(PHP ActiveX) ECDSA Sign Data and Get Raw R and S Values

Demonstrates getting the raw R and S value of an ECDSA signature.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows Note: The php_com_dotnet.dll may need to be enabled inside of php.ini.

<?php

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

// To create an ECDSA signature, the data first needs to be hashed.  Then the hash
// is signed.

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Crypt2')
$crypt = new COM("Chilkat.Crypt2");
$crypt->HashAlgorithm = 'SHA256';
$crypt->Charset = 'utf-8';
$crypt->EncodingMode = 'base64';

// Hash a string.
$hash1 = $crypt->hashStringENC('The quick brown fox jumps over the lazy dog');
print 'hash1 = ' . $hash1 . "\n";

// -----------------------------------------------------------
// An ECDSA private key is used for signing.  The public key is for signature verification.
// Load our ECC private key.
// Our private key file contains this:

// 	// -----BEGIN PRIVATE KEY-----
// 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
// 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
// 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
// 	-----END PRIVATE KEY-----

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.PrivateKey')
$privKey = new COM("Chilkat.PrivateKey");
$success = $privKey->LoadPemFile('qa_data/ecc/secp256r1-key-pkcs8.pem');
if ($success != 1) {
    print $privKey->LastErrorText . "\n";
    exit;
}

// Sign the hash..
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Prng')
$prng = new COM("Chilkat.Prng");
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Ecc')
$ecdsa = new COM("Chilkat.Ecc");
$ecdsaSigBase64 = $ecdsa->signHashENC($hash1,'base64',$privKey,$prng);
if ($ecdsa->LastMethodSuccess != 1) {
    print $ecdsa->LastErrorText . "\n";
    exit;
}

// The ECDSA signature is ASN.1 that contains a sequence of 2 large integers (r and s)
// For example:
// SEQUENCE (2 elem)
//   INTEGER (255 bit) 792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9
//   INTEGER (255 bit) 481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5

print 'Base64 ECDSA signature = ' . $ecdsaSigBase64 . "\n";

// If the raw R and S values are needed, here's how to get them:
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Asn')
$asn = new COM("Chilkat.Asn");
$success = $asn->LoadEncoded($ecdsaSigBase64,'base64');
if ($success == 0) {
    print $asn->LastErrorText . "\n";
    exit;
}

// The R and X will be in hexidecimal in the XML.
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Xml')
$xml = new COM("Chilkat.Xml");
$xml->LoadXml($asn->asnToXml());
print $xml->getXml() . "\n";

// The XML looks like this:
// <sequence>
// <int>792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9</int>
// <int>481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5</int>
// </sequence>

// Copy raw R and S hex values into a Chilkat BinData object.
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.BinData')
$bd = new COM("Chilkat.BinData");
$r = $xml->getChildContent('int[0]');
$s = $xml->getChildContent('int[1]');
$bd->AppendEncoded($r,'hex');
$bd->AppendEncoded($s,'hex');

print 'Number of bytes in bd: ' . $bd->NumBytes . "\n";

?>