Node.js

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

See more ECC Examples

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.

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.

    //  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();
    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();