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

<?xml version="1.0" encoding="iso-8859-1"?>
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  <refentry id="function.openssl-verify">
   <refnamediv>
    <refname>openssl_verify</refname>
    <refpurpose>Verify signature</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>openssl_verify</methodname>
      <methodparam><type>string</type><parameter>data</parameter></methodparam>
      <methodparam><type>string</type><parameter>signature</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>pub_key_id</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>signature_alg</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns 1 if the signature is correct, 0 if it is incorrect, and
     -1 on error.
    </para>
    <para>
     <function>openssl_verify</function> verifies that the
     <parameter>signature</parameter> is correct for the specified
     <parameter>data</parameter> using the public key associated with
     <parameter>pub_key_id</parameter>. This must be the public key
     corresponding to the private key used for signing.
    </para>
    <note>
     <para>
      Optional 4th parameter <parameter>signature_alg</parameter> was added in
      version 5.2.0. Its default value is
      <constant>OPENSSL_ALGO_SHA1</constant>. For more information see the
      list of <link linkend="openssl.signature-algos">Signature Algorithms</link>.
     </para>
    </note>
    <para>
     <example>
      <title><function>openssl_verify</function> example</title>
      <programlisting role="php">
<![CDATA[
<?php
// $data and $signature are assumed to contain the data and the signature

// fetch public key from certificate and ready it
$fp = fopen("/src/openssl-0.9.6/demos/sign/cert.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);
$pubkeyid = openssl_get_publickey($cert);

// state whether signature is okay or not
$ok = openssl_verify($data, $signature, $pubkeyid);
if ($ok == 1) {
    echo "good";
} elseif ($ok == 0) {
    echo "bad";
} else {
    echo "ugly, error checking signature";
}
// free the key from memory
openssl_free_key($pubkeyid);
?>
]]>
      </programlisting>
     </example>
    </para>
    <simpara>
     See also <function>openssl_sign</function>.
    </simpara>
   </refsect1>
  </refentry>

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