(Node.js) 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.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

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

    var crypt = new chilkat.Crypt2();

    crypt.EncodingMode = "hex";
    crypt.HashAlgorithm = "sha-1";

    var hashStr = crypt.HashFileENC("qa_data/hamlet.xml");
    console.log("hash to sign: " + hashStr);

    var dsa = new chilkat.Dsa();

    var pemPrivateKey;
    pemPrivateKey = dsa.LoadText("qa_data/dsa/dsaPrivKey2.pem");
    var success = dsa.FromPem(pemPrivateKey);
    if (success == false) {
        console.log(dsa.LastErrorText);
        return;
    }

    // Load the hash to be signed into the DSA object:
    success = dsa.SetEncodedHash("hex",hashStr);
    if (success == false) {
        console.log(dsa.LastErrorText);
        return;
    }

    // Sign the hash.
    success = dsa.SignHash();
    if (success == false) {
        console.log(dsa.LastErrorText);
        return;
    }

    // Get the ASN.1 signature.
    var asnSig = dsa.GetEncodedSignature("base64");
    console.log("Signature: " + asnSig);

    // Examine the details of the ASN.1 signature.
    // We want to get the r,s values as hex strings..
    var asn = new chilkat.Asn();
    success = asn.LoadEncoded(asnSig,"base64");
    if (success == false) {
        console.log(asn.LastErrorText);
        return;
    }

    // Get the ASN.1 as XML.
    var xml = new chilkat.Xml();
    success = xml.LoadXml(asn.AsnToXml());
    console.log("Signature as XML: ");
    console.log(xml.GetXml());

    // 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
    var r = "2C187F3AB6E47A66497B86CE97BB39E2133810F5";
    var 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
    success = 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
    // --------------------------------------------------------------------

    var dsa2 = new chilkat.Dsa();

    // Load the DSA public key to be used for verification:
    var pemPublicKey;
    pemPublicKey = dsa2.LoadText("qa_data/dsa/dsaPubKey2.pem");
    success = dsa2.FromPublicPem(pemPublicKey);
    if (success == false) {
        console.log(dsa2.LastErrorText);
        return;
    }

    // Load the hash to be verified.
    success = dsa2.SetEncodedHash("hex",hashStr);
    if (success == false) {
        console.log(dsa2.LastErrorText);
        return;
    }

    // Load the ASN.1 signature:
    success = dsa2.SetEncodedSignature("base64",asnSig);
    if (success == false) {
        console.log(dsa2.LastErrorText);
        return;
    }

    // Verify:
    success = dsa2.Verify();
    if (success == false) {
        console.log(dsa2.LastErrorText);
    }
    else {
        console.log("DSA Signature Verified!");
    }


}

chilkatExample();