The Ceasar cipher is a cipher reportedly used by the famous Roman general Julius Ceasar to communicate with his allies. It is a very simple cipher which is easy to encrypt and to decipher. But, how do you use the Ceasar cipher? Well, I can teach you that! First you pick what message you want to encrypt. For example, "The cat jumped over the moon." Then, you need to choose how much you want to shift it. Let's say a right shift by 5. That means A becomes F as the letter is shifted by 5. So, the alphabet which was "ABCDEFGHIJKLMNOPQRSTUVWXYZ" becomes "FGHIJKLMNOPQRSTUVWXYZABCDE." The message becomes "Ymj hfy ozruji tajw ymj rtts." To decrypt is a simple matter of guess and check. One tip you can keep in mind is that in long messages keep an eye out for the most common letter as there is a chance that that letter is "E". The reason for this? Well, it is the most common letter written.
As time moved on the Ceasar cipher proved inadequate as it is easy to decrypt so the Polyalphabetic cipher. A good cipher is a cipher which makes the letter distribution equal. The Polyalphabetic cipher was widely used by the 15th century. Let's encrypt the same message using the Polyalphabetic cipher.
First you need a shift word. Let's say "fiddle". First you need to change the letters in the word into numbers by using the placement of the letter in the alphabet. So, A becomes 1 and B becomes 2. The alphabet which was "ABCDEFGHIJKLMNOPQRSTUVWXYZ" becomes "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26." The shift word becomes "6 9 4 4 12 5." Then you apply it to the message.
T h e c a t j u m p e d o v e r t h e m o o n.
6 9 4 4 12 5 6 9 4 4 12 5 6 9 4 4 12 5 6 9 4 4 12
Then you shift the letter by whatever number is below so "T" is shifted to the right by 6 spaces. The end result is "Zqi gmy pdqtqi ueiv fmk vssz." Why is it better? Well, it uses multiple shifts instead of 1. Now, in order to break any code you need to look for leaks of information. In this case, you can find that the sequence repeats every 6 letters.
I think that using ciphers is an entertaining way to improve your logical skills. You can use this to send secret messages to your friends and you can ask your friends to write back so you can try to decode their message. I got this information from Khan Academy's series of lessons on cryptology.
Picture source: https://commons.wikimedia.org/wiki/File%3AVigen%C3%A8re_square_shading.svg
By Brandon T. Fields (cdated) [Public domain or Public domain], via Wikimedia Commons
As time moved on the Ceasar cipher proved inadequate as it is easy to decrypt so the Polyalphabetic cipher. A good cipher is a cipher which makes the letter distribution equal. The Polyalphabetic cipher was widely used by the 15th century. Let's encrypt the same message using the Polyalphabetic cipher.
 |
| Polyalphabetic table: |
T h e c a t j u m p e d o v e r t h e m o o n.
6 9 4 4 12 5 6 9 4 4 12 5 6 9 4 4 12 5 6 9 4 4 12
Then you shift the letter by whatever number is below so "T" is shifted to the right by 6 spaces. The end result is "Zqi gmy pdqtqi ueiv fmk vssz." Why is it better? Well, it uses multiple shifts instead of 1. Now, in order to break any code you need to look for leaks of information. In this case, you can find that the sequence repeats every 6 letters.
I think that using ciphers is an entertaining way to improve your logical skills. You can use this to send secret messages to your friends and you can ask your friends to write back so you can try to decode their message. I got this information from Khan Academy's series of lessons on cryptology.
Picture source: https://commons.wikimedia.org/wiki/File%3AVigen%C3%A8re_square_shading.svg
By Brandon T. Fields (cdated) [Public domain or Public domain], via Wikimedia Commons
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