crack caesar cipher solution

Author: effedib

challenges/intermediate/crack-caesar-cipher/solution/fdb86/caesar-cipher.ts

@@ -0,0 +1,21 @@
+export function encode(word: string, shift: number) {
+
+  shift = shift % 26;
+  
+  return word.split("").map(caesar => {
+    const ascii: number = caesar.charCodeAt(0);
+    const new_code: number = ascii + shift;
+    if (ascii >= 65 && ascii <= 90) {
+      if (new_code < 65) {return String.fromCharCode(new_code + 26)}
+      if (new_code > 90) {return String.fromCharCode(new_code - 26)}
+      else return String.fromCharCode(new_code)
+    } else if (ascii >= 97 && ascii <= 122) {
+      if (new_code < 97) {return String.fromCharCode(new_code + 26)}
+      if (new_code > 122) {return String.fromCharCode(new_code - 26)}
+      return String.fromCharCode(new_code)
+    } else return caesar;
+  }).join('');
+}
+
+
+export function decode(word: string, shift: number) {return encode(word, -shift)}

challenges/intermediate/crack-caesar-cipher/solution/fdb86/hack-caesar.ts

@@ -0,0 +1,34 @@
+import {encode} from './caesar-cipher'
+import {decode} from './caesar-cipher'
+
+const englishLetterFreq = {'E': 12.70, 'T': 9.06, 'A': 8.17, 'O': 7.51, 'I': 6.97, 'N': 6.75,
+                           'S': 6.33, 'H': 6.09, 'R': 5.99, 'D': 4.25, 'L': 4.03, 'C': 2.78,
+                           'U': 2.76, 'M': 2.41, 'W': 2.36, 'F': 2.23, 'G': 2.02, 'Y': 1.97,
+                           'P': 1.93, 'B': 1.29, 'V': 0.98, 'K': 0.77, 'J': 0.15, 'X': 0.15,
+                           'Q': 0.10, 'Z': 0.07}
+
+const ETAOIN = 'ETAOINSHRDLCUMWFGYPBVKJXQZ'
+
+function getShiftFactor (message: string) {
+
+
+    var letterCount: any = {}
+    const splitted: any = message.toUpperCase().split("")
+
+    for (let letter of splitted) {
+      if (letter.charCodeAt(0) >= 65 && letter.charCodeAt(0) <= 90) {
+        if (letter in letterCount) { letterCount[letter] += 1}  else {letterCount[letter] = 1}
+      }
+    }
+
+    const nums = Object.keys(letterCount).map(o => letterCount[o]);
+    const max = Math.max(...nums);
+    const char = Object.keys(letterCount).find(letter => letterCount[letter] === max)!;
+    
+    return (char.charCodeAt(0) - ETAOIN.charCodeAt(0))
+
+}
+
+export function crackCaesar (message: string) {
+  return decode(message, getShiftFactor(message))
+}

challenges/intermediate/crack-caesar-cipher/solution/fdb86/rwFiles.js

@@ -0,0 +1,25 @@
+"use strict";
+exports.__esModule = true;
+var hack_caesar_1 = require("./hack-caesar");
+var fs = require('fs');
+var folder = '../../cases/';
+var books = ['Shakespeare-Hamlet.txt', 'Shakespeare-Macbeth.txt', 'Shakespeare-Romeo-And-Juliet.txt'];
+function decryptFiles(path) {
+    fs.readFile(path, 'utf8', function (err, data) {
+        if (err) {
+            console.error(err);
+            return;
+        }
+        var decrypted_data = (0, hack_caesar_1.crackCaesar)(data);
+        fs.writeFile(path.slice(0, -4) + '-decrypted.txt', decrypted_data, function (err) {
+            if (err) {
+                console.error(err);
+                return;
+            }
+            console.log('file written successfully');
+        });
+    });
+}
+for (var i in books) {
+    decryptFiles(folder + books[i]);
+}