(Java) 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 v9.5.0.66 or greater.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // 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.
    CkStringBuilder 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("}");

    CkPrivateKey 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..)
    boolean success = eccKey.LoadJwk(sbJwk.getAsString());
    if (success != true) {
        System.out.println(eccKey.lastErrorText());
        return;
        }

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

    CkJws jws = new CkJws();

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

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

    // Set the payload.
    boolean bIncludeBom = false;
    String 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.
    String jwsCompact = jws.createJws();
    if (jws.get_LastMethodSuccess() != true) {
        System.out.println(jws.lastErrorText());
        return;
        }

    System.out.println("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.
    CkJws jws2 = new CkJws();

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

    CkPublicKey eccPubKey = eccKey.GetPublicKey();

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

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

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

    // If we get here, the signature was validated..
    System.out.println("Signature validated.");

    // Recover the original content:
    System.out.println(jws2.getPayload("utf-8"));

    // Examine the protected header:
    CkJsonObject joseHeader = jws2.GetProtectedHeader(signatureIndex);
    if (jws2.get_LastMethodSuccess() != true) {
        System.out.println("No protected header found at the given index.");
        return;
        }

    joseHeader.put_EmitCompact(false);

    System.out.println("Protected (JOSE) header:");
    System.out.println(joseHeader.emit());

    // Output:

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