Key from String in Java RSA

Question

I am using in my app RSA cryptography. To store generated public key I convert it to String and then save it in database.

    Key publicKey=null;
    Key privateKey=null;

    KeyPair keyPair=RsaCrypto.getKeyPairRSA(1024);
    publicKey=keyPair.getPublic();
    privateKey=keyPair.getPrivate();



    String publicK=Base64.encodeToString(publicKey.getEncoded(), Base64.DEFAULT);
    String privateK=Base64.encodeToString(privateKey.getEncoded(), Base64.DEFAULT);

I save Strings publicK and privateK. My problem is, when I want to encrypt/decrypt text with RSA and use my saved Key in String format I don't know how to convert it to Key.

public static String encrypt(Key publicKey, String inputText){
    byte[]encodedBytes=null;
    String encryptedText="";
    try {
        Cipher cipher=Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        encodedBytes=cipher.doFinal(inputText.getBytes());
    } catch (Exception e) {Log.e("Error", "RSA encryption error");  }

    encryptedText=Base64.encodeToString(encodedBytes, Base64.DEFAULT);
    return encryptedText;
}

Do you have any idea? Thanks a lot

Solution

To convert publicK(String) to Public Key do as below :

byte[] keyBytes = Base64.decode(publicK.getBytes("utf-8"));
X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey key = keyFactory.generatePublic(spec);

To convert privateK(String) to Private Key do as below :

byte[] keyBytes = Base64.decode(privateK.getBytes("utf-8"));
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory fact = KeyFactory.getInstance("RSA");
PrivateKey priv = fact.generatePrivate(keySpec);

Comments

[rgreso]

thanks for answer. Eclipse shows me an error: The method decodeBase64(byte[]) is undefined for the type Base64. Could you help me with it please? thanks a lot

[rgreso]

Thanks for answer but it still shows an error, this time it wants another parameter: The method decode(byte[], int) in the type Base64 is not applicable for the arguments (byte[]) . Do you have any idea? Thanks a lot for your time

[txedo]

You can use Base64.encodeBase64String(byte[]) from Apache Commons Codec project.

[Dean Blakely]

I'm trying to do the same thing but PrivateKey priv = fact.generatePrivate(keySpec); gets InvalidDeySpecException saying I must use RSAPublicKeySpec but that won't take a byte[] as a parm

[Danylo.Vus]

try to change byte[] keyBytes = Base64.decode(privateK.getBytes("utf-8")); with byte[] keyBytes = Base64.decode(privateK, Base64.DEFAULT);