(Node.js) Create ECSDA Signature using Raw r and s Format (not ASN.1)

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Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

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.

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

    var sb = new chilkat.StringBuilder();
    sb.Append("The quick brown fox jumps over the lazy dog");
    var hash = sb.GetHash("sha256","base64","utf-8");

    // Load the ECDSA key to be used for signing.
    var privKey = new chilkat.PrivateKey();
    var success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem");
    if (success !== true) {
        console.log(privKey.LastErrorText);
        return;
    }

    var prng = new chilkat.Prng();
    var ecdsa = new chilkat.Ecc();

    // Produce a signature that is not ASN.1, but is instead the concatenation
    // of the raw r and s signature parts.
    // This feature was added in Chilkat v9.5.0.97
    ecdsa.AsnFormat = false;

    var ecdsaSigBase64 = ecdsa.SignHashENC(hash,"base64",privKey,prng);
    if (ecdsa.LastMethodSuccess !== true) {
        console.log(ecdsa.LastErrorText);
        return;
    }

    console.log("ECDSA signature = " + ecdsaSigBase64);

    // -----------------------------------------------------------
    // Now let's verify the signature using the public key.

    var pubKey = new chilkat.PublicKey();
    success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pubkey.pem");
    if (success !== true) {
        console.log(pubKey.LastErrorText);
        return;
    }

    // Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
    var result = ecdsa.VerifyHashENC(hash,ecdsaSigBase64,"base64",pubKey);
    if (result == 1) {
        console.log("Signature is valid.");
        return;
    }

    if (result == 0) {
        console.log("Signature is invalid.");
        return;
    }

    if (result < 0) {
        console.log(ecdsa.LastErrorText);
        console.log("The VerifyHashENC method call failed.");
        return;
    }


}

chilkatExample();