Colors
The Discrete Cosine Transform
The DCT for Two Dimensions
Compressing the Results
JPEG Picture Quality
Compressing High-Definition Video
Temporal Redundancy
MPEG-2 Video Compression
Video Quality with Temporal Compression
The Present and Future of Video Compression
7 Search
Defining the Search Problem
Putting Data in Order
Selection Sort
Quicksort
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