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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.openssl-decrypt" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>openssl_decrypt</refname>
<refpurpose>Decrypts data</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type class="union"><type>string</type><type>false</type></type><methodname>openssl_decrypt</methodname>
<methodparam><type>string</type><parameter>data</parameter></methodparam>
<methodparam><type>string</type><parameter>cipher_algo</parameter></methodparam>
<methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>passphrase</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>options</parameter><initializer>0</initializer></methodparam>
<methodparam choice="opt"><type>string</type><parameter>iv</parameter><initializer>""</initializer></methodparam>
<methodparam choice="opt"><type class="union"><type>string</type><type>null</type></type><parameter>tag</parameter><initializer>&null;</initializer></methodparam>
<methodparam choice="opt"><type>string</type><parameter>aad</parameter><initializer>""</initializer></methodparam>
</methodsynopsis>
<para>
Takes a raw or base64 encoded string and decrypts it using a given method and passphrase.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
The encrypted message to be decrypted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>cipher_algo</parameter></term>
<listitem>
<para>
The cipher method. For a list of available cipher methods, use
<function>openssl_get_cipher_methods</function>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>passphrase</parameter></term>
<listitem>
<para>
The passphrase. If the passphrase is shorter than expected, it is silently padded with
<literal>NUL</literal> characters; if the passphrase is longer than expected, it is
silently truncated.
</para>
<caution>
<simpara>
There is no key derivation function used for <parameter>passphrase</parameter> as its name
might suggest. The only operation used is padding with <literal>NUL</literal> characters
or truncation if the length is different than expected.
</simpara>
</caution>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>options</parameter></term>
<listitem>
<para>
<parameter>options</parameter> can be one of
<constant>OPENSSL_RAW_DATA</constant>,
<constant>OPENSSL_ZERO_PADDING</constant>
or <constant>OPENSSL_DONT_ZERO_PAD_KEY</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>iv</parameter></term>
<listitem>
<para>
A non-&null; Initialization Vector. If the IV is shorter than expected, it is padded with
<literal>NUL</literal> characters and warning is emitted; if the passphrase is longer
than expected, it is truncated and warning is emitted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>tag</parameter></term>
<listitem>
<para>
The authentication tag in AEAD cipher mode. If it is incorrect, the authentication fails and the function returns &false;.
</para>
<caution>
<simpara>
The length of the <parameter>tag</parameter> is not checked by the function.
It is the caller's responsibility to ensure that the length of the tag
matches the length of the tag retrieved when <function>openssl_encrypt</function>
has been called. Otherwise the decryption may succeed if the given tag only
matches the start of the proper tag.
</simpara>
</caution>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>aad</parameter></term>
<listitem>
<para>
Additional authenticated data.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
The decrypted string on success&return.falseforfailure;.
</para>
</refsect1>
<refsect1 role="errors">
&reftitle.errors;
<para>
Emits an <constant>E_WARNING</constant> level error if an unknown cipher algorithm
is passed via the <parameter>cipher_algo</parameter> parameter.
</para>
<para>
Emits an <constant>E_WARNING</constant> level error if an empty value is passed
in via the <parameter>iv</parameter> parameter.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>8.1.0</entry>
<entry><parameter>tag</parameter> is now nullable.</entry>
</row>
<row>
<entry>7.1.0</entry>
<entry>The <parameter>tag</parameter> and <parameter>aad</parameter> parameters were added.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>openssl_encrypt</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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