(Java) ECDSA Sign and Verify Data using Different Hash Algorithms

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

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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 example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // First load an ECDSA private key to be used for signing.
    CkPrivateKey privKey = new CkPrivateKey();
    boolean success = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret");
    if (success == false) {
        System.out.println(privKey.lastErrorText());
        return;
        }

    // Load some data to be signed.
    CkBinData bd = new CkBinData();
    success = bd.LoadFile("qa_data/hamlet.xml");
    if (success == false) {
        System.out.println("Failed to load file to be hashed.");
        return;
        }

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

    // Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
    System.out.println("ECDSA signing the sha256 hash of the data...");
    String sig = ecdsa.signBd(bd,"sha256","base64",privKey,prng);
    System.out.println("sig = " + sig);

    // Verify the signature against the original data.
    // (We must use the same hash algorithm that was used when signing.)

    // Load the public key that corresponds to the private key used for signing.
    CkPublicKey pubKey = new CkPublicKey();
    success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem");
    if (success == false) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    CkEcc ecc2 = new CkEcc();
    int result = ecc2.VerifyBd(bd,"sha256",sig,"base64",pubKey);
    if (result != 1) {
        System.out.println(ecc2.lastErrorText());
        return;
        }

    System.out.println("Verified!");

    // ----------------------------------------------------------------------------------------
    // Let's do the same thing, but with sha384 hashing...

    System.out.println("--------------------------------------------");
    System.out.println("ECDSA signing the sha384 hash of the data...");

    sig = ecdsa.signBd(bd,"sha384","base64",privKey,prng);
    System.out.println("sig = " + sig);

    result = ecc2.VerifyBd(bd,"sha384",sig,"base64",pubKey);
    if (result != 1) {
        System.out.println(ecc2.lastErrorText());
        return;
        }

    System.out.println("Verified!");
  }
}