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PHP Cookbook by Adam Trachtenberg, David Sklar

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14.7. Encrypting and Decrypting Data

Problem

You want to encrypt and decrypt data using one of a variety of popular algorithms.

Solution

Use PHP’s mcrypt extension:

$key  = 'That golden key that opes the palace of eternity.';
$data = 'The chicken escapes at dawn. Send help with Mr. Blue.';
$alg  = MCRYPT_BLOWFISH;
$mode = MCRYPT_MODE_CBC;

$iv = mcrypt_create_iv(mcrypt_get_iv_size($alg,$mode),MCRYPT_DEV_URANDOM);
$encrypted_data = mcrypt_encrypt($alg, $key, $data, $mode, $iv);
$plain_text = base64_encode($encrypted_data);

print $plain_text."\n";
$decoded = mcrypt_decrypt($alg,$key,base64_decode($plain_text),$mode,$iv);
print $decoded."\n";
NNB9WnuCYjyd3Y7vUh7XDfWFCWnQY0BsMehHNmBHbGOdJ3cM+yghABb/XyrJ+w3xz9tms74/a70=
               The chicken escapes at dawn. Send help with Mr. Blue.

Discussion

The mcrypt extension is an interface with mcrypt, a library that implements many different encryption algorithms. The data is encrypted and decrypted by mcrypt_encrypt( ) and mcrypt_decrypt( ), respectively. They each take five arguments. The first is the algorithm to use. To find which algorithms mcrypt supports on your system, call mcrypt_list_algorithms( ) . The full list of mcrypt algorithms is shown in Table 14-1. The second argument is the encryption key; the third argument is the data to encrypt or decrypt. The fourth argument is the mode for the encryption or decryption (a list of supported modes is returned by mcrypt_list_modes( ) ). The fifth argument is an initialization vector (IV), used by ...

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