Wafer Encryption - (Candy Grams) Student Materials

STUDENT

WHY DOES THIS PROJECT MATTER?

Figure 1: Martian surface taken from the mars lander. Notice the robot arm extending from the lower right to upper right with an "elbow" joint.

Data transmission or telemetry, modern digital computers, recording and playback devices, plus a host of other devices rely on encrypting or coding numbers and letters into different forms using simple building blocks that can be easily manipulated by machines. For example, at their most fundamental level, computers can only process a series of "ones" and "zeroes", which, with proper coding, can be made to represent any number and any letter. Representing and transmitting information in this way can have many other advantages besides making it easier for computers to represent letters and numbers.

Figure 2: A solar flare in profile from our sun.

As an example, consider the transmission of data from an unmanned satellite back to earth across the far reaches of space. These data transmissions may be pictures of planet surfaces in digital form such as that shown in figure 1. All data transmissions through space are in the form of radio waves that can be adversely affected by solar flares and sun spots like that shown in figure 2. Since we cannot control the ferocity or frequency of solar activity, how do scientists ensure that those wondrous pictures of far off planets make it back to earth without getting garbled? With an efficient encoding scheme, the satellite converts the picture into a small, tight electronic "package." Then it sends small pieces of this package at intervals back to earth. Attached to each package transmission is a "verification code" that lets earth bound computers make sure that they received a good, unaltered package of data. If solar activity happened to garble the data, then the scientists' computers request the satellite to re transmit the data. If the encoding scheme is robust enough, the earth based telemetry equipment can correct the error. This is one way we reject extraneous noise and interference from transmitted data.

WHAT ARE WE SUPPOSED TO DO?

Although you would find it challenging, you are not expected to program a computer to receive telemetry from the Voyager spacecraft. That would take more time than we can afford, and it has already been done. What you and your team must do is to devise a coding and transmission system that allows you to transmit information (words and numbers) using only SweetTart candies. The SweetTart candies are an affordable substitute for expensive satellite telemetry equipment, and you and your team members are the best and fastest computers that we have available.

You and all your teammates need to devise and remember some type of coding system. You are in essence programming a computer - your own mind! After committing the code to memory, your team will split with half the members going into another room. The only contact with the other half of your team will be by encoding and decoding messages made up of SweetTarts. Your team must also design a way to transmit your messages. A neutral person will carry your messages between rooms; however, your transmission system design needs to keep the message intact. Each message can have a maximum of 50 letters and numbers.

WHAT EQUIPMENT AND MATERIALS CAN WE USE?

You will be given 180 SweetTarts (15 twelve packs) which come in six assorted colors. The candy may not be marked or altered in any way. The wrappers may be re-used, and a quantity of plain unmarked paper will be available to help in the design of a simple transmission system. A single open book may also be used to help arrange the candy during encoding and decoding. Both team halves are allowed to use paper and pencil as needed as long as nothing is written down in advance of sending or receiving a message.

HOW WILL WE KNOW HOW WELL WE HAVE SUCCEEDED?

The basic performance requirement is to transmit a message provided by the instructor in an understandable form with minimal errors. To determine superior performance, the length of time (in minutes) to encode and decode the message without any errors will be recorded. A two minute penalty will be added for each incorrect digit. Teams with the lowest scores will attain the superior performance rating.

WHAT ELSE WOULD BE USEFUL TO KNOW?

Many devices use binary coding, which might be appropriate if you had only two colors of candies. A regular number which had been coded in a binary system might look like this made up of only ones and zeroes, for example:

101110

Each digit indicates the presence or absence of parts of the number that can represented as 2 raised to some power (0, 1, 2, 3, and so on), with the low powers starting on the right. In this example, there are zero 2 's (in the first place holder, 0) + one 2 (in the second place holder, ) + one 2 (in the third place holder, ) + one 2 (in the fourth place holder, ) + no 2's (in the fifth place holder, 0) + one 2 (in the sixth place holder, ). Therefore, the base ten number being represented is:

0 + 2 + 4 + 8 + 0 + 32 = 46.

Other number-based systems can also be devised when more than two choices are available. Why do computers use a binary system? Since current computers are based on electric circuits, it is easiest to consider an electric circuit as being off (0) or on (1), thus the easiest numbering system for computers is a binary one. How do computers work with letters and numbers? All current computers use a table that assigns each symbol, whether a letter, number, punctuation mark, or other symbol, to a binary number. Then when the computer needs to display a symbol on the computer screen, it takes the binary number and looks up the actual symbol for that binary number from this table. Most computers use one of two tables, either ASCII or EBCDIC. Computer manufacturers are currently building a new table that will give computers the ability to display symbols from more languages such as Japanese and Chinese.

Electronic ways of sending and receiving messages have been around for over one hundred years with the telegraph, invented by Samuel Morse, being the most successful. The telegraph was as instrumental in linking both coasts of the United States along with rest of the world in the 19th century. Electronic communication has come along way since then, but if you think about it, these typewritten words are another form of encoding words. Therefore, you are actually inventing a new form of communication, perhaps the most tasty form yet invented by humans! Remember - don't eat your messages until after you have read them.

Have fun!

Engineers do.