(PHP Extension) ECDSA Sign and Verify

Demonstrates how to create an ECDSA signature on the SHA256 hash of some data, and then verify.

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

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

// First load an ECDSA private key to be used for signing.
$privKey = new CkPrivateKey();
$success = $privKey->LoadEncryptedPemFile('qa_data/ecc/secp256r1-key-pkcs8-secret.pem','secret');
if ($success == false) {
    print $privKey->lastErrorText() . "\n";
    exit;
}

// Sign the SHA256 hash of some data.
$bd = new CkBinData();
$success = $bd->LoadFile('qa_data/hamlet.xml');
if ($success == false) {
    print 'Failed to load file to be hashed.' . "\n";
    exit;
}

$crypt = new CkCrypt2();
$crypt->put_HashAlgorithm('sha256');
$crypt->put_EncodingMode('base64');
$hashStr = $crypt->hashBdENC($bd);

$ecdsa = new CkEcc();
$prng = new CkPrng();
// Returns ASN.1 signature as a base64 string.
$sig = $ecdsa->signHashENC($hashStr,'base64',$privKey,$prng);
print 'sig = ' . $sig . "\n";

// The signature is in ASN.1 format (which may be described as the "encoded DSS signature").
// SEQUENCE (2 elem)
//   INTEGER (255 bit) 4849395540832462044300553275435608522154141569743642905628579547100940...
//   INTEGER (255 bit) 3680701124244788134409868118208591399799457104230118295614152238560005...

// If you wish, you can get the r and s components of the signature like this:
$asn = new CkAsn();
$asn->LoadEncoded($sig,'base64');
$xml = new CkXml();
$xml->LoadXml($asn->asnToXml());

print $xml->getXml() . "\n";

// We now have this:
// <?xml version="1.0" encoding="utf-8"?>
// <sequence>
//     <int>6650D422D86BA4A228B5617604E59052591B9B2C32EF324C44D09EF67E5F0060</int>
//     <int>0CFD9F6AC85042FC70F672C141BA6B2A4CAFBB906C3D907BCCC1BED62B28326F</int>
// </sequence>

// Get the "r" and "s" as hex strings
$r = $xml->getChildContentByIndex(0);
$s = $xml->getChildContentByIndex(1);

print 'r = ' . $r . "\n";
print 's = ' . $s . "\n";

// --------------------------------------------------------------------
// Now verify against the hash of the original data.

// Get the corresponding public key.
$pubKey = new CkPublicKey();
$success = $pubKey->LoadFromFile('qa_data/ecc/secp256r1-pub.pem');
if ($success == false) {
    print $pubKey->lastErrorText() . "\n";
    exit;
}

// We already have the SHA256 hash of the original data (hashStr) so no need to re-do it..
$ecc2 = new CkEcc();
$result = $ecc2->VerifyHashENC($hashStr,$sig,'base64',$pubKey);
if ($result != 1) {
    print $ecc2->lastErrorText() . "\n";
    exit;
}

print 'Verified!' . "\n";

// Note: If we have only r,s and wish to reconstruct the ASN.1 signature, we do it like this:
$xml2 = new CkXml();
$xml2->put_Tag('sequence');
$xml2->NewChild2('int',$r);
$xml2->NewChild2('int',$s);

$asn2 = new CkAsn();
$asn2->LoadAsnXml($xml2->getXml());
$encodedSig = $asn2->getEncodedDer('base64');
print 'encoded DSS signature: ' . $encodedSig . "\n";

// You can go to https://lapo.it/asn1js/  and copy/paste the base64 encodedSig into the online tool, then press the "decode" button.
// You will see the ASN.1 such as this:

// SEQUENCE (2 elem)
//   INTEGER (255 bit) 4849395540832462044300553275435608522154141569743642905628579547100940...
//   INTEGER (255 bit) 3680701124244788134409868118208591399799457104230118295614152238560005...

?>