Why Is This Code Difficult To Break In

Why Is This Code Difficult To Break? In this encryption scheme, letters are input and then encrypted in the following way: Each letter is assigned a numerical value. “A” is assigned a value of 1, “B” is assigned a value of 2, C = 3, and so on for all the letters of the alphabet up through Z = 26. Each value is then modified in the following way: First, the number is subtracted from 27. Then, the number is increased by 2. If the increased value is greater than 26, the value is divided by 26 and we use the remainder in a process known as mod-26 arithmetic. The values are mapped back into letters. So a value of 3 would be mapped to the letter C. Example: The letters of the word ZAP are mapped to the numbers 26, 1, 16. These values are subtracted from 27 to give 1, 26, 11. Then each number is increased by 2 using mod-26 arithmetic to result in 3, 2, 13. The values 3, 2, 8 are then mapped back to the letters CBM. Can You Think of a Way To Break This Code?

ANSWER: Although, a little difficult to recognize, one could discover this pattern by comparing two lists of the alphabet with the bottom list containing letters in reverse order. We shift the bottom list until the letters CBM correspond to some real word. In this case, moving the bottom list 2 to the right makes CBM correspond to ZAP as shown below. ZAP is encrypted as CBM This mean we transpose the letter values (subtract from 27) and then add 2 to the letter value. For More Info, See A Tough Code To Break