(Java) Duplicate openssl dgst -sha256 -sign private.pem -out sha256.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -sign private.pem -out sha256.sig in.dat

1. Creates a SHA256 digest of the contents of the input file
2. Signs the SHA256 digest using the private key.

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux, Solaris 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[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkPrivateKey pkey = new CkPrivateKey();

    // Load the private key from an PEM file:
    boolean success = pkey.LoadPemFile("private.pem");
    if (success != true) {
        System.out.println(pkey.lastErrorText());
        return;
        }

    CkRsa rsa = new CkRsa();

    // Import the private key into the RSA component:
    success = rsa.ImportPrivateKeyObj(pkey);
    if (success != true) {
        System.out.println(rsa.lastErrorText());
        return;
        }

    // OpenSSL uses big-endian.
    rsa.put_LittleEndian(false);

    // Load the file to be signed.
    CkBinData bdFileData = new CkBinData();
    success = bdFileData.LoadFile("in.dat");

    CkBinData bdSig = new CkBinData();
    success = rsa.SignBd(bdFileData,"sha256",bdSig);
    if (success != true) {
        System.out.println(rsa.lastErrorText());
        return;
        }

    // Save the binary signature to a file.
    success = bdSig.WriteFile("signature.sig");
    if (success != true) {
        System.out.println("Failed to write signature.sig.");
        return;
        }

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