For decrypting content which was previously encrypted with Mcrypt you need to have the options with which the encryption has been called.

There is one emminent difference for you. When you did not provide a vector at encryption you need to get it after you encrypted the content by using the getVector() method on the encryption filter. Without the correct vector you will not be able to decrypt the content.

As soon as you have provided all options decryption is as simple as encryption.

// Use the default blowfish settings
$filter = new Zend_Filter_Decrypt('myencryptionkey');

// Set the vector with which the content was encrypted
$filter->setVector('myvector');

$decrypted = $filter->filter('encoded_text_normally_unreadable');
print $decrypted;

        

Note: Note that you will get an exception if the mcrypt extension is not available in your environment.

Note: You should also note that all settings which be checked when you create the instance or when you call setEncryption(). If mcrypt detects problem with your settings an exception will be thrown.

Decryption with OpenSSL is as simple as encryption. But you need to have all data from the person who encrypted the content.

For decryption with OpenSSL you need:

• private: Your private key which will be used for decrypting the content. The private key can be eighter a filename with path of the key file, or just the content of the key file itself.

• envelope: The encrypted envelope key from the user who encrypted the content. You can eigther provide the path and filename of the key file, or just the content of the key file itself.

// Use openssl and provide a private key
$filter = new Zend_Filter_Decrypt(array('adapter' => 'openssl', 'private' => '/path/to/mykey/private.pem');

// of course you can also give the envelope keys at initiation
$filter->setEnvelopeKey(array('/key/from/encoder/first.pem', '/key/from/encoder/second.pem');

        

Note: Note that the OpenSSL adapter will not work when you do not provide valid keys.

Optionally it could be necessary to provide the passphrase for decrypting the keys themself by using the setPassphrase() method.

// Use openssl and provide a private key
$filter = new Zend_Filter_Decrypt(array('adapter' => 'openssl', 'private' => '/path/to/mykey/private.pem');

// of course you can also give the envelope keys at initiation
$filter->setEnvelopeKey(array('/key/from/encoder/first.pem', '/key/from/encoder/second.pem');
       ->setPassphrase('mypassphrase');

        

At last, decode the content. Our complete example for decrypting the previously encrypted content looks like this.

// Use openssl and provide a private key
$filter = new Zend_Filter_Decrypt(array('adapter' => 'openssl', 'private' => '/path/to/mykey/private.pem');

// of course you can also give the envelope keys at initiation
$filter->setEnvelopeKey(array('/key/from/encoder/first.pem', '/key/from/encoder/second.pem');
       ->setPassphrase('mypassphrase');

$decrypted = $filter->filter('encoded_text_normally_unreadable');
print $decrypted;

        

When you have installed the Mcrypt extension you can use the Mcrypt adapter. This adapter supports the following options at initiation:

• key: The encryption key with which the input will be encrypted. You need the same key for decryption.

• algorithm: The algorithm which has to be used. It should be one of the algorithm ciphers which can be found under » PHP's mcrypt ciphers. If not set it defaults to blowfish.

• algorithm_directory: The directory where the algorithm can be found. If not set it defaults to the path set within the mcrypt extension.

• mode: The encryption mode which has to be used. It should be one of the modes which can be found under » PHP's mcrypt modes. If not set it defaults to cbc.

• mode_directory: The directory where the mode can be found. If not set it defaults to the path set within the mcrypt extension.

• vector: The initialization vector which shall be used. If not set it will be a random vector.

If you give a string instead of an array, this string will be used as key.

You can get/set the encryption values also afterwards with the getEncryption() and setEncryption() methods.

Note: Note that you will get an exception if the mcrypt extension is not available in your environment.

Note: You should also note that all settings which be checked when you create the instance or when you call setEncryption(). If mcrypt detects problem with your settings an exception will be thrown.

You can get/set the encryption vector by calling getVector() and setVector(). A given string will be truncated or padded to the needed vector size of the used algorithm.

Note: Note that when you are not using an own vector, you must get the vector and store it. Otherwise you will not be able to decode the encoded string.

// Use the default blowfish settings
$filter = new Zend_Filter_Encrypt('myencryptionkey');

// Set a own vector, otherwise you must call getVector()
// and store this vector for later decryption
$filter->setVector('myvector');
// $filter->getVector();

$encrypted = $filter->filter('text_to_be_encoded');
print $encrypted;

// For decryption look at the Decrypt filter

        

When you have installed the OpenSSL extension you can use the OpenSSL adapter. This adapter supports the following options at initiation:

• public: The public key of the user whom you want to provide the encrpted content. You can give multiple public keys by using an array. You can eigther provide the path and filename of the key file, or just the content of the key file itself.

• private: Your private key which will be used for encrypting the content. Also the private key can be eighter a filename with path of the key file, or just the content of the key file itself.

You can get/set the public keys also afterwards with the getPublicKey() and setPublicKey() methods. The private key can also be get and set with the related getPrivateKey() and setPrivateKey() methods.

// Use openssl and provide a private key
$filter = new Zend_Filter_Encrypt(array('adapter' => 'openssl', 'private' => '/path/to/mykey/private.pem');

// of course you can also give the public keys at initiation
$filter->setPublicKey(array('/public/key/path/first.pem', '/public/key/path/second.pem');

        

Note: Note that the OpenSSL adapter will not work when you do not provide valid keys.

When you want to encode also the keys, then you have to provide a passphrase with the setPassphrase() method. When you want to decode content which was encoded with a passphrase you will not only need the public key, but also the passphrase to decode the encrypted key.

// Use openssl and provide a private key
$filter = new Zend_Filter_Encrypt(array('adapter' => 'openssl', 'private' => '/path/to/mykey/private.pem');

// of course you can also give the public keys at initiation
$filter->setPublicKey(array('/public/key/path/first.pem', '/public/key/path/second.pem')
       ->setPassphrase('mypassphrase');

        

At last, when you use OpenSSL you need to give the receiver the encrypted content, the passphrase when have provided one, and the envelope keys for decryption.

This means for you, that you have to get the envelope keys after the encryption with the getEnvelopeKey() method.

So our complete example for encrypting content with OpenSSL look like this.

// Use openssl and provide a private key
$filter = new Zend_Filter_Encrypt(array('adapter' => 'openssl', 'private' => '/path/to/mykey/private.pem');

// of course you can also give the public keys at initiation
$filter->setPublicKey(array('/public/key/path/first.pem', '/public/key/path/second.pem')
       ->setPassphrase('mypassphrase');

$encrypted = $filter->filter('text_to_be_encoded');
$envelope  = $filter->getEnvelopeKey();
print $encrypted;

// For decryption look at the Decrypt filter