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>mdecrypt_generic</H1
><DIV
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><P
> (PHP 4 >= 4.0.2, PHP 5)</P
>mdecrypt_generic -- Decrypt data</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN116237"
></A
><H2
>Description</H2
>string <B
CLASS="methodname"
>mdecrypt_generic</B
> ( resource td, string data )<BR
></BR
><P
> This function decrypts data. Note that the length of the returned string
can in fact be longer then the unencrypted string, due to the padding of
the data.
</P
><P
> <TABLE
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><DIV
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><P
><B
>例 1. <B
CLASS="function"
>mdecrypt_generic()</B
> example</B
></P
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><code><font color="#000000">
<font color="#0000BB"><?php<br /> </font><font color="#FF8000">/* Data */<br /> </font><font color="#0000BB">$key </font><font color="#007700">= </font><font color="#DD0000">'this is a very long key, even too long for the cipher'</font><font color="#007700">;<br /> </font><font color="#0000BB">$plain_text </font><font color="#007700">= </font><font color="#DD0000">'very important data'</font><font color="#007700">;<br /> <br /> </font><font color="#FF8000">/* Open module, and create IV */ <br /> </font><font color="#0000BB">$td </font><font color="#007700">= </font><font color="#0000BB">mcrypt_module_open</font><font color="#007700">(</font><font color="#DD0000">'des'</font><font color="#007700">, </font><font color="#DD0000">''</font><font color="#007700">, </font><font color="#DD0000">'ecb'</font><font color="#007700">, </font><font color="#DD0000">''</font><font color="#007700">);<br /> </font><font color="#0000BB">$key </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#0000BB">$key</font><font color="#007700">, </font><font color="#0000BB">0</font><font color="#007700">, </font><font color="#0000BB">mcrypt_enc_get_key_size</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">));<br /> </font><font color="#0000BB">$iv_size </font><font color="#007700">= </font><font color="#0000BB">mcrypt_enc_get_iv_size</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">);<br /> </font><font color="#0000BB">$iv </font><font color="#007700">= </font><font color="#0000BB">mcrypt_create_iv</font><font color="#007700">(</font><font color="#0000BB">$iv_size</font><font color="#007700">, </font><font color="#0000BB">MCRYPT_RAND</font><font color="#007700">);<br /><br /> </font><font color="#FF8000">/* Initialize encryption handle */<br /> </font><font color="#007700">if (</font><font color="#0000BB">mcrypt_generic_init</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">, </font><font color="#0000BB">$key</font><font color="#007700">, </font><font color="#0000BB">$iv</font><font color="#007700">) != -</font><font color="#0000BB">1</font><font color="#007700">) {<br /><br /> </font><font color="#FF8000">/* Encrypt data */<br /> </font><font color="#0000BB">$c_t </font><font color="#007700">= </font><font color="#0000BB">mcrypt_generic</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">, </font><font color="#0000BB">$plain_text</font><font color="#007700">);<br /> </font><font color="#0000BB">mcrypt_generic_deinit</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">);<br /><br /> </font><font color="#FF8000">/* Reinitialize buffers for decryption */<br /> </font><font color="#0000BB">mcrypt_generic_init</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">, </font><font color="#0000BB">$key</font><font color="#007700">, </font><font color="#0000BB">$iv</font><font color="#007700">);<br /> </font><font color="#0000BB">$p_t </font><font color="#007700">= </font><font color="#0000BB">mdecrypt_generic</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">, </font><font color="#0000BB">$c_t</font><font color="#007700">);<br /><br /> </font><font color="#FF8000">/* Clean up */<br /> </font><font color="#0000BB">mcrypt_generic_deinit</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">);<br /> </font><font color="#0000BB">mcrypt_module_close</font><font color="#007700">(</font><font color="#0000BB">$td</font><font color="#007700">);<br /> }<br /><br /> if (</font><font color="#0000BB">strncmp</font><font color="#007700">(</font><font color="#0000BB">$p_t</font><font color="#007700">, </font><font color="#0000BB">$plain_text</font><font color="#007700">, </font><font color="#0000BB">strlen</font><font color="#007700">(</font><font color="#0000BB">$plain_text</font><font color="#007700">)) == </font><font color="#0000BB">0</font><font color="#007700">) {<br /> echo </font><font color="#DD0000">"ok\n"</font><font color="#007700">;<br /> } else {<br /> echo </font><font color="#DD0000">"error\n"</font><font color="#007700">;<br /> }<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
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>
</P
><P
> The above example 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
<A
HREF="function.mcrypt-generic-init.html"
><B
CLASS="function"
>mcrypt_generic_init()</B
></A
> before you try to decrypt the
data.
</P
><P
> The decryption handle should always be initialized with
<A
HREF="function.mcrypt-generic-init.html"
><B
CLASS="function"
>mcrypt_generic_init()</B
></A
> with a key and an IV before
calling this function. Where the encryption is done, you should free the
encryption buffers by calling <A
HREF="function.mcrypt-generic-deinit.html"
><B
CLASS="function"
>mcrypt_generic_deinit()</B
></A
>.
See <A
HREF="function.mcrypt-module-open.html"
><B
CLASS="function"
>mcrypt_module_open()</B
></A
> for an example.
</P
><P
> See also <A
HREF="function.mcrypt-generic.html"
><B
CLASS="function"
>mcrypt_generic()</B
></A
>,
<A
HREF="function.mcrypt-generic-init.html"
><B
CLASS="function"
>mcrypt_generic_init()</B
></A
>, and
<A
HREF="function.mcrypt-generic-deinit.html"
><B
CLASS="function"
>mcrypt_generic_deinit()</B
></A
>.
</P
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