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-################
-Encryption Class
-################
-
-The Encryption Class provides two-way data encryption. It uses a scheme
-that either compiles the message using a randomly hashed bitwise XOR
-encoding scheme, or is 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 be provided with a high
-degree of security appropriate for storage.
-
-Setting your Key
-================
-
-A *key* 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 **only** means to decode data that was
-encrypted with that key, so not only must you choose the key carefully,
-you must never change it if you intend use it for persistent data.
-
-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.
-
-To take maximum advantage of the encryption algorithm, your key should
-be 32 characters in length (256 bits). The key should be as random a
-string as you can concoct, with numbers and uppercase and lowercase
-letters. Your key should **not** be a simple text string. In order to be
-cryptographically secure it needs to be as random as possible.
-
-Your key can be either stored in your **application/config/config.php**, or
-you can design your own storage mechanism and pass the key dynamically
-when encoding/decoding.
-
-To save your key to your **application/config/config.php**, open the file
-and set::
-
- $config['encryption_key'] = "YOUR KEY";
-
-Message Length
-==============
-
-It's important for you to know that the encoded messages the encryption
-function generates will be approximately 2.6 times longer than the
-original message. For example, if you encrypt the string "my super
-secret data", which is 21 characters in length, you'll end up with an
-encoded string that is roughly 55 characters (we say "roughly" because
-the encoded string length increments in 64 bit clusters, so it's not
-exactly linear). Keep this information in mind when selecting your data
-storage mechanism. Cookies, for example, can only hold 4K of
-information.
-
-Initializing the Class
-======================
-
-Like most other classes in CodeIgniter, the Encryption class is
-initialized in your controller using the **$this->load->library** function::
-
- $this->load->library('encrypt');
-
-Once loaded, the Encrypt library object will be available using:
-$this->encrypt
-
-$this->encrypt->encode()
-========================
-
-Performs the data encryption and returns it as a string. Example::
-
- $msg = 'My secret message';
-
- $encrypted_string = $this->encrypt->encode($msg);
-
-
-You can optionally pass your encryption key via the second parameter if
-you don't want to use the one in your config file::
-
- $msg = 'My secret message';
- $key = 'super-secret-key';
-
- $encrypted_string = $this->encrypt->encode($msg, $key);
-
-$this->encrypt->decode()
-========================
-
-Decrypts an encoded string. Example::
-
- $encrypted_string = 'APANtByIGI1BpVXZTJgcsAG8GZl8pdwwa84';
-
- $plaintext_string = $this->encrypt->decode($encrypted_string);
-
-You can optionally pass your encryption key via the second parameter if
-you don't want to use the one in your config file::
-
- $msg = 'My secret message';
- $key = 'super-secret-key';
-
- $encrypted_string = $this->encrypt->decode($msg, $key);
-
-$this->encrypt->set_cipher();
-==============================
-
-Permits you to set an Mcrypt cipher. By default it uses
-**MCRYPT_RIJNDAEL_256**. Example::
-
- $this->encrypt->set_cipher(MCRYPT_BLOWFISH);
-
-Please visit php.net for a list of `available
-ciphers <http://php.net/mcrypt>`_.
-
-If you'd like to manually test whether your server supports Mcrypt you
-can use::
-
- echo ( ! function_exists('mcrypt_encrypt')) ? 'Nope' : 'Yup';
-
-$this->encrypt->set_mode();
-============================
-
-Permits you to set an Mcrypt mode. By default it uses **MCRYPT_MODE_CBC**.
-Example::
-
- $this->encrypt->set_mode(MCRYPT_MODE_CFB);
-
-Please visit php.net for a list of `available
-modes <http://php.net/mcrypt>`_.
-
-$this->encrypt->encode_from_legacy($orig_data, $legacy_mode = MCRYPT_MODE_ECB, $key = '');
-==========================================================================================
-
-Enables you to re-encode data that was originally encrypted with
-CodeIgniter 1.x to be compatible with the Encryption library in
-CodeIgniter 2.x. It is only necessary to use this method if you have
-encrypted data stored permanently such as in a file or database and are
-on a server that supports Mcrypt. "Light" use encryption such as
-encrypted session data or transitory encrypted flashdata require no
-intervention on your part. However, existing encrypted Sessions will be
-destroyed since data encrypted prior to 2.x will not be decoded.
-
-.. important::
- **Why only a method to re-encode the data instead of maintaining legacy
- methods for both encoding and decoding?** The algorithms in the
- Encryption library have improved in CodeIgniter 2.x both for performance
- and security, and we do not wish to encourage continued use of the older
- methods. You can of course extend the Encryption library if you wish and
- replace the new methods with the old and retain seamless compatibility
- with CodeIgniter 1.x encrypted data, but this a decision that a
- developer should make cautiously and deliberately, if at all.
-
-::
-
- $new_data = $this->encrypt->encode_from_legacy($old_encrypted_string);
-
-====================== =============== =======================================================================
-Parameter Default Description
-====================== =============== =======================================================================
-**$orig_data** n/a The original encrypted data from CodeIgniter 1.x's Encryption library
-**$legacy_mode** MCRYPT_MODE_ECB The Mcrypt mode that was used to generate the original encrypted data.
- CodeIgniter 1.x's default was MCRYPT_MODE_ECB, and it will assume that
- to be the case unless overridden by this parameter.
-**$key** n/a The encryption key. This it typically specified in your config file as
- outlined above.
-====================== =============== ======================================================================= \ No newline at end of file