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

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

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<?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 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.

$crypt = new CkCrypt2();
$crypt->put_HashAlgorithm('SHA256');
$crypt->put_Charset('utf-8');
$crypt->put_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-----

$privKey = new CkPrivateKey();
$success = $privKey->LoadPemFile('qa_data/ecc/secp256r1-key-pkcs8.pem');
if ($success != true) {
    print $privKey->lastErrorText() . "\n";
    exit;
}

// Sign the hash..
$prng = new CkPrng();
$ecdsa = new CkEcc();
$ecdsaSigBase64 = $ecdsa->signHashENC($hash1,'base64',$privKey,$prng);
if ($ecdsa->get_LastMethodSuccess() != true) {
    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:
$asn = new CkAsn();
$success = $asn->LoadEncoded($ecdsaSigBase64,'base64');
if ($success == false) {
    print $asn->lastErrorText() . "\n";
    exit;
}

// The R and X will be in hexidecimal in the XML.
$xml = new CkXml();
$xml->LoadXml($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.
$bd = new CkBinData();
$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->get_NumBytes() . "\n";

?>