Is there a function that convert a string to RSA keys?

Question

I'm trying to save an RSA key pair (Public/Private) into a database in a String format and then retrieve them from the database and convert them back into (Public key/ Private key) format.

I tried the following code; the first function generates the public/private code and the last two functions is for converting a string to a key pair format.

    public static Voter generateKeyPair(Voter v) throws NoSuchAlgorithmException {
    KeyPairGenerator kpg = KeyPairGenerator.getInstance("DSA");
    kpg.initialize(2048, new SecureRandom(v.getPassword().getBytes()));
    KeyPair kp = kpg.generateKeyPair();
    PrivateKey privKey = kp.getPrivate();
    PublicKey pubKey = kp.getPublic();
    String pubKeyString = new BigInteger(pubKey.getEncoded()).toString(64);
    String privKeyString = new BigInteger(privKey.getEncoded()).toString(64);
    v.setPrivateKey(privKeyString);
    v.setPublicKey(pubKeyString);
    return v;
    }

public static Key getPublicKey(String keyString) throws GeneralSecurityException, IOException {
    byte[] key = Base64.getDecoder().decode((keyString.getBytes()));
    X509EncodedKeySpec spec = new X509EncodedKeySpec(key);
    KeyFactory fact = KeyFactory.getInstance("DSA");
    PublicKey pub = fact.generatePublic(spec);
    return pub;
}

public static Key getPrivateKey(String keyString) throws GeneralSecurityException, IOException {
    byte[] key = Base64.getDecoder().decode(keyString.getBytes());
    PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(key);
    KeyFactory fact = KeyFactory.getInstance("DSA");
    PrivateKey priv = fact.generatePrivate(keySpec);
    return priv;

}

First thing, I got the value for the public key > private key which doesn't make sense.

When I try to run the code I get the following error: java.security.spec.InvalidKeySpecException: Inappropriate key specification: IOException: DerInputStream.getLength(): lengthTag=13, too big.

Do you really need to store those keys as Strings? When saving them as string you will have to deal with proper encoding. You could just save them as binary data in your db. — Michał Krzywański, Apr 07 '19 at 20:43
Base64 encode it. The duplicate shows you how to reverse it. — Elliott Frisch, Apr 07 '19 at 20:51

Is there a function that convert a string to RSA keys?

0 Answers0