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| <td><h1>Code Igniter User Guide Version 1.4.0</h1></td> | |
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| Encrypt Class | |
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| <h1>Encrypt Class</h1> | |
| <p>The Encrypt Class provides two-way data encryption. It uses a scheme that pre-compiles | |
| the message using a randomly hashed bitwise XOR encoding scheme, which is then encrypted using | |
| the Mcrypt library. If Mcrypt is not available on your server the encoded message will | |
| still provide a reasonable degree of security for encrypted sessions or other such "light" purposes. | |
| If Mcrypt is available, you'll effectively end up with a double-encrypted message string, which should | |
| provide a very high degree of security.</p> | |
| <h2>Setting your Key</h2> | |
| <p>A <em>key</em> is a piece of information that controls the cryptographic process and permits an encrypted string to be decoded. | |
| In fact, the key you chose will provide the <strong>only</strong> means to decode data that was encrypted with that key, | |
| so not only must you chose the key carefully, you must must never change it if you intend use it for persistent data.</p> | |
| <p>It goes without saying that you should guard your key carefully. | |
| Should someone gain access to your key, the data will be easily decoded. If your server is not totally under your control | |
| it's impossible to ensure key security so you may want to think carefully before using it for anything | |
| that requires high security, like storing credit card numbers.</p> | |
| <p>To take maximum advantage of the encryption algorithm, your key should be 32 characters in length (128 bits). | |
| The key should be as random a string as you can concoct, with numbers and uppercase and lowercase letters. | |
| Your key should <strong>not</strong> be a simple text string. In order to be cryptographically secure it | |
| needs to be as random as possible.</p> | |
| <p>Your key can be either stored in your <dfn>application/config/config.php</dfn>, or you can design your own | |
| storage mechanism and pass the key dynamically when encoding/decoding.</p> | |
| <p>To save your key to your <dfn>application/config/config.php</dfn>, open the file and set:</p> | |
| <code>$config['encryption_key'] = "YOUR KEY";</code> | |
| <h2>Message Length</h2> | |
| <p>It's important for you to know that the encoded messages the encryption function generates will be approximately 2.6 times longer than the original | |
| message. For example, if you encrypt the string "my super secret data", which is 21 characters in length, you'll end up | |
| with an encoded string that is roughly 55 characters (we say "roughly" because the encoded string length increments in | |
| 64 bit clusters, so it's not exactly linear). Keep this information in mind when selecting your data storage mechanism. Cookies, | |
| for example, can only hold 4K of information.</p> | |
| <h2>Initializing the Class</h2> | |
| <p>Like most other classes in Code Igniter, the Encrypt class is initialized in your controller using the <dfn>$this->load->library</dfn> function:</p> | |
| <code>$this->load->library('encrypt');</code> | |
| <p>Once loaded, the Encrypt library object will be available using: <dfn>$this->encrypt</dfn></p> | |
| <h2>$this->encrypt->encode()</h2> | |
| <p>Performs the data encryption and returns it as a string. Example:</p> | |
| <code> | |
| $msg = 'My secret message';<br /> | |
| <br /> | |
| $encrypted_string = $this->encrypt->encode($msg);</code> | |
| <p>You can optionally pass your encryption key via the second parameter if you don't want to use the one in your config file:</p> | |
| <code> | |
| $msg = 'My secret message';<br /> | |
| $key = 'super-secret-key';<br /> | |
| <br /> | |
| $encrypted_string = $this->encrypt->encode($msg, $key);</code> | |
| <h2>$this->encrypt->decode()</h2> | |
| <p>Decrypts an encoded string. Example:</p> | |
| <code> | |
| $encrypted_string = 'APANtByIGI1BpVXZTJgcsAG8GZl8pdwwa84';<br /> | |
| <br /> | |
| $plaintext_string = $this->encrypt->decode($encrypted_string);</code> | |
| <h2>$this->encrypt->set_cypher();</h2> | |
| <p>Permits you to set an Mcrypt cypher. By default it uses <samp>MCRYPT_RIJNDAEL_256</samp>. Example: | |
| <code>$this->encrypt->set_cypher('MCRYPT_BLOWFISH');</code> | |
| <p>Please visit php.net for a list of <a href="http://php.net/mcrypt">available cyphers</a>.</p> | |
| <p>If you'd like to manually test whether your server supports Mcrypt you can use:</p> | |
| <code>echo ( ! function_exists('mcrypt_encrypt')) ? 'Nope' : 'Yup';</code> | |
| <h2>$this->encrypt->set_mode();</h2> | |
| <p>Permits you to set an Mcrypt mode. By default it uses <samp>MCRYPT_MODE_ECB</samp>. Example: | |
| <code>$this->encrypt->set_mode('MCRYPT_MODE_CFB');</code> | |
| <p>Please visit php.net for a list of <a href="http://php.net/mcrypt">available modes</a>.</p> | |
| <h2>$this->encrypt->sha1();</h2> | |
| <p>SHA1 encoding function. Provide a string and it will return a 160 bit one way hash. Note: SHA1, just like MD5 is non-decodable. Example:</p> | |
| <code>$hash = $this->encrypt->sha1('Some string');</code> | |
| <p>Many PHP installations have SHA1 support by default so if all you need is to encode a hash it's simpler to use the native | |
| function:</p> | |
| <code>$hash = sha1('Some string');</code> | |
| <p>If your server does not support SHA1 you can use the provided function.</p> | |
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