Java Requires Chilkat v11.0.0+

RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature. Chilkat2 Java

import com.chilkatsoft.chilkat2.Cert;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.PrivateKey;
import com.chilkatsoft.chilkat2.PublicKey;
import com.chilkatsoft.chilkat2.Rsa;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example assumes the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        PrivateKey privKey = new PrivateKey();

        // Load the private key from an RSA .key file:
        try {
            privKey.loadPemFile("privateKey.key");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        Rsa rsa = new Rsa();

        // Import the private key into the RSA component:
        try {
            rsa.usePrivateKey(privKey);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Create the signature as a hex string:
        rsa.setEncodingMode("hex");

        String strData = "This is the string to be signed.";

        // Sign the string using the sha256 hash algorithm.
        // Other valid choices are "md2", "sha1", "sha384",
        // "sha512", and "md5".
        String hexSig = rsa.signStringENC(strData, "sha256");

        System.out.println(hexSig);

        // Load a digital certificate from a .cer file:
        Cert cert = new Cert();

        try {
            cert.loadFromFile("myCert.cer");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        PublicKey pubKey = new PublicKey();
        cert.getPublicKey(pubKey);

        // Now verify using a new instance of the RSA object:
        Rsa rsa2 = new Rsa();

        // Import the public key into the RSA object:
        try {
            rsa2.usePublicKey(pubKey);

            // The signature is a hex string, so make sure the EncodingMode is correct:
            rsa2.setEncodingMode("hex");

            // Verify the signature:
            rsa2.verifyStringENC(strData, "sha256", hexSig);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

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