(JavaScript) Create a JWS Using ECDSA P-256 SHA-256

Creates and validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

Note: This example requires Chilkat v11.0.0 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 requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Note: This example requires Chilkat v9.5.0.66 or greater.

// Use the following ECC key loaded from JWK format.
var sbJwk = new CkStringBuilder();
sbJwk.Append("{\"kty\":\"EC\",");
sbJwk.Append("\"crv\":\"P-256\",");
sbJwk.Append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",");
sbJwk.Append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\",");
sbJwk.Append("\"d\":\"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI\"");
sbJwk.Append("}");

var eccKey = new CkPrivateKey();
// Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
// into the private key object. (See the online reference documentation..)
success = eccKey.LoadJwk(sbJwk.GetAsString());
if (success == false) {
    console.log(eccKey.LastErrorText);
    return;
}

// Create the JWS Protected Header
var jwsProtHdr = new CkJsonObject();
jwsProtHdr.AppendString("alg","ES256");

var jws = new CkJws();

// Set the protected header:
var signatureIndex = 0;
jws.SetProtectedHeader(signatureIndex,jwsProtHdr);

// Set the ECC key:
jws.SetPrivateKey(signatureIndex,eccKey);

// Set the payload.
var bIncludeBom = false;
var payloadStr = "In our village, folks say God crumbles up the old moon into stars.";
jws.SetPayload(payloadStr,"utf-8",bIncludeBom);

// Create the JWS
// By default, the compact serialization is used.
var jwsCompact = jws.CreateJws();
if (jws.LastMethodSuccess == false) {
    console.log(jws.LastErrorText);
    return;
}

console.log("JWS: " + jwsCompact);

// Note: ECC signatures use random values, so the output will be different each time a signature is produced.
// sample output:
// JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

// Now load the JWS, validate, and recover the original text.
var jws2 = new CkJws();

// Load the JWS.
success = jws2.LoadJws(jwsCompact);

var eccPubKey = new CkPublicKey();
eccKey.ToPublicKey(eccPubKey);

// Set the ECC public key used for validation.
signatureIndex = 0;
jws2.SetPublicKey(signatureIndex,eccPubKey);

// Validate the 1st (and only) signature at index 0..
var v = jws2.Validate(signatureIndex);
if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    console.log("Method call failed for some other reason.");
    console.log(jws2.LastErrorText);
    return;
}

if (v == 0) {
    console.log("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.");
    return;
}

// If we get here, the signature was validated..
console.log("Signature validated.");

// Recover the original content:
console.log(jws2.GetPayload("utf-8"));

// Examine the protected header:
var joseHeader = new CkJsonObject();
jws2.GetProtectedH(signatureIndex,joseHeader);
joseHeader.EmitCompact = false;

console.log("Protected (JOSE) header:");
console.log(joseHeader.Emit());

// Output:

// Signature validated.
// In our village, folks say God crumbles up the old moon into stars.
// Protected (JOSE) header:
// { 
//   "alg": "ES256"
// }