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. Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    //  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");
    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();