Java Security

I've been writing some code to sign data. So far this is what I have

public void encryptHash(String hashToEncrypt, String pathOfKey, String Algorithm) {
    FileInputStream fis = null;
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    int len;

        File f = new File(pathOfKey);

        fis = new FileInputStream(pathOfKey);
        len = 0;
        while((len = fis.read()) != -1){
            baos.write(len);
        }

        KeyFactory kf = KeyFactory.getInstance(Algorithm); //Algorithm = "RSA"
        KeySpec keySpec = new PKCS8EncodedKeySpec(baos.toByteArray());
        baos.close();
        PrivateKey privateKey = kf.generatePrivate(keySpec);  //Here's the exception thrown

        Signature rsaSigner = Signature.getInstance("SHA1withRSA");
        rsaSigner.initSign(privateKey);

        fis = new FileInputStream(hashToEncrypt);
        BufferedInputStream bis = new BufferedInputStream(fis);
        byte[] buffer = new byte[1024];
        len = 0;
        while((len = bis.read(buffer)) >= 0){
            try {
                rsaSigner.update(buffer, 0, len);
            } catch (SignatureException ex) {
                Logger.getLogger(DataEncryptor.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
        bis.close();

        byte[] signature = rsaSigner.sign();

        System.out.println(new String(signature));
}

The problem is that I'm getting the following exception and I can't find infomation about it.

dic 09, 2011 12:49:02 PM firmaelectronica.DataEncryptor encryptHash
Grave: null
java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: IOException : DER input, Integer tag error
    at sun.security.rsa.RSAKeyFactory.engineGeneratePrivate(RSAKeyFactory.java:217)
    at java.security.KeyFactory.generatePrivate(KeyFactory.java:372)
    at firmaelectronica.DataEncryptor.encryptHash(DataEncryptor.java:40)
    at firmaelectronica.FirmaElectronica.main(FirmaElectronica.java:39)
Caused by: java.security.InvalidKeyException: IOException : DER input, Integer tag error
    at sun.security.pkcs.PKCS8Key.decode(PKCS8Key.java:361)
    at sun.security.pkcs.PKCS8Key.decode(PKCS8Key.java:367)
    at sun.security.rsa.RSAPrivateCrtKeyImpl.<init>(RSAPrivateCrtKeyImpl.java:91)
    at sun.security.rsa.RSAPrivateCrtKeyImpl.newKey(RSAPrivateCrtKeyImpl.java:75)
    at sun.security.rsa.RSAKeyFactory.generatePrivate(RSAKeyFactory.java:316)
    at sun.security.rsa.RSAKeyFactory.engineGeneratePrivate(RSAKeyFactory.java:213)

What does DER input, Integer tag error means? How can I read a password-protected PKCS8 DER private key to sign a file?

Thanks so much in advance !!!!!

Edited by: 879653 on 09-dic-2011 15:44