How does the code from Chapter 28 work?

It's RSA encryption with a key of 5. To put it in the simplest way possible:

Bring all the numbers to the fifth power, then minus it 의해 multiples of 26 until 당신 get any number 1-26.

2 18 3 5 14 10 15 becomes:

6 18 9 5 14 4 19

Using (A = 1, B = 2, C = 3, ...Z=26) we get:
F R I E N D S

Examples using the smaller numbers:

2^5 = 32 , 32 - 26 = 6 = F

3^5 243, 243 -26(9) = 9 = I

5^5 =3125 , 3125 - 26(120) = 5 = E

If 당신 think about it, it's actually quite simple really. Basically, each number represents a letter. In other words, 1=A, 2=B, 3=C, and so on. If 당신 still don't get it, 당신 can always write the letters and write the numbers above it so 당신 can get a better picture. Believe me the first time I saw the code I couldn't understand it at all until Kurosaki solved it, that's when everything fall into place. Hope this helps!