Caesar's Cipher is an algorithm that substitutes each letter of the alphabet by shifting the letter by a given key value. For example, a key of 3 would replace A with D, B with E, and so on. As described in https://www.youtube.com/watch?v=6-JiHa-qLPk, it is fairly easy to break an encrypted message if all letters are shifted by the same number. An improved approach is to use a multiple-digit key that would shift each letter in a document by a different amount. The following screenshot from the video shows how a 10-digit key 5182273847 can encrypt "FREE PIZZA IN THE CAFETERIA" into "KSMG RPCHE PS UPG EHIMXLWJI". The first letter F is shifted by 5 and replaced with K. The second letter R is shifted by 1 and replaced with S. The third letter E is shifted by 8 and replaced with M. And so on. Note that the video and the following screenshot from the video did not convert the last three letters properly. The result should be "WJI" instead of "SJB". . IQKE RLF KISMIG L T NIH MIUIO 1 +5 +1 +8 +2 PNAFC NQ QOBG D O R PCHE P SQD 1 F Q T TRE JG RU +7 +5 +2 +7 +3 +8 +4 As we know, a string is a sequence (array) of characters. The circular effect for this improved Caesar's Cipher comes in two forms. O The first circular form applies to a string of digits as the key. In the above example, as we move down the message, we move down the key string. That is, we use 5 as the key for encripting the first letter 'F', 1 as the key for encripting the second letter 'R', and so on. When we get to the 10th letter 'I', 7 is used as a key. After that, for the 11th letter 'N', we circle back to the beginning of the key string and use '5' as the key to encript. The second circular form applies to a string of all alphabets. const string CaesarCipher::ALPHABET = When the "shifting" does not go past the last letter, no circular effect. For example, ● If the letter to be encripted is F and the key is 5, the encripted letter would be K. If the letter to be encripted is E and the key is 2, the encripted letter would be G. ● ● SNE O F U P G V H WR +1 +8 +2 . When the "shifting" go past the last letter, it circular back to the beginning of the alphabet. For example, ● CF|GK|VJ|QH|Z D GHLWKR 1 A E H 1 MIXIL S J B F 1 J N Y M TKIC GJKOZNUL +2 +7 +3 +8 +4 +7+5 +1 +8 5182273847 ● In this lab, you are asked to implement and test the Ciper and Decipher member functions of the CaesarCipher class. We will focus on only the UPPERCASE LETTERS. "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; string cipher (const string&) const; This function takes a string as its parameter and returns an encrypted string by repeatedly applying the appropriate shifting according to the key. For example, in the following code segment, "CJVYB" would be returned by the cipher function. CaesarCipher demo ("35"); cout << demo.cipher("ZESTY") << endl; If the letter to be encripted is T and the key is 7, the encripted letter would be A. If the letter to be encripted is Z and the key is 3, the encripted letter would be C. Z would be encripted into a letter in ALPHABET that is 3 spaces forward, which is C. Note the circular effect of starting from the letter A in the shifting process. E would be encripted into by a letter in ALPHABET that is 5 spaces forward, which is J. S would be encripted into by a letter in ALPHABET that is 3 spaces forward, which is V. Note the circular effect of using 3 as the key after both 3 and 5 have been used. T would be encripted into by a letter in ALPHABET that is 5 spaces forward, which is Y.