Le Cryptage RSA, un Décryptage Android

Je me suis mise en œuvre d'une démo pour le RSA de Chiffrement et de Déchiffrement dans Android. Je peux Effectuer de Chiffrement très bien, mais Dans le Déchiffrement j'obtiens une Exception: >>java.security.InvalidKeyException: unknown key type passed to RSA.

    KeyPairGenerator kpg;
KeyPair kp;
PublicKey publicKey;
PrivateKey privateKey;
byte [] encryptedBytes,decryptedBytes;
Cipher cipher,cipher1;
String encrypted,decrypted;
public String RSAEncrypt (final String plain) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException 
{
kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(1024);
kp = kpg.genKeyPair();
publicKey = kp.getPublic();
privateKey = kp.getPrivate();
cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
encryptedBytes = cipher.doFinal(plain.getBytes());
encrypted = new String(encryptedBytes);
System.out.println("EEncrypted?????"+encrypted);
return encrypted;
}
public String RSADecrypt (final String result) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException 
{
cipher1=Cipher.getInstance("RSA");
cipher1.init(Cipher.DECRYPT_MODE, privateKey);
decryptedBytes = cipher1.doFinal(result.getBytes());
decrypted = new String(decryptedBytes);
System.out.println("DDecrypted?????"+decrypted);
return decrypted;
}

Et je suis l'appel de la fonction à partir d'ici:

encrypt.setOnClickListener(new OnClickListener()
{ 
public void onClick(View arg0) 
{
try
{
RSAEncrypt rsaencrypt=new RSAEncrypt();
rsaencrypt.RSAEncrypt(name);
result=rsaencrypt.RSAEncrypt(name);
Toast.makeText(getBaseContext(), result.toString(),Toast.LENGTH_SHORT).show();
System.out.println("Result:"+result);
}
catch(Exception e)
{
e.printStackTrace();
Toast.makeText(getBaseContext(), e.toString(),Toast.LENGTH_LONG).show();
}
}
});
decrypt.setOnClickListener(new OnClickListener()
{ 
public void onClick(View arg0) 
{
{
try
{
RSAEncrypt rsadecrypt=new RSAEncrypt();
rsadecrypt.RSADecrypt(result);
ans=rsadecrypt.RSADecrypt(result);
System.out.println("Result is"+ans);
Toast.makeText(getBaseContext(), ans.toString(),Toast.LENGTH_LONG).show();
}
catch(Exception e)
{
e.printStackTrace();
Toast.makeText(getBaseContext(), e.toString(),Toast.LENGTH_LONG).show();
System.out.println("Exception is>>"+e);
}
}
});