The Cinco Cipher

Description and overview.

In my last job as a pharmaceutical engineer, one of my I. T. colleagues mentioned to me that ordinary emails are like postcards and anyone can read them. I thought about this and decided to modify an existing design so that I could include in any email that I sent, a number of four letter groups that would be meaningless to anyone except another recipient with an identical coding machine that could decipher them. Rather like the German Enigma machine. As long as each machine is set up for a particular day of the month, from a prearranged list of daily settings.

My project is so called because it is a cipher machine with five wheels and although I originate from the U. K., I now live in Spain hence the “cinco (five)” part of the name......sounded better than “five cipher”.

I originally printed the wheels on the first machine at 140% (grey ABS) for clarity, but the second machine has wheels printed at 100% (blue PETG) and although smaller, actually looks and works much better.

For the construction of one machine:

1. Access to a 3D printer to print the desired wheels.

2. Plywood for mounting the five meshed cog wheels.

3. 5 x Metal pins or bolts to mount the wheels.

4. Stiff card or plastic card.

5. A Dymo tape machine is desirable but not essential for printing the individual letters and card numbers.

6. 2 x map pins or similar to clearly mark the start and end numbers.

7. Mathematical compasses (to aid inscribing the start and end card numbers).

8. Hole punch to suit the wheel hub diameters.

9. Laminator (not essential but aids with durability of the start and end cards).

10. A LOT of patience!!!

This image shows the machine ready to be set up with the appropriate start card, end card and the wheels necessary for a particular day as described on the monthly coding sheet that would be issued to each user.

To make the wheels:

Access the website http://creativecommons.org/licences/by/3.0/ , or alternatively if you have the necessary skills, prepare files for your 3D printer in order to print the necessary wheels applicable to your language requirements (i.e. The number of teeth in the cog wheel that suits the number of characters in your alphabet. e.g. English has 26.)

Construction:

Once the five wheels are printed, they should be laid out, on a centre line, meshed on a piece of wood or other suitable material, but not too tightly so that they can move easily. The centres of each wheel should be marked on the centre line for drilling so that they can be mounted on pins, bolts or other suitable pegs so that once installed, they can all rotate together in a line. It is not possible for me to state measurements for the space between each wheel as this will be dictated by the size of the wheels. Some constructors may wish to make wheels larger or smaller than 100% standard to suit their individual work spaces. At or near the 12 o'clock position of wheels 2, 3 and 4, an arrow should be inscribed for letter indications when coding and decoding, also indicate the orientation of the device by inscribing TOP as, when testing and proof reading my work, my colleague set up everything perfectly, but it was upside down! Easily done if TOP isn't marked.

Start and End card manufacture:

The start and end cards are made of stiff card and numbered using one of the wheels as a reference so that random numbers can be inscribed at each letter/cog on the wheel. Finding the exact centre of wheels 1 and 5 on the card, the compasses should be set for a diameter a little larger than the wheel, enabling a circle to be inscribed that will accommodate each of the 22 numbers. Only 22 numbers can be inscribed as the remaining 4 have meshed with the adjacent wheel. When 2 holes are punched in the exact centre positions, they should line up perfectly with wheels 1, 2 an d4, 5 when installed. As they are interchangeable, it is important that they are made in such a way so as to not obscure the arrow at wheels 2 and 4. Laminating the cards for durability is a good idea. Making them from plastic card is even better!

Suggestion: When selecting random letters and numbers, to avoid patterns, scrabble pieces or similar should be put in a bag and selected at random when making each wheel, noting these down separately for future construction or security improvements (etc. producing extra wheels or start and end cards). On scrabble pieces, I stuck numbers from 1 to 22 on the back of them. A-1, B-2 and so on.

To sum up, this is a very basic machine with only five moving parts and it takes a lot of patience to construct, but once made, you have a secure method of transmitting and receiving vital/secret information.

This image shows the start and end cards in position with the map pins inserted to denote the start and end numbers described on the monthly coding sheet. These will obviously have to be installed first before finally installing the wheels. I cut small sections of the cards on the corners

This image shows the machine with all the necessary cards, wheel positions and number positions as described on the monthly coding sheet for the particular day required.

The machine consists of a base board that supports five, 26 toothed cog wheels that mesh together so that when one wheel turns, they all turn. Each tooth represents a letter of the English alphabet randomly chosen so as to avoid any sequence of letters that might aid unauthorised decryption. The wheels are interchangeable and as each wheel is double sided, this provides ten possible options for each of the five positions on the base board. Each wheel letter pattern for each side is recorded and stored in a safe place. This should give 26power10 (141,167,095,653,376) possible coded outcomes for each plain text letter entered. The security is further enhanced by the addition of 22 possible start and end positions on wheels 1 and 5 respectively. These start and end positions are also randomly chosen and are recorded on, in this case eight interchangeable cards that can be removed from the machine and stored separately for security purposes. So 22power8 (54,875,873,536) x 26power10 (141,167,095,653,376) would give 7,746,667,688,519,076,667,457,536 possible outcomes for each letter entered. It will become obvious that if more security is required, all one has to do is increase the amount of individual cards and/or wheels provided that each machine involved in the encryption/decryption process has the same, identical selection. Again similar to the Enigma machines distributed to the German armed forces during WW2.

It will also have become obvious that this arrangement is not limited to the English alphabet. As the wheels have been 3D printed, wheels can be produced with any number of teeth that the particular alphabet requires. Some machines of this design have 37 teeth per wheel, comprising of 26 letters, numbers 0 to 9 and a decimal point.

Basic Operation:

The machine is in two separate sections. Section 1 consists of wheels 1 to 4. These wheels concern the input and decoding of the plain text message. Wheel 5 provides the coded letter for each letter entered in turn on wheels 1 to 4.

Example:

To code the word “SECRET”, dial up the S at wheel position 1 to appear opposite the given Start number for the day and record on the coding sheet in the row below the S, the letter that appears opposite to the End number on wheel 5. Dial up the E at wheel 2 arrow position and again record the letter that appears at the end number on wheel 5 below the E. Dial up the C at wheel 3 arrow position and record the letter that appears at the End number on wheel 5 in the box below the C. Repeat this process for each letter in the message, building up a series of four letter groups to code the whole message.

To decode a message, this is basically the reverse of the coding process. With the receiving machine set up identically to the transmitting machine, dial up the first letter in the coded group opposite to the End number at wheel 5. Read off the letter that appears opposite to the Start number at wheel 1 and record it on the coding sheet in the row above the first coded letter. Dial up the second coded letter in the coded group, opposite to the Start number at wheel 5 and record the letter that now appears opposite to the arrow at wheel position 2 in the box above the second coded letter. Dial up the Third coded letter in the coded group, opposite to the Start number at wheel 5 and record the letter that now appears opposite to the arrow at wheel position 3 in the box above the third coded letter. Repeat for all remaining coded letters.

It is interesting to note that in this particular case, when coding the word SECRET, the letter S also becomes S when encoded. This is something that the Enigma machine could not do and this flaw eventually added to it's demise. The other advantage of the Cinco Cipher is that it does not require a battery and light bulbs to work.

Please refer to the file below as I can't include tables in this Instructable format.

This file shows a list of double rows, suggesting a basic method of writing down the plain text message in the upper row (wheels 1 to 4) and the corresponding coded letter for each plain text letter, in the lower row (wheel 5). I printed this sheet, as with all my printed files using Open Office (.odt file) and once printed, it is a good idea to laminate it with a heat sealer for the sake of durability if nothing else, wiping it clean after use. Also this reduces the risk of leaving written evidence for a would-be code breaker to find.