The bytes can be converted back to public and private key objects : KeyPairGenerator « Security « Java Tutorial

1. Java Tutorial
2. Security
3. KeyPairGenerator

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.EncodedKeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class Main {
  public static void main(String[] argv) throws Exception {
    String algorithm = "DSA"; // or RSA, DH, etc.

    // Generate a 1024-bit Digital Signature Algorithm (DSA) key pair
    KeyPairGenerator keyGen = KeyPairGenerator.getInstance(algorithm);
    keyGen.initialize(1024);
    KeyPair keypair = keyGen.genKeyPair();
    PrivateKey privateKey = keypair.getPrivate();
    PublicKey publicKey = keypair.getPublic();

    byte[] privateKeyBytes = privateKey.getEncoded();
    byte[] publicKeyBytes = publicKey.getEncoded();
    
    KeyFactory keyFactory = KeyFactory.getInstance(algorithm);
    EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
    PrivateKey privateKey2 = keyFactory.generatePrivate(privateKeySpec);

    EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyBytes);
    PublicKey publicKey2 = keyFactory.generatePublic(publicKeySpec);

    // The orginal and new keys are the same
    boolean same = privateKey.equals(privateKey2); 
    same = publicKey.equals(publicKey2); 
  }
}