The History and Mathematics of Codes and Code Breaking

Month: August 2018

Cryptography for different types of people

In the era of rapid technological advancement, the use of cryptography has become an important factor in protecting corporate employees and their customers’ personal information and privacy. Actually, not only the corporates use the cryptography, we can also see the cryptography appears in our daily life.

In Chapter 1 of The Code Book, the author use many examples of well-resourced people such as Mary Queen, the leader of Greece and Persia, and many other types of people who are very important for the country or the security of the country.

In China, there are also these types of the cipher by using in the ancient. “Yin Fu” can be regarded as the earliest military password. When using the two parts, each party will perform half of it to verify the true and the false. The Yin is different in length and length, representing the corresponding intelligence. There is no text on it, even if the enemy seizes it, it cannot be deciphered. In conjunction with the Yin Fu, there is also a “Yinshu“, which is to write a complete piece of information into three pieces and send them separately. After receiving the complete information, the recipients spliced and read the information.

But why should the author use these types of examples? Are there only these people use the cipher in the daily life? The answer is absolutely not. People also use the cipher in their daily life.

In ancient Chinese folk, people used gossip to represent weather, marriage, health, etc. The writing of Chinese words is very complex in ancient. So people use different combinations of gossip represent different pieces of information, there will be countless types of ciphers, but people only need to understand and get the key of the cipher according to the parts they need.

In this example, we can see that not only the well-resourced people use the cipher in their communications, the civilians also use the cipher in their daily life. The reason why most of the well-resourced people’s examples are given is these types of ciphers change the world. In other words, these ciphers have some significant influences. Also we can say they survived those ages.

A Weak Cipher Turned Enemy’s Advantage

The quote “weak encryption can be worse than no encryption at all” describes the phenomenon in which sender of an encrypted message is more likely to state clearly and in detail his or her intentions than when writing a unencrypted message with full knowledge the enemy will be inspecting the text. When writing an unencrypted message, the sender will be more inclined to make the contents of the message vague so it is understood by the receiver but confusing to the interceptor. The sender would also take caution not to reveal any secrets in the message which could benefit the enemy or implicate the sender and allies because the sender is acutely aware of the lack of encryption. However, when a text is encrypted the sender has faith in the security of the encryption and writes messages believing the enemy will not be able to interpret the text. As the in case of Queen Mary’s cipher, she and Anthony Babington did not consider the possibility their cipher could be broken and thus, they communicated their plans of revolt explicitly. Furthermore, weak encryption in particular is dangerous because it can be easily cracked and used by the enemy to deceive the correspondents. This is perfectly illustrated in the case of Queen Mary’s cipher which was broken by Thomas Phelippes and used against Queen Mary and Babington to incriminate Babington’s men. 

This implies for those who encrypt secret messages, they should still communicate vaguely, as though their messages are not encrypted and are being inspected by enemy eyes before reaching the receiver. Additionally, correspondents of encrypted messages should be cautious when writing implicating secrets, as Babington was not, resulting in the capture of his men. Babington could have better protected the identities of his men by describing their qualities in his message without revealing their names. When a cipher is used, the strength of its security should be kept in mind, as a weak cipher could become an enemy’s advantage. As the cipher of Mary Queen demonstrates, unsuspecting faith in the security of a cipher can be more dangerous than using no cipher.

Blog Assignment #1

For your first blog assignment, write a post between 200 and 400 words that responds to one of the reading questions for Singh Chapter 1.

Please give your post a descriptive title, and use the “Student Posts” category for your post. Also, give your post at least three tags, where each tag is a word or very short phrase (no more than three words) that describe the post’s content. You’re encouraged to use tags already in the system if they apply to your post.

Your post is due by 9:00 a.m. on Monday, August 27th. If you have any questions about sharing your first post here on the blog, don’t hesitate to ask.

Here are some basic instructions for posting to WordPress that you might find useful. Also, via xkcd, here’s the secret to using any kind of computer technology.

Image: “Ghost Writer,” by me, Flickr (CC)


I’m excited to teach “Cryptography: The History and Mathematics of Codes and Ciphers” again this fall. It’s my favorite course to teach, and I hope you find it interesting, too.

Here’s a copy of the Fall 2018 syllabus.  Please read this before class on Friday, when we’ll talk about various aspects of the course and I’ll take your questions on the syllabus.

On the Contact page, you’ll find directions to my office, which you’ll need for the “get to know you meetings” you signed up for next week. Be sure to give yourself a few extra minutes to find my office the first time, and feel free to call the Center for Teaching (where I work) if you get lost: 615-322-7290.

I shared a few news stories in class yesterday. I’ll link to them here, in case you want to read them, but I’ll note that they’re also saved in our Diigo bookmark group. Be sure to request access to that group, as outlined in the course syllabus.

I’ll also remind you that you should read the first chapter in our textbook, The Code Book by Simon Singh, before class on Monday. We’ll talk about other upcoming assignments during class on Friday.

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