(Java) ECDSA Sign Data and Verify Signature

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature.

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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 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.

    // Use Chilkat Crypt2 to generate a hash for any of the following
    // hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

    CkCrypt2 crypt = new CkCrypt2();
    crypt.put_HashAlgorithm("SHA256");
    crypt.put_Charset("utf-8");
    crypt.put_EncodingMode("base64");

    // Hash a string.
    String hash1 = crypt.hashStringENC("The quick brown fox jumps over the lazy dog");
    System.out.println("hash1 = " + hash1);

    // Or hash a file..
    String hash2 = crypt.hashFileENC("qa_data/hamlet.xml");
    System.out.println("hash2 = " + hash2);

    // (The Crypt2 API provides many other ways to hash data..)

    // -----------------------------------------------------------
    // An ECDSA private key is used for signing.  The public key is for signature verification.
    // Load our ECC private key.
    // Our private key file contains this:

    // 	// -----BEGIN PRIVATE KEY-----
    // 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
    // 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
    // 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
    // 	-----END PRIVATE KEY-----

    CkPrivateKey privKey = new CkPrivateKey();
    boolean success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem");
    if (success != true) {
        System.out.println(privKey.lastErrorText());
        return;
        }

    // We'll need a PRNG source for random number generation.
    // Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
    CkPrng prng = new CkPrng();

    // Sign the hash..
    CkEcc ecdsa = new CkEcc();
    String ecdsaSigBase64 = ecdsa.signHashENC(hash1,"base64",privKey,prng);
    if (ecdsa.get_LastMethodSuccess() != true) {
        System.out.println(ecdsa.lastErrorText());
        return;
        }

    System.out.println("ECDSA signature = " + ecdsaSigBase64);

    // -----------------------------------------------------------
    // Now let's verify the signature using the public key.

    CkPublicKey pubKey = new CkPublicKey();
    success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pubkey.pem");
    if (success != true) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    int result = ecdsa.VerifyHashENC(hash1,ecdsaSigBase64,"base64",pubKey);
    if (result == 1) {
        System.out.println("Signature is valid.");
        return;
        }

    if (result == 0) {
        System.out.println("Signature is invalid.");
        return;
        }

    if (result < 0) {
        System.out.println(ecdsa.lastErrorText());
        System.out.println("The VerifyHashENC method call failed.");
        return;
        }
  }
}