(Java) Get EC Public Key from EC Private Key

Demonstrates how to get an EC public key from an EC private key.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux Java Libs for Android

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[])
  {
    boolean success = false;

    // We have an ECC private key...
    // The contents of the private key PEM file look like this:

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

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

    // Get the public key.
    CkPublicKey pubKey = new CkPublicKey();
    privKey.ToPublicKey(pubKey);

    // Save the public key to a PEM file.
    success = pubKey.SavePemFile(false,"qa_data/ecc/secp256r1-pubkey.pem");
    if (success == false) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    // The contents of the ECC public key PEM file look like this:

    // 	-----BEGIN PUBLIC KEY-----
    // 	MIIBSzCCAQMGByqGSM49AgEwgfcCAQEwLAYHKoZIzj0BAQIhAP////8AAAABAAAA
    // 	AAAAAAAAAAAA////////////////MFsEIP////8AAAABAAAAAAAAAAAAAAAA////
    // 	///////////8BCBaxjXYqjqT57PrvVV2mIa8ZR0GsMxTsPY7zjw+J9JgSwMVAMSd
    // 	NgiG5wSTamZ44ROdJreBn36QBEEEaxfR8uEsQkf4vOblY6RA8ncDfYEt6zOg9KE5
    // 	RdiYwpZP40Li/hp/m47n60p8D54WK84zV2sxXs7LtkBoN79R9QIhAP////8AAAAA
    // 	//////////+85vqtpxeehPO5ysL8YyVRAgEBA0IABOVKaiLPKEDChhkA64UEBOXT
    // 	v/VFHnhrUPN+bXqCvEl7rroAYpH5tKzbiGTtMSlp4JO9Pxg44zeX7EoWDvOrpD0=
    // 	-----END PUBLIC KEY-----

    System.out.println("Success.");
  }
}