How to store a key pair inside a variable so that it will not change

How do I get this key pair out and store it so that it won't change and I will be able to use the same keypair to encrypt and decr开发者_C百科ypt in separate applications ? I am encrypting a string eg ("1234A") with the public key from this key pair and storing it into a database. For the decrypt part, I am getting the encrypted string out from the database and decrypting it using the private key from the same keypair.

public static KeyPair generateKey () throws NoSuchAlgorithmException
{                    
    KeyPairGenerator keyGen = KeyPairGenerator.getInstance ("RSA");      
    keyGen.initialize(1024);         
    KeyPair key = keyGen.generateKeyPair();        
    return key;    
}

The KeyPair class implements Serializable, as do its component parts PrivateKey and PublicKey. You could serialize to a byte stream and store this in your database?

First you need to get the public and the private key from your KeyPair with:

 PrivateKey priv = key.getPrivate();
    PublicKey pub = key.getPublic();

This method will write the keys to a file, which you can later use to decrypt/verify in a separate application:

public void writeToFile(PrivateKey priv, PublicKey pub){
        byte[] keyBytes = priv.getEncoded();

        FileOutputStream privOut;
        try {
            privOut = new FileOutputStream(privateName);

        privOut.write(keyBytes);
        privOut.close();

        FileOutputStream pubOut = new FileOutputStream(publicName);
        byte[] pubKeyBytes = pub.getEncoded();
        pubOut.write(pubKeyBytes);
        pubOut.close();


        } catch (FileNotFoundException e) {
        } catch (IOException e) {
            }   
        }

KeyPair is serializable, so you might serialize it to a file or the db and deserialize it in all applications.