Invent A Code

ag_misc_code

Develop a code and encode a message
Grades 4-6

Codes are systems of symbols that represent letters or words. Messages written or sent in code can be understood only by others who know the code key. The science of using codes is cryptography. Codes have been used since ancient times to send messages during times of war. Julius Caesar used a simple code to send messages in the first century B.C., while the British ability to decode Germany's secret messages helped the Allies win World War II.

A foreign language can be a type of code. Many ancient languages, including the hieroglyphics of the Egyptians, were written with symbols that were not understandable to archeologists who discovered the writings many centuries later. Egyptian hieroglyphics, the earliest of which date from about 3,000 B.C., comprised a system of writing that used pictographs (simplified pictures of everyday objects). Egyptian hieroglyphics were decoded after the Rosetta Stone was found in Egypt in 1799. This stone bore an inscription from 196 B.C. that was written in both ancient Greek and in hieroglyphics. Scholars, who already knew how to read the Greek, were then able to translate the Egyptian.

Procedure
The teacher provides some simple background information about codes and how they can be used.

An example of a simple alphabet substitution code is presented: the teacher writes the alphabet on the board and assigns a number to each letter (the code key), such that A=1, B=2, etc.

Students use the Blocks to create a simple alphabet substitution code. Instead of numbers being assigned to each letter of the alphabet, the students choose a Block or Block combination (using the stacking tool) for each letter. They should use the ABC tool to label their symbols with the corresponding letters and then print out this key.

Students use the Blocks and their new code to encode a short message.

Preparation
Students should have paper and pencil for scratch work. Pictures or charts of hieroglyphics and a picture of the Rosetta Stone might be interesting for students. Students should be able to print out their work.

Evaluation
Students are evaluated on their understanding and correct use of the coding process. Students should understand the one-to-one correspondence between each symbol they select and each letter of the alphabet. The correct encoding of the message is also assessed.

Students may want to exchange messages and code keys and attempt to decipher each other's messages. The teacher can then evaluate students for both their encoding and decoding skills.

Extensions
Students can make their own cartouches. A cartouche was a ``name tag" for eminent people in ancient Egypt. It consisted of a vertical oval shape with the wearer's name in hieroglyphics. Students can use their Blocks codes to make their names (stacking the symbols on top of each other), then print them out to be cut out and glued on oval paper for personal cartouches.

Ancient languages (and some modern ones) often did not leave spaces between written words, nor did they necessarily move left to right. Students can experiment with their Blocks codes by writing messages up and down, right to left, or in a circular pattern.

Several students (or an entire class) can create and experiment with their own Rosetta Stone. The same message should be placed into two different codes and then printed out. Students are given the key to only one of the codes. Can they figure out all of the symbols in the other code?

Steganography is the art of hiding coded messages so that only the sender and receiver know they are there.  Students can build a scene incorporating elements of their code but make it look like something else, then give their code to a partner and have them find the message in the scene.

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