PHP

DSA R,S Signature Values

See more DSA Examples

Creates a DSA signature. Gets r,s values from the signature. Re-creates the DSA signature ASN.1 from the r,s values. Then verifies the signature using the re-created ASN.1 DSA signature. Chilkat2 PHP

<?php

use Chilkat2\Asn;
use Chilkat2\Crypt2;
use Chilkat2\Dsa;
use Chilkat2\Xml;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

$crypt = new Crypt2();

$crypt->EncodingMode = 'hex';
$crypt->HashAlgorithm = 'sha-1';

$hashStr = $crypt->HashFileENC('qa_data/hamlet.xml');
echo 'hash to sign: ', $hashStr, "\n";

$dsa = new Dsa();

$pemPrivateKey = $dsa->LoadText('qa_data/dsa/dsaPrivKey2.pem');
try {
    $dsa->FromPem($pemPrivateKey);

    // Load the hash to be signed into the DSA object:
    $dsa->SetEncodedHash('hex', $hashStr);

    // Sign the hash.
    $dsa->SignHash();
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Get the ASN.1 signature.
$asnSig = $dsa->GetEncodedSignature('base64');
echo 'Signature: ', $asnSig, "\n";

// Examine the details of the ASN.1 signature.
// We want to get the r,s values as hex strings..
$asn = new Asn();
try {
    $asn->LoadEncoded($asnSig, 'base64');
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Get the ASN.1 as XML.
$xml = new Xml();
$xml->LoadXml($asn->AsnToXml());
echo "Signature as XML: \n";
echo $xml->GetXml(), "\n";

// Sample XML shown here.
// The r and s values are the two hex strings in the XML.

/*
 * <?xml version="1.0" encoding="utf-8"?>
 * <sequence>
 *     <int>2C187F3AB6E47A66497B86CE97BB39E2133810F5</int>
 *     <int>588E53D3F7B69636B48FD7175E99A3961BD7D775</int>
 * </sequence>
 */

// Pretend we're starting with r,s
$r = '2C187F3AB6E47A66497B86CE97BB39E2133810F5';
$s = '588E53D3F7B69636B48FD7175E99A3961BD7D775';

// Build the XML that will be converted to ASN.1
$xml->Clear();
$xml->Tag = 'sequence';
$xml->NewChild2('int', $r);
$xml->NewChild2('int', $s);

// Convert the XML to ASN.1
$asn->LoadAsnXml($xml->GetXml());

// Emit the signature as DER encoded ASN.1 (base64)
$asnSig = $asn->GetEncodedDer('base64');

// --------------------------------------------------------------------
// Verify the signature using the asnSig we built from the r,s values
// --------------------------------------------------------------------

$dsa2 = new Dsa();

// Load the DSA public key to be used for verification:
$pemPublicKey = $dsa2->LoadText('qa_data/dsa/dsaPubKey2.pem');
try {
    $dsa2->FromPublicPem($pemPublicKey);

    // Load the hash to be verified.
    $dsa2->SetEncodedHash('hex', $hashStr);

    // Load the ASN.1 signature:
    $dsa2->SetEncodedSignature('base64', $asnSig);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Verify:
try {
    $dsa2->Verify();
    echo "DSA Signature Verified!\n";
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
}