[1] Do Problems 1, 7 p. 107.

[2] Using the encryption method discussed in class I encrypted a plaintext message. Recall that the encryption works by taking the number x of a letter (as specified below) and finding the number y of the encrypted letter, using the formula y ≡ x

a b c d e f g h i j k l m n o p q r s t u v w x y z 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 27

Here is the encrypted message I got using e = 25 as the encryption exponent:

meb fxvb, oujb czyub buaxeyu nxglha ozglxo mahjkf? zb zf buh hjfb jgl reczhb zf buh feg.

The decryption exponent d turns out to be 9. I.e., you can find x given y using the formula x ≡ y

For example, m is letter number 14, so to find what letter it was originally, we compute 14

Just plug in the variables m, n and a, and you will get back the value of m

Enter m:

Enter a:

Enter n: