php-doc-en/reference/openssl/functions/openssl-sign.xml

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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.openssl-sign">
 <refnamediv>
  <refname>openssl_sign</refname>
  <refpurpose>Generate signature</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>openssl_sign</methodname>
   <methodparam><type>string</type><parameter>data</parameter></methodparam>
   <methodparam><type>string</type><parameter role="reference">signature</parameter></methodparam>
   <methodparam><type>mixed</type><parameter>priv_key_id</parameter></methodparam>
   <methodparam choice="opt"><type>mixed</type><parameter>signature_alg</parameter><initializer>OPENSSL_ALGO_SHA1</initializer></methodparam>
  </methodsynopsis>
  <para>
   <function>openssl_sign</function> computes a signature for the
   specified <parameter>data</parameter> by generating a cryptographic
   digital signature using the private key associated with
   <parameter>priv_key_id</parameter>. Note that the data itself is
   not encrypted.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>data</parameter></term>
     <listitem>
      <para>
       The string of data you wish to sign
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>signature</parameter></term>
     <listitem>
      <para>
       If the call was successful the signature is returned in
       <parameter>signature</parameter>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>priv_key_id</parameter></term>
     <listitem>
      <para>
       <type>resource</type> - a key, returned by <function>openssl_get_privatekey</function>
      </para>
      <para>
       <type>string</type> - a PEM formatted key
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>signature_alg</parameter></term>
     <listitem>
      <para>
       <type>int</type> - one of these <link linkend="openssl.signature-algos">Signature Algorithms</link>.
      </para>
      <para>
       <type>string</type> - a valid string returned by <function>openssl_get_md_methods</function> example, "sha256WithRSAEncryption" or "sha384".
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>openssl_sign</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// $data is assumed to contain the data to be signed

// fetch private key from file and ready it
$pkeyid = openssl_pkey_get_private("file://src/openssl-0.9.6/demos/sign/key.pem");

// compute signature
openssl_sign($data, $signature, $pkeyid);

// free the key from memory
openssl_free_key($pkeyid);
?>
]]>
    </programlisting>
   </example>
   <example>
    <title><function>openssl_sign</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
//data you want to sign
$data = 'my data';

//create new private and public key
$new_key_pair = openssl_pkey_new(array(
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
));
openssl_pkey_export($new_key_pair, $private_key_pem);

$details = openssl_pkey_get_details($new_key_pair);
$public_key_pem = $details['key'];

//create signature
openssl_sign($data, $signature, $private_key_pem, OPENSSL_ALGO_SHA256);

//save for later
file_put_contents('private_key.pem', $private_key_pem);
file_put_contents('public_key.pem', $public_key_pem);
file_put_contents('signature.dat', $signature);

//verify signature
$r = openssl_verify($data, $signature, $public_key_pem, "sha256WithRSAEncryption");
var_dump($r);
?>
]]>
    </programlisting>
   </example>
 
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>openssl_verify</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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