Question

using the website repl.it (must be done in Javascript)

PGM #1

Write a Java program that can perform the Caesar cipher for English messages that include both upper and lowercase alphabetic characters. The Caesar cipher replaces each plaintext letter with a different one, by a fixed number of places down the alphabet. The cipher illustrated here uses a left shift of three, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext.

For example

Plaintext: THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.

Ciphertext: QEBNRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD

PGM #2 ROT13:

Cipher Project 2 Create a similar Java program using ROT13 algorithm ROT13 is a common example of a cipher that was used quite frequently on numerous sites. It wasn’t ever really intended to prevent people from reading a message, but rather just to hide text

from the prying eyes. Most online sites use this function to ROT13 a message. Because with ROT13, you are shifting the alphabet 13 places, the same shift will return the text to its original position.

Answer 1

program 1:

main.js:

function main_fun() {

var plain_text = "HELLO WORLD I AM JAVA SRIPT CODER";

var shift = 3;

var encrypted_text = code(plain_text, shift, 'e');

var decrypted_text = code(encrypted_text, shift, 'd');

console.log("Plain Text: " + plain_text);

console.log("Shift: " + shift);

console.log("Encrypted Text: " + encrypted_text);

console.log("Decrypted Text: " + decrypted_text);

}

function code(text, shift, ch) {

var res = [];

if (ch === 'e') {

for (var i = 0; i < text.length; i++) {

if (text.charAt(i) != ' ') {

res[i] = String.fromCharCode(((text.charCodeAt(i) + shift - 65) % 26 + 65));

//shift by 13 positions and store in array of char type

} else

res[i] = ' ';

}

var result = res.join("");

//convert char array to string and return

return result;

} else if (ch === 'd') {

for (var i = 0; i < text.length; i++) {

if (text.charAt(i) != ' ') {

res[i] = String.fromCharCode(((text.charCodeAt(i) - shift + 65) % 26 + 65));

//shift by 13 positions and store in array of char type

} else

res[i] = ' ';

}

var result = res.join("");

//convert char array to string and return

return result;

} else

return null;

}main_fun();

Output:

share un + new repl llanguages 98 talk Sign up Native Browser JavaScript Plain Text: HELLO WORLD I AM JAVA SRIPT CODER Shift: 3 Encrypted Text: KH0OR ZRUOG L DP MDYD VULSW FRGHU Decrypted Text: HELLO WORLD I AM JAVA SRIPT CODER → undefined

Program2:

main.js:

function main_fun() {

var plain_text = "HELLO WORLD I AM JAVA SRIPT CODER";

var encrypted_text = code(plain_text, 13);

var decrypted_text = code(encrypted_text, 13);

console.log("Plain Text: " + plain_text);

console.log("Encrypted Text: " + encrypted_text);

console.log("Decrypted Text: " + decrypted_text);

}

function code(text, shift) {

var res = [];

for (var i = 0; i < text.length; i++) {

if (text.charAt(i) != ' ') {

res[i] = String.fromCharCode(((text.charCodeAt(i) + shift - 65) % 26 + 65));

//shift by 13 positions and store in array of char type

} else

res[i] = ' ';

}

var result = res.join("");

//convert char array to string and return

return result;

}

main_fun();

Output:

share + new repl languages talk Sign up run Native Browser JavaScript Plain Text: HELLO WORLD I AM JAVA SRIPT CODER Encrypted Text: URYYB JBEYQ V NZ WNIN FEVCG PBQRE Decrypted Text: HELLO WORLD I AM JAVA SRIPT CODER undefined