(Java) Compute JWK Thumbprint for RSA and EC Public Keys

Demonstrates how to compute a JSON Web Key thumbprint for a public key (RSA or ECC).

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[])
  {
    CkPublicKey pubKey = new CkPublicKey();

    // A public key can be loaded from any format (binary DER, PEM, etc.)
    // This example will load the public keys from JWK format, 
    // and will then compute the JWK thumbprint.

    // First do it for an RSA public key...

    CkStringBuilder sb = new CkStringBuilder();
    sb.Append("{");
    sb.Append("\"kty\": \"RSA\",");
    sb.Append("\"n\": \"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAt");
    sb.Append("VT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn6");
    sb.Append("4tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FD");
    sb.Append("W2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n9");
    sb.Append("1CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINH");
    sb.Append("aQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw\",");
    sb.Append("\"e\": \"AQAB\",");
    sb.Append("\"alg\": \"RS256\",");
    sb.Append("\"kid\": \"2011-04-29\"");
    sb.Append("}");

    // The JWK format is automatically detected..
    boolean success = pubKey.LoadFromString(sb.getAsString());
    if (success != true) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    // Get the JWK thumbprint (using SHA256)
    System.out.println("JWK thumbprint: " + pubKey.getJwkThumbprint("SHA256"));

    // Output:
    // JWK thumbprint: NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs

    // --------------------------------------------------------------
    // Now let's do an EC public key:
    sb.Clear();
    sb.Append("{ ");
    sb.Append("  \"kty\": \"EC\",");
    sb.Append("  \"crv\": \"P-256\",");
    sb.Append("  \"x\": \"tDeeYABgKEAbWicYPCEEI8sP4SRIhHKcHDW7VqrB4LA\",");
    sb.Append("  \"y\": \"J08HOoIZ0rX2Me3bNFZUltfxIk1Hrc8FsLu8VaSxsMI\"");
    sb.Append("}");

    success = pubKey.LoadFromString(sb.getAsString());
    if (success != true) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    // Get the JWK thumbprint (using SHA256)
    System.out.println("JWK thumbprint: " + pubKey.getJwkThumbprint("SHA256"));

    // Output:
    // JWK thumbprint: 8fm8079s3nu4FLV_7dVJoJ69A8XCXn7Za2mtaWCnxR4
  }
}