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

See more ECC Examples

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.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

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 CkStringBuilder();
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 CkPrivateKey();
success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem");
if (success !== true) {
    console.log(privKey.LastErrorText);
    return;
}

var prng = new CkPrng();
var ecdsa = new CkEcc();

// 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 CkPublicKey();
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;
}