Introduction: A Fast and Flat Coding Machine

Picture of A Fast and Flat Coding Machine

When I saw the cryptex Instructable ( I thought: "I will make something like that with my grandson this summer to generate coded messages". He is smart with his hands and he will love building one. I also realized that if we were to play spies, I should have my own... I did not want to have one that he could compare with his, so I decided to make something quite different. Since I have some experience with sliding rules I decided that my machine would be flat.

Step 1: You Only Need

Picture of You Only Need

- a piece of cardboard, about 2.5 or 3mm thick and 10x20cm large
- glue
- a sharp cutter knife (and a rule!)
- the template (flatcryptex.pdf)

Step 2: Prepare the Base Material

Picture of Prepare the Base Material

- Download the template
- Print the template
- Paste the template on the cardboard sheet
- LET DRY (over night, to be sure!)
- As you can read on the template at this step, you will have 3 layers (bottom, middle, top)
- Crop, but do not harm yourself with the knife

Step 3: Separate the Pieces

Picture of Separate the Pieces

When you're sure it is really dried, separate the pieces by cutting along the horizontal black lines. Be careful: the cardboard is thick, so do not make any false move that might harm your fingers!

Step 4: Add the Middle Layer Guides

Picture of Add the Middle Layer Guides

Put some glue on the bottom layer pink zones and paste the guides from the middle layer. Check that the central piece from the middle layer can slide easily between the guides.

Let dry (one hour should be enough this time).

Step 5: Add the Top Guides

Picture of Add the Top Guides

Put some glue on the middle guides pink zones and paste the top guides. Once again be sure the central top piece can slide easily between them.

Let dry (you knew that, didn't you?)

Step 6: Fix the Central Part of the Rule

Picture of Fix the Central Part of the Rule

Put some glue on the pink zone of the middle central part and paste the top central part on it. Dit I say "Let dry"?

OK, this is only a fast done object for my summer vacation with my grand kids. If you have time, do the same with some nice wood (or aluminum). Print, paint, or engrave. I would be interested in seeing pictures of your results.

Step 7: How to Use It

Picture of How to Use It

I am sure you know exactly how to use it, but I must be complete...

Such a coding machine is designed to use a Caesar's code encryption, which is an alphabet shifting. So let's say you want to use a +6 shift. As shown on the picture, C will become I. Or, talking about my name:

"PAPYDOM" would be encrypted into "VGVQJUE"

Pro: fits in my pocket
Con: you can not read a whole word, as with a cylindrical cryptex. You must read letter by letter!


ice400 (author)2015-05-19

This 'ible is so cool. I will be making loads more of these. The idea is great ???

andrewp12 (author)2015-03-25


DUO0037 (author)2013-08-15

This is cool!

acoleman3 (author)2011-12-03

im gonna make one from 3mm (1/8in) aluminium and rivet the pieces together, using glue only to affix the labels.

Papydom (author)acoleman32011-12-09

I'd love to see one made out of aluminium. Can you send a picture?

acoleman3 (author)Papydom2011-12-17

oh sorry, i forgot about my project idea and this page until now. this next month ill be able to get the materials, including the pop rivets. heh....i still have teh pdf.

acoleman3 (author)acoleman32011-12-03

of course ill need to make a top/bottom margin space for the rivets, but that'll be easy peasy for me.

skidemon455 (author)2011-12-09

cool but is it ok to use corregated card for it instead of solid

carsoncool (author)2011-09-24

Wow. This is pure genius. I remember this is the 'ible that made me decide to join this community. I've forgotten about it until now. I'm making it as i speak. I'll post a pic when im done!

carsoncool (author)carsoncool2011-09-24

here it is!

Papydom (author)carsoncool2011-09-26

I saw it on your page. Well done! Maybe you put a little bit too much glue, but it was the same for me the first time I made a book cover. I was not used to glue on cardboard and I had to start again from the beginning. But if your rule can slide, it's just great. Keep on making/building/hacking, it's so fun!

carsoncool (author)Papydom2011-09-26

Thanks for the feedback! It slides well, and i cant wait to do more!

nutsandbolts_64 (author)2010-07-11

I've been looking at this for a long time. I feel like I'm gonna make this any time now...

but you didnt....

Hey! I forgot about this project a long time ago... Maybe I'll make it sometime this break. I'm gonna make it out of my failed math project (by failed I meant the second version which I didn't use).

ultrafreak128 (author)2010-07-21

Great design! i have actually completed one out of balsa wood.

gupper2 (author)2009-08-09

My family an I love the design. So far I've made two out of cardboard (one for my father and one for my brother) and I'm working on a third out of balsa wood to aid in the sliding between the pieces Thank you for you great ideas!

Papydom (author)gupper22009-09-09

How about sending a picture of the results?

gupper2 (author)Papydom2010-02-27

 sorry i took so long to comment back.
I'll make sure I do!

Cubie2 (author)2009-12-13

The Cryptex is completely different but good job!

D.L.H. (author)2009-09-06

Do we have to use cardboard can we also use wood like a thin sheet of ply wood ? Other than that it is a cool idea,

Papydom (author)D.L.H.2009-09-09

Of course you can try any other material. In fact, I would be very interested in seeing what it looks like when made out of wood or aluminium. As you can see in the post just under yours, gupper2 is working on making one out of balsa wood. I think it would be nice also to maqke one out of electronic circuit board.

conrad2468 (author)2009-07-16

How would you write a program that changes all your letters into other letters that can then be decoded?

Papydom (author)conrad24682009-07-16

Easy enough... Open an EXCEL sheet. You will use the first line to write the sentence you want to decode (1 letter by cell). Each line under this one will spell the sentence of the preceding line with a +1 shift. Do that by putting the "=CAR(CODE(n°of upper cell)+1)" function in each cell until line 28.
From line 29 do the same with a -1 shift. Then write the coded message on the first line: all the following lines will change. Find the one that makes sense: that's all!
If you're not sure how to prepare the EXCEL sheet, just download my template (
You can try it on this message:
y n u x z e s k y y g m k y e g x k e n g x j e t u f

Of course you can use the same sheet for coding AND decoding.

thepelton (author)Papydom2009-08-06

One thing about straight letter substitution is that it can be decoded by knowing certain things about the English language. First, the ten most common letters used in the English language are, in sequence, ETAONIRSHDL. If you have watched "Wheel of Fortune" a lot, you see those letters come up all the time. Second, there are only three words that have one letter in them- A, I, O, and O is not used that much unless the writer is writing in a style like that of Shakespeare. You should read "Sherlock Holmes: Mystery of the Dancing Men".

thepelton (author)2009-07-16

now, I am working on perfecting one of these in a circular mode. The problem I have been having with it however is spacing. Everything has to be evenly spaced, and the letter "I" is the narrowest one. Perhaps I can post you a picture when I have perfected it..

Papydom (author)thepelton2009-07-17

I had the same problem with my linear slide rule. So, instead of using a text editor to generate the lines of letters, I used an excel sheet (well... in fact it was so I could define precisely the size of the cells and have them be the same width. If I were to make a circular abacus, I think I would use a good image editor software like the GIMP, and use a list of 36 signs (26 letters + space + numbers except 0) because it is easy to ask the software to turn by 10 degrees and then draw a small line (and write a letter). Please send a picture when you are finished!

thepelton (author)Papydom2009-07-17

One thing I should add is that I am making it with a double alphabet (52 characters). That way you can just line one alphabet up under another almost anywhere along the way. I still have to work on the spacing.

Papydom (author)thepelton2009-07-18

What do you mean by "a double alphabet"? If it is circular, the inner list of signs (alphabet +numbers, for instance) is always facing the outer same list. If your list is N signs long, shifting by N-1 steps is equivalent to shifting by -1, so there is no need to double it.

thepelton (author)Papydom2009-07-18

I did it that way so that there was one letter lined up on the code section with a letter on the original even at the ends of the alphabet. I suppose I could make the whole thing a single circular piece, but there are 26 letters in the alphabet, and I'm not sure how to divide a circle into 26 even parts.

Papydom (author)thepelton2009-07-19

Well, to tell the truth, this is the reason why I suggested 36 signs in my former answer... Rotating an image by 10 degrees is easy with a good graphic editor software like The GIMP (or Photoshop, or many other products). You draw 2 circles, a short horizontal line between the circles, copy that line, rotate 10°, paste the line, paste, rotate, paste, rotate... If you want to stick to 26 letters, you have to rotate by 13.85°...

thepelton (author)Papydom2009-07-20

That's a little difficult. I was reworking my idea as a straight decoder the other day.

Papydom (author)thepelton2009-07-20

I hate giving advices that I would not be able to follow myself, so I gave it a fast try. You can find the template I realized at this address ( I must admit I did not write all the letters, but all the cells are ready. I figure that if you are to use some sort of axis (a bolt, or a rivet, etc.) you do not have to use the "middle layer". It is necessary only if you just want to use cardboard and glue.

thepelton (author)Papydom2009-08-06

I still plan on working the whole thing out, and making a photo of it that I can post.

Papydom (author)thepelton2009-07-20

P.S. I added 2 holes on the top layer for easier manipulation

thepelton (author)Papydom2009-07-22

So did I.

zimmemic25 (author)thepelton2009-08-06

you dont know how to divide 360 by 26? BC says its "13.84615384615384615384", so i'd use 13.8 degrees between the letters...

zimmemic25 (author)Papydom2009-08-06

i often use Inkscape for such text-alignments. just make a path, align a text object to it, edit it, and print/export.

Fred82664 (author)2009-07-21

this is a cool ible and one can use any type of creator instead of the alphabet say Binary or Oct numbers and letters hehehehe make it harder to crack the list is endless on what one can code it on. it depends on just how creative the builder can be just forget what you use for a key

heathbar64 (author)2009-07-16

If I may share a pet peeve, I can't stand the instruction to download and print this. I want to know how to figure out and do it myself. This allows for adaptation, and broadening the mind, rather than just copying.

Papydom (author)heathbar642009-07-17

Well, this sounds like a very positive state of mind and I can do nothing but agree with you. So you can either figure this out just by looking at the pictures or find a little help in my answer to thepelton (look a little higher in the comments list). My principles were: 1- Have an alphabet shifted along another one (principle of a slide rule) 2- It must work even if it is completely shifted (letter "a" facing last sign of your list) 3- If the rule seems too long, divide its length by 2 by using the upper side AND the lower side 4- You do not really need to code the numbers (0 to 9): use the latin numbers in your messages ("xviii" stands for "18"), but "space" can be useful and "?" can be meaningful 5- Remember that a shift of +27 equals a shift of -1 if you have a list of 28 signs, which is my case Now, have your own design!

heathbar64 (author)Papydom2009-07-18

Thanks for your response. Yes this paricular project is pretty easy to figure out, my comment was more general in nature. I've seen it done a lot. I do plan on making one of these soon to use with my daughter.

thepelton (author)Papydom2009-07-18

I found I could get a cheap flash drive locally and copy interesting instructables off the site, and put them on the flash drive so I could read them at my leisure off my home computer with no internet. It is 2 gigs and cost 7 dollars US.

sergeant flynn (author)2009-07-17

Very nice code device . However , since I learnt the Morse Code I cannot get away from it . `ever tried to learn that code ? It`s interesting . I`m not criticising just commenting . Keep up the good work . Regards,Sergeant Flynn .

jsgraham (author)2009-07-16

these would be perfect for a puzzle geocache.

mashedpotato13 (author)2009-07-15

This is also known as a "Caeser Shift".

THANKYOU-I was racking my brain trying to remember the first word, its "Caesar Shift", Ar, not Er, but close enough to jog my memory! thanks lol.

sooner_designer (author)2009-07-16

Congratulations on such a fun instructable! You should definitely be proud. You & your grandson will undoubtedly have tons of fun & memories to last a lifetime.

kokyuho (author)2009-07-16

One of my little guys is learning to read. This will be a fun addition to our practice. Thanks!

cory.smith (author)2009-07-15

I think that this is a really great instructable!

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