Question

Encrypt the message APPLES AND ORANGES using a shift chipper with key k=13 .

Short answer

The encrypted message for APPLES AND ORANGES is NCCYRF NAQ BENATRF.

Step-by-step solution

Encryption function for shift chipper

A shift chipper is a private key because when you know the encryption key , then the encryption function is $f\left(p\right)=(p+k)mod26$.

Encrypt the message APPLES AND ORANGES by shift chipper

We have given that key$k=13$

So, the encryption function is $f\left(p\right)=(p+13)mod26$.

Now, also we know that code for alphabet is

$$\begin{gathered} A=0,B=1,C=2,D=3,E=4,F=5,G=6,H=7,I=8,J=9,K=10, \\ L=11,M=12,N=13,O=14,P=15,Q=16,R=17,S=18, \\ T=19,U=20,V=21,W=22,X=23,Y=24,Z=25 \end{gathered}$$

So, we get

$01515114180133141701364$

Now, we have an encryption key k=13

So, by encryption function we get,

‘$$\begin{gathered} 13282824173113261627301326191731(mod26) \\ 132224175130161413019175 \end{gathered}$$

So, for given numbers alphabet is given by,

NCCYRF NAQ BENATRF.

Hence, encrypted message for APPLES AND ORANGES is NCCYRF NAQ BENATRF.