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Codes, Ciphers and Secret Messages 
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Post Codes, Ciphers and Secret Messages
This is a really fun way to play with words and sentences and I highly recommend it for students of all ages. The last time I was in Canada I helped my mother with a bunch of books left over from my grandfather's bookstore after he died. I found a book about codes for kids published my Mensa. I went through it and got lots of ideas for simple codes that kids could have fun playing with.

I've used codes in many of my classes and for last summer camp I made an activity completely focused around the idea of finding a secret meeting of international spies. The students solved different types of puzzles and codes to get all the clues about the location, time, etc. It was a blast.

You can also teach about the subject in general and talk about how to make invisible ink, etc. The history of the subject is also really interesting. For example, at one time they used to shave the head of the messenger, write on the scalp and wait for the hair to grow back. Obvious not a very urgent message. The messenger could be searched and appear not to be carrying anything. Then on the other side his head could be shaved again.

I will be posting some different ideas in this thread shortly. I hope you enjoy them. I'm certain your students will.


Mon Oct 02, 2006 12:02 am
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The most basic approach is to simply disguise the message. These aren't really codes, but fun nonetheless.

1) One of the easiest ways to disguise a message is to change the first letter of each word into some random letter.

KUST DHANGE YTE BIRST OETTER PF DACH BORD.

It's great for word recognition and for sounding out partial words. Which is a very valuable language skill. They are easy to make, too.

2) Another great disguise is to take out all the vowels. The is a game called Squeeze Phrase based on this idea and this a pretty good game idea as well. It can be used for any vocabulary set and is also fun.

LK T THS MSSG. WHT DOS T SY?

3) Of course anagrams are fun, too. Scramble the letters of each word in a sentence and let them work it out.

HTAW SI ERTREB -- GIHNLSE RO HMTA?

4) Or just write the whole sentence backwards. Obviously putting in punctuation makes it too easy.

SDRAWKCAB NETTIRW SI EGASSEM SIHT


Mon Oct 02, 2006 12:22 am
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Not all codes, ciphers and secret messages have to be written.

Last year I taught my elementary school kids Pig Latin. A wonderful phonics exercise to encode and decode words and phrases. It sounds funny for them and they had a ball making up sentences and practicing them and letting the others try to figure out what they were saying.

Pronouncing words backwards is also fun. Try a game centered around the idea of being the first to figure out a backwards word. I give one clue (for example:city) and then say the word a few times. Not fun for those who live in SALLAD, Texas (one or two L's--it all sounds the same backwards).


Last edited by barnett7ya on Mon Oct 02, 2006 5:17 am, edited 1 time in total.



Mon Oct 02, 2006 12:45 am
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One of the oldest and simplest substitution codes was made by Julius Caesar. He would shift each letter by three places. So CAT would become FDW. Of course it is more fun to allow more possibilities. To do this make a code wheel which was two wheels (one small than the other) that are attached through the centre. They are each divided into 26 pie-shaped pieces for each letter of the alphabet. This gives the option for having 25 different codes with each having a different key (example: A=D in Caesar's case). The wheel can first be used to practice encoding words and sentences and then be used to decode with the key given in advance.

Once they are good at using the wheel it is time to learn about some basic cryptology and some simple facts about English.

English has only two words which have only one letter: the artice "a" and the pronoun "I". So if a secret message has some one letter words in it this fact will be very helpful in finding the key (because they will not be given the key and will have to find it themselves). They can set their wheels to A=the one letter word and see if the message makes sense when decoded. If not they can try I=the one letter word.

If there are no one letter words then they will have to work with 2 or 3-letter words. I teach them that some words are very common in English and together we make a list of such words. And we also look at which letters are most common in English and especially in these common 2 and 3-letter words.

Another good side effect is that my students can play Hangman better now that they know that X, Q and J and not such good letters to guess when they haven't tried E, T and A based on letter frequency of the English language.


Mon Oct 02, 2006 1:16 am
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Substitution codes can also use numbers.

1) The easiest one has each letter replaced with the number representing the position of the letter in the alphabet.

14.21.13.2.5.18.19/ 1.18.5/ 6.21.14/ 20.15.15

There are other ways to do this. For example, backwards. A=26 and Z=1.

2) A grid can also be used (5x5). The letters of the alphabet are written in the squares of the grid (I and J share a single square). The grid squares are named in a similar manner as in Battleship: A1, D5, etc.

The students can have fun making their own keys and trying to solve each other's codes.


Mon Oct 02, 2006 1:34 am
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Naturally codes can look much more interesting if they use interesting symbols. Some such codes are very common. For example: Morse code, Semaphore and Braille.

A treasure hunt for class can become a lot more mysterious if the clues have to be decoded first and it makes the maps and notes look very cool.

Another great code was used by a mystical sect called the Rosicrucians. There are actually a few different ways to do it. I like the way that has both the tic tac toe grid and the X grid. It just looks better. You can find more information on the internet as it is hard to explain with a picture.

http://library.thinkquest.org/04oct/004 ... cipher.htm


Mon Oct 02, 2006 1:46 am
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The Spartans used a stick that was slightly tapered. They would wrap long thin pieces of parchment around the stick and then write on it. The result being that the message could not be read unless it was wrapped around a stick with the same dimensions and taper. This method was great until one of their officers was killed or captured and then the key was also taken.


Mon Oct 02, 2006 5:26 am
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Ciphers are fun because they involve re-arranging the letters of the message. There are many ways to do this. It usually involves creating some kind of "path" that you must follow when reading the message.

1) Every other letter moved to the end.

The original: MEET ME AFTER SCHOOL

The change in process: M E M A T R C O L
E T E F E S H O

The encoded message: MEMATRCOLETEFESHO

2) The message can be written in a grid (with extra letters to fill in the extra squares in the grid) and then a path chosen.

WHATAREYOU
DOINGAFTER
SCHOOLXXXX

Following a zig-zag to bottom and left to right you get:

WDSCOHAIHONTAGOLAREFXXTYOEXXRU

Other paths could easily be taken. For example a diagonal zig-zag from the upper lefter to the lower right:

WDHAOSCITANHOGREAOLFYOTXXEURXX


Mon Oct 02, 2006 5:48 am
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Those are excellent! I might try some this week with my JHS classes.

_________________
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Mon Oct 02, 2006 7:09 am
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Location: Tohoku Japan
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check this out

http://www.genkienglish.net/davincicode.htm

this is a good code for JHS

ONE CORRECTION
note on answer for 15 should have one more space
ie the word has 4 letters (not 3 as on the download)


Mon Oct 02, 2006 3:52 pm
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