Generate a RSA key pair with public key and private key. - Java Security

Java examples for Security:RSA

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Description

Generate a RSA key pair with public key and 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  . ja  va2 s  .  co  m*/
     * Key algorithm to be used in this class.
     */
    public static final String KEY_ALGORITHM = "RSA";
    /**
     * Default key length. The value shall be in the range of 512-65536.
     */
    private static final int KEY_LENGTH = 1024;
    /**
     * Identifier of pubic key in the Map.
     */
    public static final String PUBLIC_KEY = "PublicKey";
    /**
     * Identifier of private key in the Map.
     */
    public static final String PRIVATE_KEY = "PrivateKey";
    /**
     * Generate a RSA key pair with public key and private key.
     *
     * @param keyMap to save the key pair, the public key is indicated by
     *               "PublicKey" and private key is indicated by "PrivateKey".
     * @return
     */
    public static boolean generateKeyPair(Map<String, Object> keyMap) {
        //Get one instance of KeyPairGenerator with RSA.
        KeyPairGenerator keyPairGenerator = null;
        try {
            keyPairGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        } catch (NoSuchAlgorithmException ex) {
            Logger.getLogger(RSAHelper.class.getName()).log(Level.SEVERE,
                    null, ex);
            return false;
        }

        //Get a random seed.
        SecureRandom secureRandom = new SecureRandom();

        //Use current datetime as random seed.
        String currentDateTime = new SimpleDateFormat("yyyyMMddHHmmssSSS",
                Locale.getDefault()).format(new Date());
        secureRandom.setSeed(currentDateTime.getBytes());

        //Initialze the key generator with the random number provider. We need to call initialze everytime to get a NEW key pair.
        keyPairGenerator.initialize(KEY_LENGTH, secureRandom);

        //Ready to generate a key pair.
        KeyPair keyPair = keyPairGenerator.genKeyPair();

        //Get public and private key.
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        keyMap.put(PUBLIC_KEY, publicKey.getEncoded());
        keyMap.put(PRIVATE_KEY, privateKey.getEncoded());
        return true;
    }
}

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