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

Please, please, please do not store unencrypted private keys in your database. If you have to store private keys that's known as escrowing and you should be encrypting them with a symmetric key only known to your application. — KyleM, Apr 06 '14 at 22:27
Thank you, yes I am thinking about it. Could you give me an advice, what is the best way to store a key in app?thanks — rgreso, Apr 06 '14 at 22:56
use a password protected Java keystore. Look up Java keytool... — KyleM, Apr 07 '14 at 00:56

score 13 · Answer 1 · edited Nov 11 '16 at 12:44

13

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);

edited Nov 11 '16 at 12:44

Mark W

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answered Apr 06 '14 at 22:21

baldguy

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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 Apr 06 '14 at 22:43
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 – rgreso Apr 07 '14 at 06:22
You can use Base64.encodeBase64String(byte[]) from Apache Commons Codec project. – txedo Oct 01 '14 at 11:28
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 – Dean Blakely Oct 01 '15 at 21:37
try to change byte[] keyBytes = Base64.decode(privateK.getBytes("utf-8")); with byte[] keyBytes = Base64.decode(privateK, Base64.DEFAULT); – Danylo.Vus Jan 24 '18 at 19:18

score 0 · Answer 2 · edited Mar 23 '17 at 12:34

0

I can only assume the line:

PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(clear);

with "clear" was meant to be "keyBytes"

edited Mar 23 '17 at 12:34

Robin Kanters

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answered Jul 23 '15 at 02:34

user3005339

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Key from String in Java RSA

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