Encrypt the data with RSA private key. - Java Security

Java examples for Security:RSA

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Description

Encrypt the data with RSA private key.

Demo Code


import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

public class Main{
    /**/*  w w  w.  j  av a 2s.  c  o m*/
     * Key algorithm to be used in this class.
     */
    public static final String KEY_ALGORITHM = "RSA";
    /**
     * Encrypt the data with private key.
     *
     * @param data            data to be encrypted.
     * @param offset          offset of data to be encrypted.
     * @param length          length of data to be encrypted.
     * @param privateKeyBytes private key in binary format.
     * @return encrypted data.
     */
    public static byte[] encryptWithPrivateKey(byte[] data, int offset,
            int length, byte[] privateKeyBytes) {
        byte[] encryptedData = null;

        try {
            // Create a new PKCS8EncodedKeySpec with the given encoded key.
            PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(
                    privateKeyBytes);

            //RSA key factory.
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

            //Get the private key from the provided key specification.
            PrivateKey privateKey = keyFactory
                    .generatePrivate(pkcs8EncodedKeySpec);

            //Init the ciper.
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

            //Encrypt mode!
            cipher.init(Cipher.ENCRYPT_MODE, privateKey);

            //Do the encryption now !!!!
            encryptedData = cipher.doFinal(data, offset, length);

        } catch (NoSuchAlgorithmException | InvalidKeySpecException
                | NoSuchPaddingException | InvalidKeyException
                | IllegalBlockSizeException | BadPaddingException ex) {
            Logger.getLogger(RSAHelper.class.getName()).log(Level.SEVERE,
                    null, ex);
        }

        return encryptedData;
    }
}

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