How to encrypt decrypt with RSA keys in java

Question

I need to replace the encrypt and decrypt step from Unix to java code with the rsaprivatekey.pem and rsapublickey.pem keys generated with openssl

I generate the keys

openssl  genrsa  -out /tmp/rsaprivatekey.pem  -des3 1024
openssl rsa -in /tmp/rsaprivatekey.pem -pubout -out /tmp/rsapublickey.pem

i use the keys in unix (i need do it in java)

echo "Text to encript"| openssl rsautl -encrypt -inkey /tmp/rsapublickey.pem -pubin -out out.enc
openssl rsautl -decrypt -inkey /tmp/rsaprivatekey.pem -in out.enc

This was my attempt to do it

public static void main(String[] args) {


    Base64 base64 = new Base64();

    String TextStream = "this is the input text";
    byte[] Cipher;
    System.out.println("input:\n" + TextStream);
    Cipher = encrypt(TextStream);
    System.out.println("cipher:\n" + base64.encodeAsString(Cipher));
    System.out.println("decrypt:\n" + decrypt(Cipher));
}

private static byte[] encrypt(String Buffer) {
    try {

        Cipher rsa;
        rsa = Cipher.getInstance("RSA");
        rsa.init(Cipher.ENCRYPT_MODE, getPrivateKey(PRIVATE_PATH));
        return rsa.doFinal(Buffer.getBytes());
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}


private static String decrypt(byte[] buffer) {
    try {
        Cipher rsa;
        rsa = Cipher.getInstance("RSA");
        rsa.init(Cipher.DECRYPT_MODE, getPrivateKey(PUBLIC_PATH));
        byte[] utf8 = rsa.doFinal(buffer);
        return new String(utf8, "UTF8");
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

public static PrivateKey getPrivateKey(String filename) throws Exception {
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int) f.length()];
    dis.readFully(keyBytes);
    dis.close();

    PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return kf.generatePrivate(spec);
}

public static PublicKey getPublicKey(String filename) throws Exception {
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int) f.length()];
    dis.readFully(keyBytes);
    dis.close();

    X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return kf.generatePublic(spec);
}

but it not works, the PKCS8EncodedKeySpec/X509EncodedKeySpec are not correct... but i do not know what to put

Answer 1

Solution:

Thanks to @Sanjeev, using the bouncy castle API, I was able to encrypt/decrypt with the keys generated by openssl

public static void main(String[] args) throws IOException {

    Security.addProvider(new BouncyCastleProvider());

    KeyPair keyPair = readKeyPair(new File(PRIVATE_PATH), "pass"); 
    // if the private key is not encripted, pass can be anything.
    Key publickey = readPublicKey(new File(PUBLIC_PATH), "pass"); 
    Base64 base64 = new Base64();
    String text = "this is the input text";
    byte[] encripted;
    System.out.println("input:\n" + text);
    encripted = encrypt(keyPair.getPublic(), text);
    System.out.println("cipher:\n" + base64.encodeAsString(encripted));
    System.out.println("decrypt:\n" + decrypt(keyPair.getPrivate(), encripted));        
}

private static byte[] encrypt(Key pubkey, String text) {
    try {
        Cipher rsa;
        rsa = Cipher.getInstance("RSA");
        rsa.init(Cipher.ENCRYPT_MODE, pubkey);
        return rsa.doFinal(text.getBytes());
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}


private static String decrypt(Key decryptionKey, byte[] buffer) {
    try {
        Cipher rsa;
        rsa = Cipher.getInstance("RSA");
        rsa.init(Cipher.DECRYPT_MODE, decryptionKey);
        byte[] utf8 = rsa.doFinal(buffer);
        return new String(utf8, "UTF8");
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

private static KeyPair readKeyPair(File privateKey, String keyPassword) throws IOException {
    FileReader fileReader = new FileReader(privateKey);
    PEMReader r = new PEMReader(fileReader, new DefaultPasswordFinder(keyPassword.toCharArray()));
    try {
        return (KeyPair) r.readObject();
    } catch (IOException ex) {
        throw ex;
    } finally {
        r.close();
        fileReader.close();
    }
}

private static Key readPublicKey(File privateKey, String keyPassword) throws IOException {
    FileReader fileReader = new FileReader(privateKey);
    PEMReader r = new PEMReader(fileReader, new DefaultPasswordFinder(keyPassword.toCharArray()));
    try {
        return (RSAPublicKey) r.readObject();
    } catch (IOException ex) {
        throw ex;
    } finally {
        r.close();
        fileReader.close();
    }
}