Java

RSA Sign with PKCS8 Encrypted Key

See more RSA Examples

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it). Java

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;

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

    CkPrivateKey privKey = new CkPrivateKey();

    // Load the private key from an RSA PEM file:
    success = privKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789");
    if (success == false) {
        System.out.println(privKey.lastErrorText());
        return;
        }

    CkRsa rsa = new CkRsa();

    // Import the private key into the RSA component:
    success = rsa.UsePrivateKey(privKey);
    if (success == false) {
        System.out.println(rsa.lastErrorText());
        return;
        }

    // This example will sign a string, and receive the signature
    // in a hex-encoded string.  Therefore, set the encoding mode
    // to "hex":
    rsa.put_EncodingMode("hex");

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

    // Sign the string using the sha256 hash algorithm.
    // Other valid choices are sha1, sha384, sha512 and others.
    String hexSig = rsa.signStringENC(strData,"sha256");
    if (rsa.get_LastMethodSuccess() == false) {
        System.out.println(rsa.lastErrorText());
        return;
        }

    System.out.println(hexSig);

    // Now verify with the public key.
    // This example shows how to use the public key from 
    // a digital certificate (.cer file)
    CkCert cert = new CkCert();
    success = cert.LoadFromFile("raul_publicKey.cer");
    if (success == false) {
        System.out.println(cert.lastErrorText());
        return;
        }

    CkPublicKey pubKey = new CkPublicKey();
    cert.GetPublicKey(pubKey);

    CkRsa rsa2 = new CkRsa();
    success = rsa2.UsePublicKey(pubKey);
    if (success == false) {
        System.out.println(rsa2.lastErrorText());
        return;
        }

    // Verify the signature against the original data:
    rsa2.put_EncodingMode("hex");
    success = rsa2.VerifyStringENC(strData,"sha256",hexSig);
    if (success == false) {
        System.out.println(rsa2.lastErrorText());
        return;
        }

    System.out.println("Signature verified!");

    // Verify with incorrect data:
    success = rsa2.VerifyStringENC("something else","sha256",hexSig);
    if (success != true) {
        System.out.println("Signature not verified! (which was expected in this case)");
        }
    else {
        System.out.println("Hmmm... that's not right...");
        }
  }
}