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About this Article
Written by: Patrick Vanderwall
Written on: December 4th, 2016
Tags: computer science, computer engineering, cryptography, lifestyle, digital security
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About the Author
Patrick Vanderwall was a student at USC when this article was written.
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Volume XVIII Issue II > Cryptography and Communication Security in a Digital Age
Have you ever forgotten your password on a website where you made an account months before? The process of retrieving that password begins with a trial and error process of running through your familiar passwords and usually ends with a frustrated click on the “Forgot password?” button nearby. After refreshing your inbox in search of an email the website sent you, the instructions on how to access your account finally arrive. Here’s the red flag: that email contains your old password in plain text. If you find yourself in this position, you are forced to question the security of that website and consider erasing your account.

Introduction

Internet security is becoming an increasingly important concern in this digital age, especially as we find ourselves storing an exponential amount of personal and private information online. Here’s a helpful hint: never store your passwords in plain text. Doing so increases the potential risk of security breaches to online databases and, perhaps more importantly, your own account information. If a hacker were to break into a password database filled with plain-text passwords, they would have immediate access to a number of accounts. This is where the importance of cryptography, or more specifically, encryption, comes into play for the creation of secure data systems.
Cryptography is the science of communicating information securely from one source to another. You may not notice the daily usage of cryptography in your own life, but its importance cannot be understated. Today, cryptography is widely used throughout communication and payment systems such as e-commerce websites, cell-phones, credit cards, and computer passwords. The goal of using cryptography is to prevent third parties from gaining access to personal data. Today, sensitive information such as bank account details or social security numbers can be entered online thanks to cryptography and its ability to create a secure means of transmitting data. As hacking techniques and identity theft become more sophisticated, cryptography will become one of the most important security measures in protecting personal data.

Principles of Cryptography

Cryptography has three main goals for providing security. First among these is data integrity. When sending messages between two sources, the recipient of the message should be capable of distinguishing whether or not the message was tampered with. In other words, the recipient should be able to discern whether or not a particular part of the message has been falsified. The second goal in maintaining secure communications is authentication. When a message is received, the recipient should be able to verify who the sender is. Finally, cryptography also aims to solidify non-repudiation- meaning that after a message is delivered, the sender should not be capable of refuting that they were the original author [4]. Successful cryptography must accomplish all of these goals: integrity, authentication, and nonrepudiation. For messages written with pen on paper, it is relatively easy to accomplish these goals as personal signatures provide a means for verifying the original author and his or her intent. However, as we continue our advancement into a digital era of communication, meeting the goals of cryptography becomes much more difficult.

History of Cryptography

The practice of cryptography has been around for centuries, and examples of encrypting messages have been dated all the way back to 1900 B.C.E in Egypt. The Atbash cipher was used to encrypt Hebrew messages by replacing the first letter of the Hebrew alphabet with the last letter, the second letter with the second to last, and so on until the alphabet is effectively reversed [1]. A cipher is the set of instructions for encrypting a message, and a “key” is the clue on how to effectively decrypt and read the message. One of the most famous examples of cryptography was what is known as Caesar’s cipher. Julius Caesar would encrypt his messages to his generals by using a substitution cipher in which each letter of the alphabet is shifted a certain number of positions. In this case, Caesar shifted each letter by 3 so that he could securely send messages to his officers, whom he entrusted with the key to deciphering these messages (Fig. 1). The word “cryptography,” for example, would instead be written as “fubswrjudskb”.
P. Thorsteinson and G. A. G. Ganesh/Prentice Hall PTR
Figure 1: Demonstrates a substitution cipher with a shift of 3. Each arrow points to the corresponding letter in the shifted alphabet [3].