   #PHP Manual Mcrypt Encryption Functions mcrypt_generic_init
   mcrypt_get_block_size

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                                mcrypt_generic

   (PHP 4 >= 4.0.2)
   mcrypt_generic -- This function encrypts data

Description

   string mcrypt_generic ( resource td, string data)

   This function encrypts data. The data is padded with "\0" to make sure
   the length of the data is n * blocksize. This function returns the
   encrypted data. Note that the length of the returned string can in
   fact be longer then the input, due to the padding of the data.

   If you want to store the encrypted data in a database make sure to
   store the entire string as returned by mcrypt_generic, or the string
   will not entirely decrypt properly. If your original string is 10
   characters long and the block size is 8 (use
   mcrypt_enc_get_block_size() to determine the blocksize), you would
   need at least 16 characters in your database field. Note the string
   returned by mdecrypt_generic() will be 16 characters as well...use
   rtrim()($str, "\0") to remove the padding.

   If you are for example storing the data in a MySQL database remember
   that varchar fields automatically have trailing spaces removed during
   insertion. As encrypted data can end in a space (ASCII 32), the data
   will be damaged by this removal. Store data in a tinyblob/tinytext (or
   larger) field instead.

   The encryption handle should always be initialized with
   mcrypt_generic_init() with a key and an IV before calling this
   function. Where the encryption is done, you should free the encryption
   buffers by calling mcrypt_generic_deinit(). See mcrypt_module_open()
   for an example.

   See also mdecrypt_generic(), mcrypt_generic_init(), and
   mcrypt_generic_deinit().
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