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  193. <li class="toctree-l2"><a class="reference internal" href="../helpers/path_helper.html">Path Helper</a></li>
    194. 

  194. <li class="toctree-l2"><a class="reference internal" href="../helpers/security_helper.html">Security Helper</a></li>
    195. 

  195. <li class="toctree-l2"><a class="reference internal" href="../helpers/smiley_helper.html">Smiley Helper</a></li>
    196. 

  196. <li class="toctree-l2"><a class="reference internal" href="../helpers/string_helper.html">String Helper</a></li>
    197. 

  197. <li class="toctree-l2"><a class="reference internal" href="../helpers/text_helper.html">Text Helper</a></li>
    198. 

  198. <li class="toctree-l2"><a class="reference internal" href="../helpers/typography_helper.html">Typography Helper</a></li>
    199. 

  199. <li class="toctree-l2"><a class="reference internal" href="../helpers/url_helper.html">URL Helper</a></li>
    200. 

  200. <li class="toctree-l2"><a class="reference internal" href="../helpers/xml_helper.html">XML Helper</a></li>
    201. 

  201. </ul>
    202. 

  202. </li>
    203. 

  203. </ul>
    204. 

  204. 

  205.       </div>
    206. 

  206.     
    207. 

  207.       
    208. 

  208.   </div>
    209. 

  209. </div>
    210. 

  210. <div id="nav2">
    211. 

  211.   <a href="#" id="openToc">
    212. 

  212.     <img src="data:image/jpeg;base64,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" title="Toggle Table of Contents" alt="Toggle Table of Contents" />
    213. 

  213.   </a>
    214. 

  214. </div>
    215. 

  215. 

  216.   <div class="wy-grid-for-nav">
    217. 

  217. 

  218.     
    219. 

  219.     <nav data-toggle="wy-nav-shift" class="wy-nav-side">
    220. 

  220.       <div class="wy-side-nav-search">
    221. 

  221.         
    222. 

  222.           <a href="../index.html" class="fa fa-home"> CodeIgniter</a>
    223. 

  223.         
    224. 

  224.         
    225. 

  225. <div role="search">
    226. 

  226.   <form id="rtd-search-form" class="wy-form" action="../search.html" method="get">
    227. 

  227.     <input type="text" name="q" placeholder="Search docs" />
    228. 

  228.     <input type="hidden" name="check_keywords" value="yes" />
    229. 

  229.     <input type="hidden" name="area" value="default" />
    230. 

  230.   </form>
    231. 

  231. </div>
    232. 

  232.       </div>
    233. 

  233. 

  234.       <div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
    235. 

  235.         
    236. 

  236.           
    237. 

  237.           
    238. 

  238.               <ul>
    239. 

  239. <li class="toctree-l1"><a class="reference internal" href="../general/welcome.html">Welcome to CodeIgniter</a></li>
    240. 

  240. </ul>
    241. 

  241. <ul>
    242. 

  242. <li class="toctree-l1"><a class="reference internal" href="../installation/index.html">Installation Instructions</a><ul>
    243. 

  243. <li class="toctree-l2"><a class="reference internal" href="../installation/downloads.html">Downloading CodeIgniter</a></li>
    244. 

  244. <li class="toctree-l2"><a class="reference internal" href="../installation/index.html">Installation Instructions</a></li>
    245. 

  245. <li class="toctree-l2"><a class="reference internal" href="../installation/upgrading.html">Upgrading From a Previous Version</a></li>
    246. 

  246. <li class="toctree-l2"><a class="reference internal" href="../installation/troubleshooting.html">Troubleshooting</a></li>
    247. 

  247. </ul>
    248. 

  248. </li>
    249. 

  249. </ul>
    250. 

  250. <ul>
    251. 

  251. <li class="toctree-l1"><a class="reference internal" href="../overview/index.html">CodeIgniter Overview</a><ul>
    252. 

  252. <li class="toctree-l2"><a class="reference internal" href="../overview/getting_started.html">Getting Started</a></li>
    253. 

  253. <li class="toctree-l2"><a class="reference internal" href="../overview/at_a_glance.html">CodeIgniter at a Glance</a></li>
    254. 

  254. <li class="toctree-l2"><a class="reference internal" href="../overview/features.html">Supported Features</a></li>
    255. 

  255. <li class="toctree-l2"><a class="reference internal" href="../overview/appflow.html">Application Flow Chart</a></li>
    256. 

  256. <li class="toctree-l2"><a class="reference internal" href="../overview/mvc.html">Model-View-Controller</a></li>
    257. 

  257. <li class="toctree-l2"><a class="reference internal" href="../overview/goals.html">Architectural Goals</a></li>
    258. 

  258. </ul>
    259. 

  259. </li>
    260. 

  260. </ul>
    261. 

  261. <ul>
    262. 

  262. <li class="toctree-l1"><a class="reference internal" href="../tutorial/index.html">Tutorial</a><ul>
    263. 

  263. <li class="toctree-l2"><a class="reference internal" href="../tutorial/static_pages.html">Static pages</a></li>
    264. 

  264. <li class="toctree-l2"><a class="reference internal" href="../tutorial/news_section.html">News section</a></li>
    265. 

  265. <li class="toctree-l2"><a class="reference internal" href="../tutorial/create_news_items.html">Create news items</a></li>
    266. 

  266. <li class="toctree-l2"><a class="reference internal" href="../tutorial/conclusion.html">Conclusion</a></li>
    267. 

  267. </ul>
    268. 

  268. </li>
    269. 

  269. </ul>
    270. 

  270. <ul>
    271. 

  271. <li class="toctree-l1"><a class="reference internal" href="../contributing/index.html">Contributing to CodeIgniter</a><ul>
    272. 

  272. <li class="toctree-l2"><a class="reference internal" href="../documentation/index.html">Writing CodeIgniter Documentation</a></li>
    273. 

  273. <li class="toctree-l2"><a class="reference internal" href="../DCO.html">Developer’s Certificate of Origin 1.1</a></li>
    274. 

  274. </ul>
    275. 

  275. </li>
    276. 

  276. </ul>
    277. 

  277. <ul>
    278. 

  278. <li class="toctree-l1"><a class="reference internal" href="../general/index.html">General Topics</a><ul>
    279. 

  279. <li class="toctree-l2"><a class="reference internal" href="../general/urls.html">CodeIgniter URLs</a></li>
    280. 

  280. <li class="toctree-l2"><a class="reference internal" href="../general/controllers.html">Controllers</a></li>
    281. 

  281. <li class="toctree-l2"><a class="reference internal" href="../general/reserved_names.html">Reserved Names</a></li>
    282. 

  282. <li class="toctree-l2"><a class="reference internal" href="../general/views.html">Views</a></li>
    283. 

  283. <li class="toctree-l2"><a class="reference internal" href="../general/models.html">Models</a></li>
    284. 

  284. <li class="toctree-l2"><a class="reference internal" href="../general/helpers.html">Helpers</a></li>
    285. 

  285. <li class="toctree-l2"><a class="reference internal" href="../general/libraries.html">Using CodeIgniter Libraries</a></li>
    286. 

  286. <li class="toctree-l2"><a class="reference internal" href="../general/creating_libraries.html">Creating Libraries</a></li>
    287. 

  287. <li class="toctree-l2"><a class="reference internal" href="../general/drivers.html">Using CodeIgniter Drivers</a></li>
    288. 

  288. <li class="toctree-l2"><a class="reference internal" href="../general/creating_drivers.html">Creating Drivers</a></li>
    289. 

  289. <li class="toctree-l2"><a class="reference internal" href="../general/core_classes.html">Creating Core System Classes</a></li>
    290. 

  290. <li class="toctree-l2"><a class="reference internal" href="../general/ancillary_classes.html">Creating Ancillary Classes</a></li>
    291. 

  291. <li class="toctree-l2"><a class="reference internal" href="../general/hooks.html">Hooks - Extending the Framework Core</a></li>
    292. 

  292. <li class="toctree-l2"><a class="reference internal" href="../general/autoloader.html">Auto-loading Resources</a></li>
    293. 

  293. <li class="toctree-l2"><a class="reference internal" href="../general/common_functions.html">Common Functions</a></li>
    294. 

  294. <li class="toctree-l2"><a class="reference internal" href="../general/compatibility_functions.html">Compatibility Functions</a></li>
    295. 

  295. <li class="toctree-l2"><a class="reference internal" href="../general/routing.html">URI Routing</a></li>
    296. 

  296. <li class="toctree-l2"><a class="reference internal" href="../general/errors.html">Error Handling</a></li>
    297. 

  297. <li class="toctree-l2"><a class="reference internal" href="../general/caching.html">Caching</a></li>
    298. 

  298. <li class="toctree-l2"><a class="reference internal" href="../general/profiling.html">Profiling Your Application</a></li>
    299. 

  299. <li class="toctree-l2"><a class="reference internal" href="../general/cli.html">Running via the CLI</a></li>
    300. 

  300. <li class="toctree-l2"><a class="reference internal" href="../general/managing_apps.html">Managing your Applications</a></li>
    301. 

  301. <li class="toctree-l2"><a class="reference internal" href="../general/environments.html">Handling Multiple Environments</a></li>
    302. 

  302. <li class="toctree-l2"><a class="reference internal" href="../general/alternative_php.html">Alternate PHP Syntax for View Files</a></li>
    303. 

  303. <li class="toctree-l2"><a class="reference internal" href="../general/security.html">Security</a></li>
    304. 

  304. <li class="toctree-l2"><a class="reference internal" href="../general/styleguide.html">PHP Style Guide</a></li>
    305. 

  305. </ul>
    306. 

  306. </li>
    307. 

  307. </ul>
    308. 

  308. <ul class="current">
    309. 

  309. <li class="toctree-l1 current"><a class="reference internal" href="index.html">Libraries</a><ul class="current">
    310. 

  310. <li class="toctree-l2"><a class="reference internal" href="benchmark.html">Benchmarking Class</a></li>
    311. 

  311. <li class="toctree-l2"><a class="reference internal" href="caching.html">Caching Driver</a></li>
    312. 

  312. <li class="toctree-l2"><a class="reference internal" href="calendar.html">Calendaring Class</a></li>
    313. 

  313. <li class="toctree-l2"><a class="reference internal" href="cart.html">Shopping Cart Class</a></li>
    314. 

  314. <li class="toctree-l2"><a class="reference internal" href="config.html">Config Class</a></li>
    315. 

  315. <li class="toctree-l2"><a class="reference internal" href="email.html">Email Class</a></li>
    316. 

  316. <li class="toctree-l2"><a class="reference internal" href="encrypt.html">Encrypt Class</a></li>
    317. 

  317. <li class="toctree-l2 current"><a class="current reference internal" href="#">Encryption Library</a></li>
    318. 

  318. <li class="toctree-l2"><a class="reference internal" href="file_uploading.html">File Uploading Class</a></li>
    319. 

  319. <li class="toctree-l2"><a class="reference internal" href="form_validation.html">Form Validation</a></li>
    320. 

  320. <li class="toctree-l2"><a class="reference internal" href="ftp.html">FTP Class</a></li>
    321. 

  321. <li class="toctree-l2"><a class="reference internal" href="image_lib.html">Image Manipulation Class</a></li>
    322. 

  322. <li class="toctree-l2"><a class="reference internal" href="input.html">Input Class</a></li>
    323. 

  323. <li class="toctree-l2"><a class="reference internal" href="javascript.html">Javascript Class</a></li>
    324. 

  324. <li class="toctree-l2"><a class="reference internal" href="language.html">Language Class</a></li>
    325. 

  325. <li class="toctree-l2"><a class="reference internal" href="loader.html">Loader Class</a></li>
    326. 

  326. <li class="toctree-l2"><a class="reference internal" href="migration.html">Migrations Class</a></li>
    327. 

  327. <li class="toctree-l2"><a class="reference internal" href="output.html">Output Class</a></li>
    328. 

  328. <li class="toctree-l2"><a class="reference internal" href="pagination.html">Pagination Class</a></li>
    329. 

  329. <li class="toctree-l2"><a class="reference internal" href="parser.html">Template Parser Class</a></li>
    330. 

  330. <li class="toctree-l2"><a class="reference internal" href="security.html">Security Class</a></li>
    331. 

  331. <li class="toctree-l2"><a class="reference internal" href="sessions.html">Session Library</a></li>
    332. 

  332. <li class="toctree-l2"><a class="reference internal" href="table.html">HTML Table Class</a></li>
    333. 

  333. <li class="toctree-l2"><a class="reference internal" href="trackback.html">Trackback Class</a></li>
    334. 

  334. <li class="toctree-l2"><a class="reference internal" href="typography.html">Typography Class</a></li>
    335. 

  335. <li class="toctree-l2"><a class="reference internal" href="unit_testing.html">Unit Testing Class</a></li>
    336. 

  336. <li class="toctree-l2"><a class="reference internal" href="uri.html">URI Class</a></li>
    337. 

  337. <li class="toctree-l2"><a class="reference internal" href="user_agent.html">User Agent Class</a></li>
    338. 

  338. <li class="toctree-l2"><a class="reference internal" href="xmlrpc.html">XML-RPC and XML-RPC Server Classes</a></li>
    339. 

  339. <li class="toctree-l2"><a class="reference internal" href="zip.html">Zip Encoding Class</a></li>
    340. 

  340. </ul>
    341. 

  341. </li>
    342. 

  342. </ul>
    343. 

  343. <ul>
    344. 

  344. <li class="toctree-l1"><a class="reference internal" href="../database/index.html">Database Reference</a><ul>
    345. 

  345. <li class="toctree-l2"><a class="reference internal" href="../database/examples.html">Quick Start: Usage Examples</a></li>
    346. 

  346. <li class="toctree-l2"><a class="reference internal" href="../database/configuration.html">Database Configuration</a></li>
    347. 

  347. <li class="toctree-l2"><a class="reference internal" href="../database/connecting.html">Connecting to a Database</a></li>
    348. 

  348. <li class="toctree-l2"><a class="reference internal" href="../database/queries.html">Running Queries</a></li>
    349. 

  349. <li class="toctree-l2"><a class="reference internal" href="../database/results.html">Generating Query Results</a></li>
    350. 

  350. <li class="toctree-l2"><a class="reference internal" href="../database/helpers.html">Query Helper Functions</a></li>
    351. 

  351. <li class="toctree-l2"><a class="reference internal" href="../database/query_builder.html">Query Builder Class</a></li>
    352. 

  352. <li class="toctree-l2"><a class="reference internal" href="../database/transactions.html">Transactions</a></li>
    353. 

  353. <li class="toctree-l2"><a class="reference internal" href="../database/metadata.html">Getting MetaData</a></li>
    354. 

  354. <li class="toctree-l2"><a class="reference internal" href="../database/call_function.html">Custom Function Calls</a></li>
    355. 

  355. <li class="toctree-l2"><a class="reference internal" href="../database/caching.html">Query Caching</a></li>
    356. 

  356. <li class="toctree-l2"><a class="reference internal" href="../database/forge.html">Database Manipulation with Database Forge</a></li>
    357. 

  357. <li class="toctree-l2"><a class="reference internal" href="../database/utilities.html">Database Utilities Class</a></li>
    358. 

  358. <li class="toctree-l2"><a class="reference internal" href="../database/db_driver_reference.html">Database Driver Reference</a></li>
    359. 

  359. </ul>
    360. 

  360. </li>
    361. 

  361. </ul>
    362. 

  362. <ul>
    363. 

  363. <li class="toctree-l1"><a class="reference internal" href="../helpers/index.html">Helpers</a><ul>
    364. 

  364. <li class="toctree-l2"><a class="reference internal" href="../helpers/array_helper.html">Array Helper</a></li>
    365. 

  365. <li class="toctree-l2"><a class="reference internal" href="../helpers/captcha_helper.html">CAPTCHA Helper</a></li>
    366. 

  366. <li class="toctree-l2"><a class="reference internal" href="../helpers/cookie_helper.html">Cookie Helper</a></li>
    367. 

  367. <li class="toctree-l2"><a class="reference internal" href="../helpers/date_helper.html">Date Helper</a></li>
    368. 

  368. <li class="toctree-l2"><a class="reference internal" href="../helpers/directory_helper.html">Directory Helper</a></li>
    369. 

  369. <li class="toctree-l2"><a class="reference internal" href="../helpers/download_helper.html">Download Helper</a></li>
    370. 

  370. <li class="toctree-l2"><a class="reference internal" href="../helpers/email_helper.html">Email Helper</a></li>
    371. 

  371. <li class="toctree-l2"><a class="reference internal" href="../helpers/file_helper.html">File Helper</a></li>
    372. 

  372. <li class="toctree-l2"><a class="reference internal" href="../helpers/form_helper.html">Form Helper</a></li>
    373. 

  373. <li class="toctree-l2"><a class="reference internal" href="../helpers/html_helper.html">HTML Helper</a></li>
    374. 

  374. <li class="toctree-l2"><a class="reference internal" href="../helpers/inflector_helper.html">Inflector Helper</a></li>
    375. 

  375. <li class="toctree-l2"><a class="reference internal" href="../helpers/language_helper.html">Language Helper</a></li>
    376. 

  376. <li class="toctree-l2"><a class="reference internal" href="../helpers/number_helper.html">Number Helper</a></li>
    377. 

  377. <li class="toctree-l2"><a class="reference internal" href="../helpers/path_helper.html">Path Helper</a></li>
    378. 

  378. <li class="toctree-l2"><a class="reference internal" href="../helpers/security_helper.html">Security Helper</a></li>
    379. 

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  425.   <div class="section" id="encryption-library">
    426. 

  426. <h1>Encryption Library<a class="headerlink" href="#encryption-library" title="Permalink to this headline">¶</a></h1>
    427. 

  427. <div class="admonition important">
    428. 

  428. <p class="first admonition-title">Important</p>
    429. 

  429. <p class="last">DO NOT use this or any other <em>encryption</em> library for
    430. 

  430. user password storage! Passwords must be <em>hashed</em> instead, and you
    431. 

  431. should do that via PHP’s own <a class="reference external" href="http://php.net/password">Password Hashing extension</a>.</p>
    432. 

  432. </div>
    433. 

  433. <p>The Encryption Library provides two-way data encryption. To do so in
    434. 

  434. a cryptographically secure way, it utilizes PHP extensions that are
    435. 

  435. unfortunately not always available on all systems.
    436. 

  436. You must meet one of the following dependencies in order to use this
    437. 

  437. library:</p>
    438. 

  438. <ul class="simple">
    439. 

  439. <li><a class="reference external" href="http://php.net/openssl">OpenSSL</a></li>
    440. 

  440. <li><a class="reference external" href="http://php.net/mcrypt">MCrypt</a> (and <cite>MCRYPT_DEV_URANDOM</cite> availability)</li>
    441. 

  441. </ul>
    442. 

  442. <p>If neither of the above dependencies is met, we simply cannot offer
    443. 

  443. you a good enough implementation to meet the high standards required
    444. 

  444. for proper cryptography.</p>
    445. 

  445. <div class="contents local topic" id="contents">
    446. 

  446. <ul class="simple">
    447. 

  447. <li><a class="reference internal" href="#using-the-encryption-library" id="id2">Using the Encryption Library</a><ul>
    448. 

  448. <li><a class="reference internal" href="#initializing-the-class" id="id3">Initializing the Class</a></li>
    449. 

  449. <li><a class="reference internal" href="#default-behavior" id="id4">Default behavior</a></li>
    450. 

  450. <li><a class="reference internal" href="#setting-your-encryption-key" id="id5">Setting your encryption_key</a></li>
    451. 

  451. <li><a class="reference internal" href="#supported-encryption-ciphers-and-modes" id="id6">Supported encryption ciphers and modes</a><ul>
    452. 

  452. <li><a class="reference internal" href="#portable-ciphers" id="id7">Portable ciphers</a></li>
    453. 

  453. <li><a class="reference internal" href="#driver-specific-ciphers" id="id8">Driver-specific ciphers</a></li>
    454. 

  454. <li><a class="reference internal" href="#encryption-modes" id="id9">Encryption modes</a></li>
    455. 

  455. </ul>
    456. 

  456. </li>
    457. 

  457. <li><a class="reference internal" href="#message-length" id="id10">Message Length</a></li>
    458. 

  458. <li><a class="reference internal" href="#configuring-the-library" id="id11">Configuring the library</a></li>
    459. 

  459. <li><a class="reference internal" href="#encrypting-and-decrypting-data" id="id12">Encrypting and decrypting data</a><ul>
    460. 

  460. <li><a class="reference internal" href="#how-it-works" id="id13">How it works</a></li>
    461. 

  461. <li><a class="reference internal" href="#using-custom-parameters" id="id14">Using custom parameters</a></li>
    462. 

  462. <li><a class="reference internal" href="#supported-hmac-authentication-algorithms" id="id15">Supported HMAC authentication algorithms</a></li>
    463. 

  463. </ul>
    464. 

  464. </li>
    465. 

  465. </ul>
    466. 

  466. </li>
    467. 

  467. <li><a class="reference internal" href="#class-reference" id="id16">Class Reference</a></li>
    468. 

  468. </ul>
    469. 

  469. </div>
    470. 

  470. <div class="custom-index container"></div><div class="section" id="using-the-encryption-library">
    471. 

  471. <h2><a class="toc-backref" href="#id2">Using the Encryption Library</a><a class="headerlink" href="#using-the-encryption-library" title="Permalink to this headline">¶</a></h2>
    472. 

  472. <div class="section" id="initializing-the-class">
    473. 

  473. <h3><a class="toc-backref" href="#id3">Initializing the Class</a><a class="headerlink" href="#initializing-the-class" title="Permalink to this headline">¶</a></h3>
    474. 

  474. <p>Like most other classes in CodeIgniter, the Encryption library is
    475. 

  475. initialized in your controller using the <code class="docutils literal"><span class="pre">$this-&gt;load-&gt;library()</span></code>
    476. 

  476. method:</p>
    477. 

  477. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">load</span><span class="o">-&gt;</span><span class="na">library</span><span class="p">(</span><span class="s1">&#39;encryption&#39;</span><span class="p">);</span>
    478. 

  478. </pre></div>
    479. 

  479. </div>
    480. 

  480. <p>Once loaded, the Encryption library object will be available using:</p>
    481. 

  481. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span>
    482. 

  482. </pre></div>
    483. 

  483. </div>
    484. 

  484. </div>
    485. 

  485. <div class="section" id="default-behavior">
    486. 

  486. <h3><a class="toc-backref" href="#id4">Default behavior</a><a class="headerlink" href="#default-behavior" title="Permalink to this headline">¶</a></h3>
    487. 

  487. <p>By default, the Encryption Library will use the AES-128 cipher in CBC
    488. 

  488. mode, using your configured <em>encryption_key</em> and SHA512 HMAC authentication.</p>
    489. 

  489. <div class="admonition note">
    490. 

  490. <p class="first admonition-title">Note</p>
    491. 

  491. <p class="last">AES-128 is chosen both because it is proven to be strong and
    492. 

  492. because of its wide availability across different cryptographic
    493. 

  493. software and programming languages’ APIs.</p>
    494. 

  494. </div>
    495. 

  495. <p>However, the <em>encryption_key</em> is not used as is.</p>
    496. 

  496. <p>If you are somewhat familiar with cryptography, you should already know
    497. 

  497. that a HMAC also requires a secret key and using the same key for both
    498. 

  498. encryption and authentication is a bad practice.</p>
    499. 

  499. <p>Because of that, two separate keys are derived from your already configured
    500. 

  500. <em>encryption_key</em>: one for encryption and one for authentication. This is
    501. 

  501. done via a technique called <a class="reference external" href="http://en.wikipedia.org/wiki/HKDF">HMAC-based Key Derivation Function</a> (HKDF).</p>
    502. 

  502. </div>
    503. 

  503. <div class="section" id="setting-your-encryption-key">
    504. 

  504. <h3><a class="toc-backref" href="#id5">Setting your encryption_key</a><a class="headerlink" href="#setting-your-encryption-key" title="Permalink to this headline">¶</a></h3>
    505. 

  505. <p>An <em>encryption key</em> is a piece of information that controls the
    506. 

  506. cryptographic process and permits a plain-text string to be encrypted,
    507. 

  507. and afterwards - decrypted. It is the secret “ingredient” in the whole
    508. 

  508. process that allows you to be the only one who is able to decrypt data
    509. 

  509. that you’ve decided to hide from the eyes of the public.
    510. 

  510. After one key is used to encrypt data, that same key provides the <strong>only</strong>
    511. 

  511. means to decrypt it, so not only must you chose one carefully, but you
    512. 

  512. must not lose it or you will also lose access to the data.</p>
    513. 

  513. <p>It must be noted that to ensure maximum security, such key <em>should</em> not
    514. 

  514. only be as strong as possible, but also often changed. Such behavior
    515. 

  515. however is rarely practical or possible to implement, and that is why
    516. 

  516. CodeIgniter gives you the ability to configure a single key that is to be
    517. 

  517. used (almost) every time.</p>
    518. 

  518. <p>It goes without saying that you should guard your key carefully. Should
    519. 

  519. someone gain access to your key, the data will be easily decrypted. If
    520. 

  520. your server is not totally under your control it’s impossible to ensure
    521. 

  521. key security so you may want to think carefully before using it for
    522. 

  522. anything that requires high security, like storing credit card numbers.</p>
    523. 

  523. <p>Your encryption key <strong>must</strong> be as long as the encyption algorithm in use
    524. 

  524. allows. For AES-128, that’s 128 bits or 16 bytes (charcters) long.
    525. 

  525. You will find a table below that shows the supported key lengths of
    526. 

  526. different ciphers.</p>
    527. 

  527. <p>The key should be as random as possible and it <strong>must not</strong> be a regular
    528. 

  528. text string, nor the output of a hashing function, etc. In order to create
    529. 

  529. a proper key, you must use the Encryption library’s <code class="docutils literal"><span class="pre">create_key()</span></code> method</p>
    530. 

  530. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// $key will be assigned a 16-byte (128-bit) random key</span>
    531. 

  531. <span class="nv">$key</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">create_key</span><span class="p">(</span><span class="mi">16</span><span class="p">);</span>
    532. 

  532. </pre></div>
    533. 

  533. </div>
    534. 

  534. <p>The key can be either stored in your <em>application/config/config.php</em>, or
    535. 

  535. you can design your own storage mechanism and pass the key dynamically
    536. 

  536. when encrypting/decrypting.</p>
    537. 

  537. <p>To save your key to your <em>application/config/config.php</em>, open the file
    538. 

  538. and set:</p>
    539. 

  539. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;encryption_key&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;YOUR KEY&#39;</span><span class="p">;</span>
    540. 

  540. </pre></div>
    541. 

  541. </div>
    542. 

  542. <p>You’ll notice that the <code class="docutils literal"><span class="pre">create_key()</span></code> method outputs binary data, which
    543. 

  543. is hard to deal with (i.e. a copy-paste may damage it), so you may use
    544. 

  544. <code class="docutils literal"><span class="pre">bin2hex()</span></code>, <code class="docutils literal"><span class="pre">hex2bin()</span></code> or Base64-encoding to work with the key in
    545. 

  545. a more friendly manner. For example:</p>
    546. 

  546. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Get a hex-encoded representation of the key:</span>
    547. 

  547. <span class="nv">$key</span> <span class="o">=</span> <span class="nb">bin2hex</span><span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">create_key</span><span class="p">(</span><span class="mi">16</span><span class="p">));</span>
    548. 

  548. 

  549. <span class="c1">// Put the same value in your config with hex2bin(),</span>
    550. 

  550. <span class="c1">// so that it is still passed as binary to the library:</span>
    551. 

  551. <span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;encryption_key&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="nb">hex2bin</span><span class="p">(</span><span class="o">&lt;</span><span class="nx">your</span> <span class="nx">hex</span><span class="o">-</span><span class="nx">encoded</span> <span class="nb">key</span><span class="o">&gt;</span><span class="p">);</span>
    552. 

  552. </pre></div>
    553. 

  553. </div>
    554. 

  554. </div>
    555. 

  555. <div class="section" id="supported-encryption-ciphers-and-modes">
    556. 

  556. <span id="ciphers-and-modes"></span><h3><a class="toc-backref" href="#id6">Supported encryption ciphers and modes</a><a class="headerlink" href="#supported-encryption-ciphers-and-modes" title="Permalink to this headline">¶</a></h3>
    557. 

  557. <div class="admonition note">
    558. 

  558. <p class="first admonition-title">Note</p>
    559. 

  559. <p class="last">The terms ‘cipher’ and ‘encryption algorithm’ are interchangeable.</p>
    560. 

  560. </div>
    561. 

  561. <div class="section" id="portable-ciphers">
    562. 

  562. <h4><a class="toc-backref" href="#id7">Portable ciphers</a><a class="headerlink" href="#portable-ciphers" title="Permalink to this headline">¶</a></h4>
    563. 

  563. <p>Because MCrypt and OpenSSL (also called drivers throughout this document)
    564. 

  564. each support different sets of encryption algorithms and often implement
    565. 

  565. them in different ways, our Encryption library is designed to use them in
    566. 

  566. a portable fashion, or in other words - it enables you to use them
    567. 

  567. interchangeably, at least for the ciphers supported by both drivers.</p>
    568. 

  568. <p>It is also implemented in a way that aims to match the standard
    569. 

  569. implementations in other programming languages and libraries.</p>
    570. 

  570. <p>Here’s a list of the so called “portable” ciphers, where
    571. 

  571. “CodeIgniter name” is the string value that you’d have to pass to the
    572. 

  572. Encryption library to use that cipher:</p>
    573. 

  573. <table border="1" class="docutils">
    574. 

  574. <colgroup>
    575. 

  575. <col width="24%" />
    576. 

  576. <col width="18%" />
    577. 

  577. <col width="28%" />
    578. 

  578. <col width="31%" />
    579. 

  579. </colgroup>
    580. 

  580. <thead valign="bottom">
    581. 

  581. <tr class="row-odd"><th class="head">Cipher name</th>
    582. 

  582. <th class="head">CodeIgniter name</th>
    583. 

  583. <th class="head">Key lengths (bits / bytes)</th>
    584. 

  584. <th class="head">Supported modes</th>
    585. 

  585. </tr>
    586. 

  586. </thead>
    587. 

  587. <tbody valign="top">
    588. 

  588. <tr class="row-even"><td>AES-128 / Rijndael-128</td>
    589. 

  589. <td>aes-128</td>
    590. 

  590. <td>128 / 16</td>
    591. 

  591. <td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
    592. 

  592. </tr>
    593. 

  593. <tr class="row-odd"><td>AES-192</td>
    594. 

  594. <td>aes-192</td>
    595. 

  595. <td>192 / 24</td>
    596. 

  596. <td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
    597. 

  597. </tr>
    598. 

  598. <tr class="row-even"><td>AES-256</td>
    599. 

  599. <td>aes-256</td>
    600. 

  600. <td>256 / 32</td>
    601. 

  601. <td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
    602. 

  602. </tr>
    603. 

  603. <tr class="row-odd"><td>DES</td>
    604. 

  604. <td>des</td>
    605. 

  605. <td>56 / 7</td>
    606. 

  606. <td>CBC, CFB, CFB8, OFB, ECB</td>
    607. 

  607. </tr>
    608. 

  608. <tr class="row-even"><td>TripleDES</td>
    609. 

  609. <td>tripledes</td>
    610. 

  610. <td>56 / 7, 112 / 14, 168 / 21</td>
    611. 

  611. <td>CBC, CFB, CFB8, OFB</td>
    612. 

  612. </tr>
    613. 

  613. <tr class="row-odd"><td>Blowfish</td>
    614. 

  614. <td>blowfish</td>
    615. 

  615. <td>128-448 / 16-56</td>
    616. 

  616. <td>CBC, CFB, OFB, ECB</td>
    617. 

  617. </tr>
    618. 

  618. <tr class="row-even"><td>CAST5 / CAST-128</td>
    619. 

  619. <td>cast5</td>
    620. 

  620. <td>88-128 / 11-16</td>
    621. 

  621. <td>CBC, CFB, OFB, ECB</td>
    622. 

  622. </tr>
    623. 

  623. <tr class="row-odd"><td>RC4 / ARCFour</td>
    624. 

  624. <td>rc4</td>
    625. 

  625. <td>40-2048 / 5-256</td>
    626. 

  626. <td>Stream</td>
    627. 

  627. </tr>
    628. 

  628. </tbody>
    629. 

  629. </table>
    630. 

  630. <div class="admonition important">
    631. 

  631. <p class="first admonition-title">Important</p>
    632. 

  632. <p class="last">Because of how MCrypt works, if you fail to provide a key
    633. 

  633. with the appropriate length, you might end up using a different
    634. 

  634. algorithm than the one configured, so be really careful with that!</p>
    635. 

  635. </div>
    636. 

  636. <div class="admonition note">
    637. 

  637. <p class="first admonition-title">Note</p>
    638. 

  638. <p class="last">In case it isn’t clear from the above table, Blowfish, CAST5
    639. 

  639. and RC4 support variable length keys. That is, any number in the
    640. 

  640. shown ranges is valid, although in bit terms that only happens
    641. 

  641. in 8-bit increments.</p>
    642. 

  642. </div>
    643. 

  643. <div class="admonition note">
    644. 

  644. <p class="first admonition-title">Note</p>
    645. 

  645. <p class="last">Even though CAST5 supports key lengths lower than 128 bits
    646. 

  646. (16 bytes), in fact they will just be zero-padded to the
    647. 

  647. maximum length, as specified in <a class="reference external" href="http://tools.ietf.org/rfc/rfc2144.txt">RFC 2144</a>.</p>
    648. 

  648. </div>
    649. 

  649. <div class="admonition note">
    650. 

  650. <p class="first admonition-title">Note</p>
    651. 

  651. <p class="last">Blowfish supports key lengths as small as 32 bits (4 bytes), but
    652. 

  652. our tests have shown that only lengths of 128 bits (16 bytes) or
    653. 

  653. higher are properly supported by both MCrypt and OpenSSL. It is
    654. 

  654. also a bad practice to use such low-length keys anyway.</p>
    655. 

  655. </div>
    656. 

  656. </div>
    657. 

  657. <div class="section" id="driver-specific-ciphers">
    658. 

  658. <h4><a class="toc-backref" href="#id8">Driver-specific ciphers</a><a class="headerlink" href="#driver-specific-ciphers" title="Permalink to this headline">¶</a></h4>
    659. 

  659. <p>As noted above, MCrypt and OpenSSL support different sets of encryption
    660. 

  660. ciphers. For portability reasons and because we haven’t tested them
    661. 

  661. properly, we do not advise you to use the ones that are driver-specific,
    662. 

  662. but regardless, here’s a list of most of them:</p>
    663. 

  663. <table border="1" class="docutils">
    664. 

  664. <colgroup>
    665. 

  665. <col width="15%" />
    666. 

  666. <col width="10%" />
    667. 

  667. <col width="32%" />
    668. 

  668. <col width="44%" />
    669. 

  669. </colgroup>
    670. 

  670. <thead valign="bottom">
    671. 

  671. <tr class="row-odd"><th class="head">Cipher name</th>
    672. 

  672. <th class="head">Driver</th>
    673. 

  673. <th class="head">Key lengths (bits / bytes)</th>
    674. 

  674. <th class="head">Supported modes</th>
    675. 

  675. </tr>
    676. 

  676. </thead>
    677. 

  677. <tbody valign="top">
    678. 

  678. <tr class="row-even"><td>AES-128</td>
    679. 

  679. <td>OpenSSL</td>
    680. 

  680. <td>128 / 16</td>
    681. 

  681. <td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
    682. 

  682. </tr>
    683. 

  683. <tr class="row-odd"><td>AES-192</td>
    684. 

  684. <td>OpenSSL</td>
    685. 

  685. <td>192 / 24</td>
    686. 

  686. <td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
    687. 

  687. </tr>
    688. 

  688. <tr class="row-even"><td>AES-256</td>
    689. 

  689. <td>OpenSSL</td>
    690. 

  690. <td>256 / 32</td>
    691. 

  691. <td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
    692. 

  692. </tr>
    693. 

  693. <tr class="row-odd"><td>Rijndael-128</td>
    694. 

  694. <td>MCrypt</td>
    695. 

  695. <td>128 / 16, 192 / 24, 256 / 32</td>
    696. 

  696. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    697. 

  697. </tr>
    698. 

  698. <tr class="row-even"><td>Rijndael-192</td>
    699. 

  699. <td>MCrypt</td>
    700. 

  700. <td>128 / 16, 192 / 24, 256 / 32</td>
    701. 

  701. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    702. 

  702. </tr>
    703. 

  703. <tr class="row-odd"><td>Rijndael-256</td>
    704. 

  704. <td>MCrypt</td>
    705. 

  705. <td>128 / 16, 192 / 24, 256 / 32</td>
    706. 

  706. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    707. 

  707. </tr>
    708. 

  708. <tr class="row-even"><td>GOST</td>
    709. 

  709. <td>MCrypt</td>
    710. 

  710. <td>256 / 32</td>
    711. 

  711. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    712. 

  712. </tr>
    713. 

  713. <tr class="row-odd"><td>Twofish</td>
    714. 

  714. <td>MCrypt</td>
    715. 

  715. <td>128 / 16, 192 / 24, 256 / 32</td>
    716. 

  716. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    717. 

  717. </tr>
    718. 

  718. <tr class="row-even"><td>CAST-128</td>
    719. 

  719. <td>MCrypt</td>
    720. 

  720. <td>40-128 / 5-16</td>
    721. 

  721. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    722. 

  722. </tr>
    723. 

  723. <tr class="row-odd"><td>CAST-256</td>
    724. 

  724. <td>MCrypt</td>
    725. 

  725. <td>128 / 16, 192 / 24, 256 / 32</td>
    726. 

  726. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    727. 

  727. </tr>
    728. 

  728. <tr class="row-even"><td>Loki97</td>
    729. 

  729. <td>MCrypt</td>
    730. 

  730. <td>128 / 16, 192 / 24, 256 / 32</td>
    731. 

  731. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    732. 

  732. </tr>
    733. 

  733. <tr class="row-odd"><td>SaferPlus</td>
    734. 

  734. <td>MCrypt</td>
    735. 

  735. <td>128 / 16, 192 / 24, 256 / 32</td>
    736. 

  736. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    737. 

  737. </tr>
    738. 

  738. <tr class="row-even"><td>Serpent</td>
    739. 

  739. <td>MCrypt</td>
    740. 

  740. <td>128 / 16, 192 / 24, 256 / 32</td>
    741. 

  741. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    742. 

  742. </tr>
    743. 

  743. <tr class="row-odd"><td>XTEA</td>
    744. 

  744. <td>MCrypt</td>
    745. 

  745. <td>128 / 16</td>
    746. 

  746. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    747. 

  747. </tr>
    748. 

  748. <tr class="row-even"><td>RC2</td>
    749. 

  749. <td>MCrypt</td>
    750. 

  750. <td>8-1024 / 1-128</td>
    751. 

  751. <td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
    752. 

  752. </tr>
    753. 

  753. <tr class="row-odd"><td>RC2</td>
    754. 

  754. <td>OpenSSL</td>
    755. 

  755. <td>8-1024 / 1-128</td>
    756. 

  756. <td>CBC, CFB, OFB, ECB</td>
    757. 

  757. </tr>
    758. 

  758. <tr class="row-even"><td>Camellia-128</td>
    759. 

  759. <td>OpenSSL</td>
    760. 

  760. <td>128 / 16</td>
    761. 

  761. <td>CBC, CFB, CFB8, OFB, ECB</td>
    762. 

  762. </tr>
    763. 

  763. <tr class="row-odd"><td>Camellia-192</td>
    764. 

  764. <td>OpenSSL</td>
    765. 

  765. <td>192 / 24</td>
    766. 

  766. <td>CBC, CFB, CFB8, OFB, ECB</td>
    767. 

  767. </tr>
    768. 

  768. <tr class="row-even"><td>Camellia-256</td>
    769. 

  769. <td>OpenSSL</td>
    770. 

  770. <td>256 / 32</td>
    771. 

  771. <td>CBC, CFB, CFB8, OFB, ECB</td>
    772. 

  772. </tr>
    773. 

  773. <tr class="row-odd"><td>Seed</td>
    774. 

  774. <td>OpenSSL</td>
    775. 

  775. <td>128 / 16</td>
    776. 

  776. <td>CBC, CFB, OFB, ECB</td>
    777. 

  777. </tr>
    778. 

  778. </tbody>
    779. 

  779. </table>
    780. 

  780. <div class="admonition note">
    781. 

  781. <p class="first admonition-title">Note</p>
    782. 

  782. <p class="last">If you wish to use one of those ciphers, you’d have to pass
    783. 

  783. its name in lower-case to the Encryption library.</p>
    784. 

  784. </div>
    785. 

  785. <div class="admonition note">
    786. 

  786. <p class="first admonition-title">Note</p>
    787. 

  787. <p class="last">You’ve probably noticed that all AES cipers (and Rijndael-128)
    788. 

  788. are also listed in the portable ciphers list. This is because
    789. 

  789. drivers support different modes for these ciphers. Also, it is
    790. 

  790. important to note that AES-128 and Rijndael-128 are actually
    791. 

  791. the same cipher, but <strong>only</strong> when used with a 128-bit key.</p>
    792. 

  792. </div>
    793. 

  793. <div class="admonition note">
    794. 

  794. <p class="first admonition-title">Note</p>
    795. 

  795. <p class="last">CAST-128 / CAST-5 is also listed in both the portable and
    796. 

  796. driver-specific ciphers list. This is because OpenSSL’s
    797. 

  797. implementation doesn’t appear to be working correctly with
    798. 

  798. key sizes of 80 bits and lower.</p>
    799. 

  799. </div>
    800. 

  800. <div class="admonition note">
    801. 

  801. <p class="first admonition-title">Note</p>
    802. 

  802. <p class="last">RC2 is listed as supported by both MCrypt and OpenSSL.
    803. 

  803. However, both drivers implement them differently and they
    804. 

  804. are not portable. It is probably worth noting that we only
    805. 

  805. found one obscure source confirming that it is MCrypt that
    806. 

  806. is not properly implementing it.</p>
    807. 

  807. </div>
    808. 

  808. </div>
    809. 

  809. <div class="section" id="encryption-modes">
    810. 

  810. <span id="id1"></span><h4><a class="toc-backref" href="#id9">Encryption modes</a><a class="headerlink" href="#encryption-modes" title="Permalink to this headline">¶</a></h4>
    811. 

  811. <p>Different modes of encryption have different characteristics and serve
    812. 

  812. for different purposes. Some are stronger than others, some are faster
    813. 

  813. and some offer extra features.
    814. 

  814. We are not going in depth into that here, we’ll leave that to the
    815. 

  815. cryptography experts. The table below is to provide brief informational
    816. 

  816. reference to our more experienced users. If you are a beginner, just
    817. 

  817. stick to the CBC mode - it is widely accepted as strong and secure for
    818. 

  818. general purposes.</p>
    819. 

  819. <table border="1" class="docutils">
    820. 

  820. <colgroup>
    821. 

  821. <col width="6%" />
    822. 

  822. <col width="9%" />
    823. 

  823. <col width="9%" />
    824. 

  824. <col width="76%" />
    825. 

  825. </colgroup>
    826. 

  826. <thead valign="bottom">
    827. 

  827. <tr class="row-odd"><th class="head">Mode name</th>
    828. 

  828. <th class="head">CodeIgniter name</th>
    829. 

  829. <th class="head">Driver support</th>
    830. 

  830. <th class="head">Additional info</th>
    831. 

  831. </tr>
    832. 

  832. </thead>
    833. 

  833. <tbody valign="top">
    834. 

  834. <tr class="row-even"><td>CBC</td>
    835. 

  835. <td>cbc</td>
    836. 

  836. <td>MCrypt, OpenSSL</td>
    837. 

  837. <td>A safe default choice</td>
    838. 

  838. </tr>
    839. 

  839. <tr class="row-odd"><td>CTR</td>
    840. 

  840. <td>ctr</td>
    841. 

  841. <td>MCrypt, OpenSSL</td>
    842. 

  842. <td>Considered as theoretically better than CBC, but not as widely available</td>
    843. 

  843. </tr>
    844. 

  844. <tr class="row-even"><td>CFB</td>
    845. 

  845. <td>cfb</td>
    846. 

  846. <td>MCrypt, OpenSSL</td>
    847. 

  847. <td>N/A</td>
    848. 

  848. </tr>
    849. 

  849. <tr class="row-odd"><td>CFB8</td>
    850. 

  850. <td>cfb8</td>
    851. 

  851. <td>MCrypt, OpenSSL</td>
    852. 

  852. <td>Same as CFB, but operates in 8-bit mode (not recommended).</td>
    853. 

  853. </tr>
    854. 

  854. <tr class="row-even"><td>OFB</td>
    855. 

  855. <td>ofb</td>
    856. 

  856. <td>MCrypt, OpenSSL</td>
    857. 

  857. <td>N/A</td>
    858. 

  858. </tr>
    859. 

  859. <tr class="row-odd"><td>OFB8</td>
    860. 

  860. <td>ofb8</td>
    861. 

  861. <td>MCrypt</td>
    862. 

  862. <td>Same as OFB, but operates in 8-bit mode (not recommended).</td>
    863. 

  863. </tr>
    864. 

  864. <tr class="row-even"><td>ECB</td>
    865. 

  865. <td>ecb</td>
    866. 

  866. <td>MCrypt, OpenSSL</td>
    867. 

  867. <td>Ignores IV (not recommended).</td>
    868. 

  868. </tr>
    869. 

  869. <tr class="row-odd"><td>XTS</td>
    870. 

  870. <td>xts</td>
    871. 

  871. <td>OpenSSL</td>
    872. 

  872. <td>Usually used for encrypting random access data such as RAM or hard-disk storage.</td>
    873. 

  873. </tr>
    874. 

  874. <tr class="row-even"><td>Stream</td>
    875. 

  875. <td>stream</td>
    876. 

  876. <td>MCrypt, OpenSSL</td>
    877. 

  877. <td>This is not actually a mode, it just says that a stream cipher is being used. Required because of the general cipher+mode initialization process.</td>
    878. 

  878. </tr>
    879. 

  879. </tbody>
    880. 

  880. </table>
    881. 

  881. </div>
    882. 

  882. </div>
    883. 

  883. <div class="section" id="message-length">
    884. 

  884. <h3><a class="toc-backref" href="#id10">Message Length</a><a class="headerlink" href="#message-length" title="Permalink to this headline">¶</a></h3>
    885. 

  885. <p>It’s probably important for you to know that an encrypted string is usually
    886. 

  886. longer than the original, plain-text string (depending on the cipher).</p>
    887. 

  887. <p>This is influenced by the cipher algorithm itself, the IV prepended to the
    888. 

  888. cipher-text and the HMAC authentication message that is also prepended.
    889. 

  889. Furthermore, the encrypted message is also Base64-encoded so that it is safe
    890. 

  890. for storage and transmission, regardless of a possible character set in use.</p>
    891. 

  891. <p>Keep this information in mind when selecting your data storage mechanism.
    892. 

  892. Cookies, for example, can only hold 4K of information.</p>
    893. 

  893. </div>
    894. 

  894. <div class="section" id="configuring-the-library">
    895. 

  895. <span id="configuration"></span><h3><a class="toc-backref" href="#id11">Configuring the library</a><a class="headerlink" href="#configuring-the-library" title="Permalink to this headline">¶</a></h3>
    896. 

  896. <p>For usability, performance, but also historical reasons tied to our old
    897. 

  897. <a class="reference internal" href="encrypt.html"><span class="doc">Encrypt Class</span></a>, the Encryption library is designed to
    898. 

  898. use repeatedly the same driver, encryption cipher, mode and key.</p>
    899. 

  899. <p>As noted in the “Default behavior” section above, this means using an
    900. 

  900. auto-detected driver (OpenSSL has a higher priority), the AES-128 ciper
    901. 

  901. in CBC mode, and your <code class="docutils literal"><span class="pre">$config['encryption_key']</span></code> value.</p>
    902. 

  902. <p>If you wish to change that however, you need to use the <code class="docutils literal"><span class="pre">initialize()</span></code>
    903. 

  903. method. It accepts an associative array of parameters, all of which are
    904. 

  904. optional:</p>
    905. 

  905. <table border="1" class="docutils">
    906. 

  906. <colgroup>
    907. 

  907. <col width="15%" />
    908. 

  908. <col width="85%" />
    909. 

  909. </colgroup>
    910. 

  910. <thead valign="bottom">
    911. 

  911. <tr class="row-odd"><th class="head">Option</th>
    912. 

  912. <th class="head">Possible values</th>
    913. 

  913. </tr>
    914. 

  914. </thead>
    915. 

  915. <tbody valign="top">
    916. 

  916. <tr class="row-even"><td>driver</td>
    917. 

  917. <td>‘mcrypt’, ‘openssl’</td>
    918. 

  918. </tr>
    919. 

  919. <tr class="row-odd"><td>cipher</td>
    920. 

  920. <td>Cipher name (see <a class="reference internal" href="#ciphers-and-modes"><span class="std std-ref">Supported encryption ciphers and modes</span></a>)</td>
    921. 

  921. </tr>
    922. 

  922. <tr class="row-even"><td>mode</td>
    923. 

  923. <td>Encryption mode (see <a class="reference internal" href="#encryption-modes"><span class="std std-ref">Encryption modes</span></a>)</td>
    924. 

  924. </tr>
    925. 

  925. <tr class="row-odd"><td>key</td>
    926. 

  926. <td>Encryption key</td>
    927. 

  927. </tr>
    928. 

  928. </tbody>
    929. 

  929. </table>
    930. 

  930. <p>For example, if you were to change the encryption algorithm and
    931. 

  931. mode to AES-256 in CTR mode, this is what you should do:</p>
    932. 

  932. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span>
    933. 

  933.         <span class="k">array</span><span class="p">(</span>
    934. 

  934.                 <span class="s1">&#39;cipher&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;aes-256&#39;</span><span class="p">,</span>
    935. 

  935.                 <span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;ctr&#39;</span><span class="p">,</span>
    936. 

  936.                 <span class="s1">&#39;key&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;&lt;a 32-character random string&gt;&#39;</span>
    937. 

  937.         <span class="p">)</span>
    938. 

  938. <span class="p">);</span>
    939. 

  939. </pre></div>
    940. 

  940. </div>
    941. 

  941. <p>Note that we only mentioned that you want to change the ciper and mode,
    942. 

  942. but we also included a key in the example. As previously noted, it is
    943. 

  943. important that you choose a key with a proper size for the used algorithm.</p>
    944. 

  944. <p>There’s also the ability to change the driver, if for some reason you
    945. 

  945. have both, but want to use MCrypt instead of OpenSSL:</p>
    946. 

  946. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Switch to the MCrypt driver</span>
    947. 

  947. <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">&#39;driver&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;mcrypt&#39;</span><span class="p">));</span>
    948. 

  948. 

  949. <span class="c1">// Switch back to the OpenSSL driver</span>
    950. 

  950. <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">&#39;driver&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;openssl&#39;</span><span class="p">));</span>
    951. 

  951. </pre></div>
    952. 

  952. </div>
    953. 

  953. </div>
    954. 

  954. <div class="section" id="encrypting-and-decrypting-data">
    955. 

  955. <h3><a class="toc-backref" href="#id12">Encrypting and decrypting data</a><a class="headerlink" href="#encrypting-and-decrypting-data" title="Permalink to this headline">¶</a></h3>
    956. 

  956. <p>Encrypting and decrypting data with the already configured library
    957. 

  957. settings is simple. As simple as just passing the string to the
    958. 

  958. <code class="docutils literal"><span class="pre">encrypt()</span></code> and/or <code class="docutils literal"><span class="pre">decrypt()</span></code> methods:</p>
    959. 

  959. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$plain_text</span> <span class="o">=</span> <span class="s1">&#39;This is a plain-text message!&#39;</span><span class="p">;</span>
    960. 

  960. <span class="nv">$ciphertext</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">encrypt</span><span class="p">(</span><span class="nv">$plain_text</span><span class="p">);</span>
    961. 

  961. 

  962. <span class="c1">// Outputs: This is a plain-text message!</span>
    963. 

  963. <span class="k">echo</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span><span class="nv">$ciphertext</span><span class="p">);</span>
    964. 

  964. </pre></div>
    965. 

  965. </div>
    966. 

  966. <p>And that’s it! The Encryption library will do everything necessary
    967. 

  967. for the whole process to be cryptographically secure out-of-the-box.
    968. 

  968. You don’t need to worry about it.</p>
    969. 

  969. <div class="admonition important">
    970. 

  970. <p class="first admonition-title">Important</p>
    971. 

  971. <p class="last">Both methods will return FALSE in case of an error.
    972. 

  972. While for <code class="docutils literal"><span class="pre">encrypt()</span></code> this can only mean incorrect
    973. 

  973. configuration, you should always check the return value
    974. 

  974. of <code class="docutils literal"><span class="pre">decrypt()</span></code> in production code.</p>
    975. 

  975. </div>
    976. 

  976. <div class="section" id="how-it-works">
    977. 

  977. <h4><a class="toc-backref" href="#id13">How it works</a><a class="headerlink" href="#how-it-works" title="Permalink to this headline">¶</a></h4>
    978. 

  978. <p>If you must know how the process works, here’s what happens under
    979. 

  979. the hood:</p>
    980. 

  980. <ul class="simple">
    981. 

  981. <li><code class="docutils literal"><span class="pre">$this-&gt;encryption-&gt;encrypt($plain_text)</span></code><ol class="arabic">
    982. 

  982. <li>Derive an encryption key and a HMAC key from your configured
    983. 

  983. <em>encryption_key</em> via HKDF, using the SHA-512 digest algorithm.</li>
    984. 

  984. <li>Generate a random initialization vector (IV).</li>
    985. 

  985. <li>Encrypt the data via AES-128 in CBC mode (or another previously
    986. 

  986. configured cipher and mode), using the above-mentioned derived
    987. 

  987. encryption key and IV.</li>
    988. 

  988. <li>Prepend said IV to the resulting cipher-text.</li>
    989. 

  989. <li>Base64-encode the resulting string, so that it can be safely
    990. 

  990. stored or transferred without worrying about character sets.</li>
    991. 

  991. <li>Create a SHA-512 HMAC authentication message using the derived
    992. 

  992. HMAC key to ensure data integrity and prepend it to the Base64
    993. 

  993. string.</li>
    994. 

  994. </ol>
    995. 

  995. </li>
    996. 

  996. <li><code class="docutils literal"><span class="pre">$this-&gt;encryption-&gt;decrypt($ciphertext)</span></code><ol class="arabic">
    997. 

  997. <li>Derive an encryption key and a HMAC key from your configured
    998. 

  998. <em>encryption_key</em> via HKDF, using the SHA-512 digest algorithm.
    999. 

  999. Because your configured <em>encryption_key</em> is the same, this
    1000. 

  1000. will produce the same result as in the <code class="docutils literal"><span class="pre">encrypt()</span></code> method
    1001. 

  1001. above - otherwise you won’t be able to decrypt it.</li>
    1002. 

  1002. <li>Check if the string is long enough, separate the HMAC out of
    1003. 

  1003. it and validate if it is correct (this is done in a way that
    1004. 

  1004. prevents timing attacks against it). Return FALSE if either of
    1005. 

  1005. the checks fails.</li>
    1006. 

  1006. <li>Base64-decode the string.</li>
    1007. 

  1007. <li>Separate the IV out of the cipher-text and decrypt the said
    1008. 

  1008. cipher-text using that IV and the derived encryption key.</li>
    1009. 

  1009. </ol>
    1010. 

  1010. </li>
    1011. 

  1011. </ul>
    1012. 

  1012. </div>
    1013. 

  1013. <div class="section" id="using-custom-parameters">
    1014. 

  1014. <span id="custom-parameters"></span><h4><a class="toc-backref" href="#id14">Using custom parameters</a><a class="headerlink" href="#using-custom-parameters" title="Permalink to this headline">¶</a></h4>
    1015. 

  1015. <p>Let’s say you have to interact with another system that is out
    1016. 

  1016. of your control and uses another method to encrypt data. A
    1017. 

  1017. method that will most certainly not match the above-described
    1018. 

  1018. sequence and probably not use all of the steps either.</p>
    1019. 

  1019. <p>The Encryption library allows you to change how its encryption
    1020. 

  1020. and decryption processes work, so that you can easily tailor a
    1021. 

  1021. custom solution for such situations.</p>
    1022. 

  1022. <div class="admonition note">
    1023. 

  1023. <p class="first admonition-title">Note</p>
    1024. 

  1024. <p class="last">It is possible to use the library in this way, without
    1025. 

  1025. setting an <em>encryption_key</em> in your configuration file.</p>
    1026. 

  1026. </div>
    1027. 

  1027. <p>All you have to do is to pass an associative array with a few
    1028. 

  1028. parameters to either the <code class="docutils literal"><span class="pre">encrypt()</span></code> or <code class="docutils literal"><span class="pre">decrypt()</span></code> method.
    1029. 

  1029. Here’s an example:</p>
    1030. 

  1030. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Assume that we have $ciphertext, $key and $hmac_key</span>
    1031. 

  1031. <span class="c1">// from on outside source</span>
    1032. 

  1032. 

  1033. <span class="nv">$message</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span>
    1034. 

  1034.         <span class="nv">$ciphertext</span><span class="p">,</span>
    1035. 

  1035.         <span class="k">array</span><span class="p">(</span>
    1036. 

  1036.                 <span class="s1">&#39;cipher&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;blowfish&#39;</span><span class="p">,</span>
    1037. 

  1037.                 <span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;cbc&#39;</span><span class="p">,</span>
    1038. 

  1038.                 <span class="s1">&#39;key&#39;</span> <span class="o">=&gt;</span> <span class="nv">$key</span><span class="p">,</span>
    1039. 

  1039.                 <span class="s1">&#39;hmac_digest&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;sha256&#39;</span><span class="p">,</span>
    1040. 

  1040.                 <span class="s1">&#39;hmac_key&#39;</span> <span class="o">=&gt;</span> <span class="nv">$hmac_key</span>
    1041. 

  1041.         <span class="p">)</span>
    1042. 

  1042. <span class="p">);</span>
    1043. 

  1043. </pre></div>
    1044. 

  1044. </div>
    1045. 

  1045. <p>In the above example, we are decrypting a message that was encrypted
    1046. 

  1046. using the Blowfish cipher in CBC mode and authenticated via a SHA-256
    1047. 

  1047. HMAC.</p>
    1048. 

  1048. <div class="admonition important">
    1049. 

  1049. <p class="first admonition-title">Important</p>
    1050. 

  1050. <p class="last">Note that both ‘key’ and ‘hmac_key’ are used in this
    1051. 

  1051. example. When using custom parameters, encryption and HMAC keys
    1052. 

  1052. are not derived like the default behavior of the library is.</p>
    1053. 

  1053. </div>
    1054. 

  1054. <p>Below is a list of the available options.</p>
    1055. 

  1055. <p>However, unless you really need to and you know what you are doing,
    1056. 

  1056. we advise you to not change the encryption process as this could
    1057. 

  1057. impact security, so please do so with caution.</p>
    1058. 

  1058. <table border="1" class="docutils">
    1059. 

  1059. <colgroup>
    1060. 

  1060. <col width="12%" />
    1061. 

  1061. <col width="14%" />
    1062. 

  1062. <col width="26%" />
    1063. 

  1063. <col width="49%" />
    1064. 

  1064. </colgroup>
    1065. 

  1065. <thead valign="bottom">
    1066. 

  1066. <tr class="row-odd"><th class="head">Option</th>
    1067. 

  1067. <th class="head">Default value</th>
    1068. 

  1068. <th class="head">Mandatory / Optional</th>
    1069. 

  1069. <th class="head">Description</th>
    1070. 

  1070. </tr>
    1071. 

  1071. </thead>
    1072. 

  1072. <tbody valign="top">
    1073. 

  1073. <tr class="row-even"><td>cipher</td>
    1074. 

  1074. <td>N/A</td>
    1075. 

  1075. <td>Yes</td>
    1076. 

  1076. <td>Encryption algorithm (see <a class="reference internal" href="#ciphers-and-modes"><span class="std std-ref">Supported encryption ciphers and modes</span></a>).</td>
    1077. 

  1077. </tr>
    1078. 

  1078. <tr class="row-odd"><td>mode</td>
    1079. 

  1079. <td>N/A</td>
    1080. 

  1080. <td>Yes</td>
    1081. 

  1081. <td>Encryption mode (see <a class="reference internal" href="#encryption-modes"><span class="std std-ref">Encryption modes</span></a>).</td>
    1082. 

  1082. </tr>
    1083. 

  1083. <tr class="row-even"><td>key</td>
    1084. 

  1084. <td>N/A</td>
    1085. 

  1085. <td>Yes</td>
    1086. 

  1086. <td>Encryption key.</td>
    1087. 

  1087. </tr>
    1088. 

  1088. <tr class="row-odd"><td>hmac</td>
    1089. 

  1089. <td>TRUE</td>
    1090. 

  1090. <td>No</td>
    1091. 

  1091. <td>Whether to use a HMAC.
    1092. 

  1092. Boolean. If set to FALSE, then <em>hmac_digest</em> and
    1093. 

  1093. <em>hmac_key</em> will be ignored.</td>
    1094. 

  1094. </tr>
    1095. 

  1095. <tr class="row-even"><td>hmac_digest</td>
    1096. 

  1096. <td>sha512</td>
    1097. 

  1097. <td>No</td>
    1098. 

  1098. <td>HMAC message digest algorithm (see <a class="reference internal" href="#digests"><span class="std std-ref">Supported HMAC authentication algorithms</span></a>).</td>
    1099. 

  1099. </tr>
    1100. 

  1100. <tr class="row-odd"><td>hmac_key</td>
    1101. 

  1101. <td>N/A</td>
    1102. 

  1102. <td>Yes, unless <em>hmac</em> is FALSE</td>
    1103. 

  1103. <td>HMAC key.</td>
    1104. 

  1104. </tr>
    1105. 

  1105. <tr class="row-even"><td>raw_data</td>
    1106. 

  1106. <td>FALSE</td>
    1107. 

  1107. <td>No</td>
    1108. 

  1108. <td>Whether the cipher-text should be raw.
    1109. 

  1109. Boolean. If set to TRUE, then Base64 encoding and
    1110. 

  1110. decoding will not be performed and HMAC will not
    1111. 

  1111. be a hexadecimal string.</td>
    1112. 

  1112. </tr>
    1113. 

  1113. </tbody>
    1114. 

  1114. </table>
    1115. 

  1115. <div class="admonition important">
    1116. 

  1116. <p class="first admonition-title">Important</p>
    1117. 

  1117. <p class="last"><code class="docutils literal"><span class="pre">encrypt()</span></code> and <code class="docutils literal"><span class="pre">decrypt()</span></code> will return FALSE if
    1118. 

  1118. a mandatory parameter is not provided or if a provided
    1119. 

  1119. value is incorrect. This includes <em>hmac_key</em>, unless <em>hmac</em>
    1120. 

  1120. is set to FALSE.</p>
    1121. 

  1121. </div>
    1122. 

  1122. </div>
    1123. 

  1123. <div class="section" id="supported-hmac-authentication-algorithms">
    1124. 

  1124. <span id="digests"></span><h4><a class="toc-backref" href="#id15">Supported HMAC authentication algorithms</a><a class="headerlink" href="#supported-hmac-authentication-algorithms" title="Permalink to this headline">¶</a></h4>
    1125. 

  1125. <p>For HMAC message authentication, the Encryption library supports
    1126. 

  1126. usage of the SHA-2 family of algorithms:</p>
    1127. 

  1127. <table border="1" class="docutils">
    1128. 

  1128. <colgroup>
    1129. 

  1129. <col width="19%" />
    1130. 

  1130. <col width="34%" />
    1131. 

  1131. <col width="47%" />
    1132. 

  1132. </colgroup>
    1133. 

  1133. <thead valign="bottom">
    1134. 

  1134. <tr class="row-odd"><th class="head">Algorithm</th>
    1135. 

  1135. <th class="head">Raw length (bytes)</th>
    1136. 

  1136. <th class="head">Hex-encoded length (bytes)</th>
    1137. 

  1137. </tr>
    1138. 

  1138. </thead>
    1139. 

  1139. <tbody valign="top">
    1140. 

  1140. <tr class="row-even"><td>sha512</td>
    1141. 

  1141. <td>64</td>
    1142. 

  1142. <td>128</td>
    1143. 

  1143. </tr>
    1144. 

  1144. <tr class="row-odd"><td>sha384</td>
    1145. 

  1145. <td>48</td>
    1146. 

  1146. <td>96</td>
    1147. 

  1147. </tr>
    1148. 

  1148. <tr class="row-even"><td>sha256</td>
    1149. 

  1149. <td>32</td>
    1150. 

  1150. <td>64</td>
    1151. 

  1151. </tr>
    1152. 

  1152. <tr class="row-odd"><td>sha224</td>
    1153. 

  1153. <td>28</td>
    1154. 

  1154. <td>56</td>
    1155. 

  1155. </tr>
    1156. 

  1156. </tbody>
    1157. 

  1157. </table>
    1158. 

  1158. <p>The reason for not including other popular algorithms, such as
    1159. 

  1159. MD5 or SHA1 is that they are no longer considered secure enough
    1160. 

  1160. and as such, we don’t want to encourage their usage.
    1161. 

  1161. If you absolutely need to use them, it is easy to do so via PHP’s
    1162. 

  1162. native <a class="reference external" href="http://php.net/manual/en/function.hash-hmac.php">hash_hmac()</a> function.</p>
    1163. 

  1163. <p>Stronger algorithms of course will be added in the future as they
    1164. 

  1164. appear and become widely available.</p>
    1165. 

  1165. </div>
    1166. 

  1166. </div>
    1167. 

  1167. </div>
    1168. 

  1168. <div class="section" id="class-reference">
    1169. 

  1169. <h2><a class="toc-backref" href="#id16">Class Reference</a><a class="headerlink" href="#class-reference" title="Permalink to this headline">¶</a></h2>
    1170. 

  1170. <dl class="class">
    1171. 

  1171. <dt id="CI_Encryption">
    1172. 

  1172. <em class="property">class </em><code class="descname">CI_Encryption</code><a class="headerlink" href="#CI_Encryption" title="Permalink to this definition">¶</a></dt>
    1173. 

  1173. <dd><dl class="method">
    1174. 

  1174. <dt id="CI_Encryption::initialize">
    1175. 

  1175. <code class="descname">initialize</code><span class="sig-paren">(</span><em>$params</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::initialize" title="Permalink to this definition">¶</a></dt>
    1176. 

  1176. <dd><table class="docutils field-list" frame="void" rules="none">
    1177. 

  1177. <col class="field-name" />
    1178. 

  1178. <col class="field-body" />
    1179. 

  1179. <tbody valign="top">
    1180. 

  1180. <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
    1181. 

  1181. <li><strong>$params</strong> (<em>array</em>) – Configuration parameters</li>
    1182. 

  1182. </ul>
    1183. 

  1183. </td>
    1184. 

  1184. </tr>
    1185. 

  1185. <tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">CI_Encryption instance (method chaining)</p>
    1186. 

  1186. </td>
    1187. 

  1187. </tr>
    1188. 

  1188. <tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">CI_Encryption</p>
    1189. 

  1189. </td>
    1190. 

  1190. </tr>
    1191. 

  1191. </tbody>
    1192. 

  1192. </table>
    1193. 

  1193. <p>Initializes (configures) the library to use a different
    1194. 

  1194. driver, cipher, mode or key.</p>
    1195. 

  1195. <p>Example:</p>
    1196. 

  1196. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span>
    1197. 

  1197.         <span class="k">array</span><span class="p">(</span><span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;ctr&#39;</span><span class="p">)</span>
    1198. 

  1198. <span class="p">);</span>
    1199. 

  1199. </pre></div>
    1200. 

  1200. </div>
    1201. 

  1201. <p>Please refer to the <a class="reference internal" href="#configuration"><span class="std std-ref">Configuring the library</span></a> section for detailed info.</p>
    1202. 

  1202. </dd></dl>
    1203. 

  1203. 

  1204. <dl class="method">
    1205. 

  1205. <dt id="CI_Encryption::encrypt">
    1206. 

  1206. <code class="descname">encrypt</code><span class="sig-paren">(</span><em>$data</em><span class="optional">[</span>, <em>$params = NULL</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::encrypt" title="Permalink to this definition">¶</a></dt>
    1207. 

  1207. <dd><table class="docutils field-list" frame="void" rules="none">
    1208. 

  1208. <col class="field-name" />
    1209. 

  1209. <col class="field-body" />
    1210. 

  1210. <tbody valign="top">
    1211. 

  1211. <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
    1212. 

  1212. <li><strong>$data</strong> (<em>string</em>) – Data to encrypt</li>
    1213. 

  1213. <li><strong>$params</strong> (<em>array</em>) – Optional parameters</li>
    1214. 

  1214. </ul>
    1215. 

  1215. </td>
    1216. 

  1216. </tr>
    1217. 

  1217. <tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">Encrypted data or FALSE on failure</p>
    1218. 

  1218. </td>
    1219. 

  1219. </tr>
    1220. 

  1220. <tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
    1221. 

  1221. </td>
    1222. 

  1222. </tr>
    1223. 

  1223. </tbody>
    1224. 

  1224. </table>
    1225. 

  1225. <p>Encrypts the input data and returns its ciphertext.</p>
    1226. 

  1226. <p>Example:</p>
    1227. 

  1227. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$ciphertext</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">encrypt</span><span class="p">(</span><span class="s1">&#39;My secret message&#39;</span><span class="p">);</span>
    1228. 

  1228. </pre></div>
    1229. 

  1229. </div>
    1230. 

  1230. <p>Please refer to the <a class="reference internal" href="#custom-parameters"><span class="std std-ref">Using custom parameters</span></a> section for information
    1231. 

  1231. on the optional parameters.</p>
    1232. 

  1232. </dd></dl>
    1233. 

  1233. 

  1234. <dl class="method">
    1235. 

  1235. <dt id="CI_Encryption::decrypt">
    1236. 

  1236. <code class="descname">decrypt</code><span class="sig-paren">(</span><em>$data</em><span class="optional">[</span>, <em>$params = NULL</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::decrypt" title="Permalink to this definition">¶</a></dt>
    1237. 

  1237. <dd><table class="docutils field-list" frame="void" rules="none">
    1238. 

  1238. <col class="field-name" />
    1239. 

  1239. <col class="field-body" />
    1240. 

  1240. <tbody valign="top">
    1241. 

  1241. <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
    1242. 

  1242. <li><strong>$data</strong> (<em>string</em>) – Data to decrypt</li>
    1243. 

  1243. <li><strong>$params</strong> (<em>array</em>) – Optional parameters</li>
    1244. 

  1244. </ul>
    1245. 

  1245. </td>
    1246. 

  1246. </tr>
    1247. 

  1247. <tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">Decrypted data or FALSE on failure</p>
    1248. 

  1248. </td>
    1249. 

  1249. </tr>
    1250. 

  1250. <tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
    1251. 

  1251. </td>
    1252. 

  1252. </tr>
    1253. 

  1253. </tbody>
    1254. 

  1254. </table>
    1255. 

  1255. <p>Decrypts the input data and returns it in plain-text.</p>
    1256. 

  1256. <p>Example:</p>
    1257. 

  1257. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="k">echo</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span><span class="nv">$ciphertext</span><span class="p">);</span>
    1258. 

  1258. </pre></div>
    1259. 

  1259. </div>
    1260. 

  1260. <p>Please refer to the <a class="reference internal" href="#custom-parameters"><span class="std std-ref">Using custom parameters</span></a> secrion for information
    1261. 

  1261. on the optional parameters.</p>
    1262. 

  1262. </dd></dl>
    1263. 

  1263. 

  1264. <dl class="method">
    1265. 

  1265. <dt id="CI_Encryption::create_key">
    1266. 

  1266. <code class="descname">create_key</code><span class="sig-paren">(</span><em>$length</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::create_key" title="Permalink to this definition">¶</a></dt>
    1267. 

  1267. <dd><table class="docutils field-list" frame="void" rules="none">
    1268. 

  1268. <col class="field-name" />
    1269. 

  1269. <col class="field-body" />
    1270. 

  1270. <tbody valign="top">
    1271. 

  1271. <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
    1272. 

  1272. <li><strong>$length</strong> (<em>int</em>) – Output length</li>
    1273. 

  1273. </ul>
    1274. 

  1274. </td>
    1275. 

  1275. </tr>
    1276. 

  1276. <tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">A pseudo-random cryptographic key with the specified length, or FALSE on failure</p>
    1277. 

  1277. </td>
    1278. 

  1278. </tr>
    1279. 

  1279. <tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
    1280. 

  1280. </td>
    1281. 

  1281. </tr>
    1282. 

  1282. </tbody>
    1283. 

  1283. </table>
    1284. 

  1284. <p>Creates a cryptographic key by fetching random data from
    1285. 

  1285. the operating system’s sources (i.e. /dev/urandom).</p>
    1286. 

  1286. </dd></dl>
    1287. 

  1287. 

  1288. <dl class="method">
    1289. 

  1289. <dt id="CI_Encryption::hkdf">
    1290. 

  1290. <code class="descname">hkdf</code><span class="sig-paren">(</span><em>$key</em><span class="optional">[</span>, <em>$digest = 'sha512'</em><span class="optional">[</span>, <em>$salt = NULL</em><span class="optional">[</span>, <em>$length = NULL</em><span class="optional">[</span>, <em>$info = ''</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::hkdf" title="Permalink to this definition">¶</a></dt>
    1291. 

  1291. <dd><table class="docutils field-list" frame="void" rules="none">
    1292. 

  1292. <col class="field-name" />
    1293. 

  1293. <col class="field-body" />
    1294. 

  1294. <tbody valign="top">
    1295. 

  1295. <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
    1296. 

  1296. <li><strong>$key</strong> (<em>string</em>) – Input key material</li>
    1297. 

  1297. <li><strong>$digest</strong> (<em>string</em>) – A SHA-2 family digest algorithm</li>
    1298. 

  1298. <li><strong>$salt</strong> (<em>string</em>) – Optional salt</li>
    1299. 

  1299. <li><strong>$length</strong> (<em>int</em>) – Optional output length</li>
    1300. 

  1300. <li><strong>$info</strong> (<em>string</em>) – Optional context/application-specific info</li>
    1301. 

  1301. </ul>
    1302. 

  1302. </td>
    1303. 

  1303. </tr>
    1304. 

  1304. <tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">A pseudo-random key or FALSE on failure</p>
    1305. 

  1305. </td>
    1306. 

  1306. </tr>
    1307. 

  1307. <tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
    1308. 

  1308. </td>
    1309. 

  1309. </tr>
    1310. 

  1310. </tbody>
    1311. 

  1311. </table>
    1312. 

  1312. <p>Derives a key from another, presumably weaker key.</p>
    1313. 

  1313. <p>This method is used internally to derive an encryption and HMAC key
    1314. 

  1314. from your configured <em>encryption_key</em>.</p>
    1315. 

  1315. <p>It is publicly available due to its otherwise general purpose. It is
    1316. 

  1316. described in <a class="reference external" href="https://tools.ietf.org/rfc/rfc5869.txt">RFC 5869</a>.</p>
    1317. 

  1317. <p>However, as opposed to the description in RFC 5869, this implementation
    1318. 

  1318. doesn’t support SHA1.</p>
    1319. 

  1319. <p>Example:</p>
    1320. 

  1320. <div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hmac_key</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">hkdf</span><span class="p">(</span>
    1321. 

  1321.         <span class="nv">$key</span><span class="p">,</span>
    1322. 

  1322.         <span class="s1">&#39;sha512&#39;</span><span class="p">,</span>
    1323. 

  1323.         <span class="k">NULL</span><span class="p">,</span>
    1324. 

  1324.         <span class="k">NULL</span><span class="p">,</span>
    1325. 

  1325.         <span class="s1">&#39;authentication&#39;</span>
    1326. 

  1326. <span class="p">);</span>
    1327. 

  1327. 

  1328. <span class="c1">// $hmac_key is a pseudo-random key with a length of 64 bytes</span>
    1329. 

  1329. </pre></div>
    1330. 

  1330. </div>
    1331. 

  1331. </dd></dl>
    1332. 

  1332. 

  1333. </dd></dl>
    1334. 

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