Add functions to encrypt and decrypt using a randomly generated pad

index.js

@@ -0,0 +1,35 @@
+const CHARS = [
+  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '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',
+];
+
+function generatePad(string) {
+  const pad = [];
+  for (let i = 0; i < string.length; i++) {
+    const letter = Math.floor(Math.random() * CHARS.length);
+    pad.push(letter);
+  }
+  return pad;
+}
+
+function encrypt(string) {
+  const strippedString = string.replace(/[^A-Z0-9]/g, '');
+  const pad = generatePad(strippedString);
+  return {
+    oneTimePad: pad,
+    encryptedMessage: strippedString.toUpperCase().split('').map((letter, index) => {
+      const letterValue = CHARS.indexOf(letter);
+      const padValue = CHARS.indexOf(pad[index]);
+      return CHARS[(letterValue + padValue) % CHARS.length];
+    }).join(''),
+  };
+}
+
+function decrypt(string, pad) {
+  return string.split('').map((letter, index) => {
+    const letterValue = CHARS.indexOf(letter);
+    const padValue = CHARS.indexOf(pad[index]);
+    return CHARS[(letterValue - padValue) % CHARS.length];
+  }).join('');
+}