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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.sodium-crypto-secretstream-xchacha20poly1305-init-pull" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>sodium_crypto_secretstream_xchacha20poly1305_init_pull</refname>
<refpurpose>Initialize a secretstream context for decryption</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>string</type><methodname>sodium_crypto_secretstream_xchacha20poly1305_init_pull</methodname>
<methodparam><type>string</type><parameter>header</parameter></methodparam>
<methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>key</parameter></methodparam>
</methodsynopsis>
<para>
Initialize a secretstream context for decryption.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<variablelist>
<varlistentry>
<term><parameter>header</parameter></term>
<listitem>
<para>
The header of the secretstream. This should be one of the values produced by
<function>sodium_crypto_secretstream_xchacha20poly1305_init_push</function>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>key</parameter></term>
<listitem>
<para>
Encryption key (256-bit).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Secretstream state.
</para>
</refsect1>
<refsect1 role="examples"><!-- {{{ -->
&reftitle.examples;
<example xml:id="sodium-crypto-secretstream-xchacha20poly1305-init-pull.example.basic"><!-- {{{ -->
<title><function>sodium_crypto_secretstream_xchacha20poly1305_init_pull</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
function decrypt_file(string $inputFilePath, string $outputFilePath, string $key): void
{
$inputFile = fopen($inputFilePath, 'rb');
$outputFile = fopen($outputFilePath, 'wb');
$header = fread($inputFile, 24);
$state = sodium_crypto_secretstream_xchacha20poly1305_init_pull($header, $key);
$inputFileSize = fstat($inputFile)['size'];
// Decrypt the file and write its contents to the output file:
for ($i = 24; $i < $inputFileSize; $i += 8192) {
$ctxt_chunk = fread($inputFile, 8192);
// We're not using $tag, but in real protocols you can use this on encrypt to e.g.
// trigger a re-key or indicate the end of file. Then, on decrypt, you can assert
// this behavior.
[$ptxt_chunk, $tag] = sodium_crypto_secretstream_xchacha20poly1305_pull($state, $ctxt_chunk);
fwrite($outputFile, $ptxt_chunk);
}
sodium_memzero($state);
fclose($inputFile);
fclose($outputFile);
}
// sodium_crypto_secretstream_xchacha20poly1305_keygen()
$key = sodium_base642bin('MS0lzb7HC+thY6jY01pkTE/cwsQxnRq0/2L1eL4Hxn8=', SODIUM_BASE64_VARIANT_ORIGINAL);
$example = sodium_hex2bin('971e33b255f0990ef3931caf761c59136efa77b434832f28ec719e3ff73f5aec38b3bba1574ab5b70a8844d8da36a668e802cfea2c');
file_put_contents('hello.enc', $example);
decrypt_file('hello.enc', 'hello.txt.decrypted', $key);
var_dump(file_get_contents('hello.txt.decrypted'));
?>
]]>
</programlisting>
&example.outputs.similar;
<screen>
<![CDATA[
string(12) "Hello world!"
]]>
</screen>
</example><!-- }}} -->
</refsect1><!-- }}} -->
</refentry>
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sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
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sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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-->
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