MATH10001 Group Project Part I Question 4

Cypher Decryption

From the example, we find that the method to encrypt the code is to list all the letters apperaedin alphabetical order first and then shift the nth letter in the alphabet by n places backwards.

Eg. APPLE

A-1(B) , E -2(G) , L-3(O) , P- 4(T)

i.e. the word APPLE will become BTTOGNow, our task is to decrypt the code FXVXDKXKHVDSHOVDXDMBDKXXFVOKMD We shallbegin with the letter X which is the closest one to Z as it will not represent 2 different letters atthe same time.

According to the frequency X appears in the code (which is an encrypted sentence) . Xshould be one of the vowel and we choose O to test with.

If X is to be transferred from O, O should be the ninth one in alphabetical order and the sameis true for X as well

Lets list the code FXVXDKXKHVDSHOVDXDMBDKXXFVOKMD in alphabetical order. Itwill be BDFHKMOSVXBD etc.X would then be the tenth letter if all the letters appear in thefirst row, therefore one of them must be taken away from the list.

As ,X has been chosen to be O. and the choice for the first three letters BDF are liimted to

B-1(A), D-1(C), D-2(B), F-2(D), F-3(C)

Meanwhile, F is the first letter of the code followed by X which was O originally . generallyspeaking, we would expect it to be a do instead of a co so we choose F to be at second place inthe list.

Now that all the letters between F and X will have their fixed orders, as shown below.

H-3(E), K-4(G), M-5(H), 0-6(I), S-7(L), V-8(N)

The code FXVXDKXKHVDSHOVDXDMBDKXXFVOKMD will beDONO GOGEN LEIN H GOODNIGH

The only two problems left now are B and D. As they are highly likely to appear again after X,we have the following 3 probabilities.

B-10(R), D-10(T), D-11(U)

The first 5 letters seem to be DONOT So D is going to be at the 10th. As B must appear atleast once, we choose it to be the first one which transfers to A

So the final result will beDO NOT GO GENTLE INTO THAT GOOD NIGHT .

By FIPBTCKVRBA (Dylan Thomas)