Add a passphrase generation mechanism (#12)

Based on EFF's wordlist
The wordlist was selected based on arguments mentionned in
https://www.eff.org/deeplinks/2016/07/new-wordlists-random-passphrases
over Arnold Reinhold's Diceware list from 1995 such as avoid short,
deused or diffcult to pronounce words

src/services/passwordGeneration.service.ts

@@ -7,6 +7,8 @@ import {
 } from '../abstractions/passwordGeneration.service';
 import { StorageService } from '../abstractions/storage.service';
 
+import { WordList } from '../misc/wordlist';
+
 const DefaultOptions = {
     length: 14,
     ambiguous: false,
@@ -37,6 +39,10 @@ export class PasswordGenerationService implements PasswordGenerationServiceAbstr
         // overload defaults with given options
         const o = Object.assign({}, DefaultOptions, options);
 
+        if (o.generatePassphrase) {
+            return this.generatePassphrase(options);
+        }
+
         // sanitize
         if (o.uppercase && o.minUppercase <= 0) {
             o.minUppercase = 1;
@@ -150,6 +156,18 @@ export class PasswordGenerationService implements PasswordGenerationServiceAbstr
         return password;
     }
 
+    async generatePassphrase(options: any): Promise<string> {
+        const o = Object.assign({}, DefaultOptions, options);
+
+        const listLength = WordList.length - 1;
+        const wordList = new Array(o.numWords);
+        for (let i = 0; i < o.numWords; i++) {
+            const wordindex = await this.cryptoService.randomNumber(0, listLength);
+            wordList[i] = WordList[wordindex];
+        }
+        return wordList.join(' ');
+    }
+
     async getOptions() {
         if (this.optionsCache == null) {
             const options = await this.storageService.get(Keys.options);