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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.mcrypt-get-iv-size" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>mcrypt_get_iv_size</refname>
<refpurpose>Returns the size of the IV belonging to a specific cipher/mode combination</refpurpose>
</refnamediv>
<refsynopsisdiv>
&warn.deprecated.function-7-1-0.removed-7-2-0;
</refsynopsisdiv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>int</type><methodname>mcrypt_get_iv_size</methodname>
<methodparam><type>string</type><parameter>cipher</parameter></methodparam>
<methodparam><type>string</type><parameter>mode</parameter></methodparam>
</methodsynopsis>
<para>
Gets the size of the IV belonging to a specific
<parameter>cipher</parameter>/<parameter>mode</parameter> combination.
</para>
<para>
It is more useful to use the <function>mcrypt_enc_get_iv_size</function>
function as this uses the resource returned by
<function>mcrypt_module_open</function>.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>cipher</parameter></term>
<listitem>
&mcrypt.parameter.cipher;
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
&mcrypt.parameter.mode;
<para>
The IV is ignored in ECB mode as this mode does not require it. You will
need to have the same IV (think: starting point) both at encryption and
decryption stages, otherwise your encryption will fail.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns the size of the Initialization Vector (IV) in bytes. On error the
function returns &false;. If the IV is ignored in the specified cipher/mode
combination zero is returned.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>mcrypt_get_iv_size</function> Example</title>
<programlisting role="php">
<![CDATA[
<?php
echo mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB) . "\n";
echo mcrypt_get_iv_size('des', 'ecb') . "\n";
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>mcrypt_get_block_size</function></member>
<member><function>mcrypt_enc_get_iv_size</function></member>
<member><function>mcrypt_create_iv</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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