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mdecrypt_generic

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(PHP 4 >= 4.0.2, PHP 5, PHP 7 < 7.2.0, PECL mcrypt >= 1.0.0)

mdecrypt_generic — Decrypts data

Warning

This function has been DEPRECATED as of PHP 7.1.0. Relying on this function is highly discouraged.

Description

mdecrypt_generic ( resource $td , string $data ) : string

This function decrypts data. Note that the length of the returned string can in fact be longer than the unencrypted string, due to the padding of the data.

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Parameters

td

An encryption descriptor returned by mcrypt_module_open()

data

Encrypted data.

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Examples

Example #1 mdecrypt_generic() Example

<?php
    /* Data */
    $key = 'this is a very long key, even too long for the cipher';
    $plain_text = 'very important data';

    /* Open module, and create IV */
    $td = mcrypt_module_open('des', '', 'ecb', '');
    $key = substr($key, 0, mcrypt_enc_get_key_size($td));
    $iv_size = mcrypt_enc_get_iv_size($td);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);

    /* Initialize encryption handle */
    if (mcrypt_generic_init($td, $key, $iv) != -1) {

        /* Encrypt data */
        $c_t = mcrypt_generic($td, $plain_text);
        mcrypt_generic_deinit($td);

        /* Reinitialize buffers for decryption */
        mcrypt_generic_init($td, $key, $iv);
        $p_t = mdecrypt_generic($td, $c_t);

        /* Clean up */
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);
    }

    if (strncmp($p_t, $plain_text, strlen($plain_text)) == 0) {
        echo "ok\n";
    } else {
        echo "error\n";
    }
?>

The example above shows how to check if the data before the encryption is the same as the data after the decryption. It is very important to reinitialize the encryption buffer with mcrypt_generic_init() before you try to decrypt the data.

The decryption 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.

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See Also

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Document created the 30/01/2003, last modified the 26/10/2018
Source of the printed document:https://www.gaudry.be/en/php-rf-mdecrypt-generic.html

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References

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