[Java] RSA BadPaddingException : data must start with zero
- by Robin Monjo
Hello everyone.
I try to implement an RSA algorithm in a Java program. I am facing the "BadPaddingException : data must start with zero".
Here are the methods used to encrypt and decrypt my data :
public byte[] encrypt(byte[] input) throws Exception
{
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");//
cipher.init(Cipher.ENCRYPT_MODE, this.publicKey);
return cipher.doFinal(input);
}
public byte[] decrypt(byte[] input) throws Exception
{
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");///
cipher.init(Cipher.DECRYPT_MODE, this.privateKey);
return cipher.doFinal(input);
}
privateKey and publicKey attributes are read from files this way :
public PrivateKey readPrivKeyFromFile(String keyFileName) throws IOException {
PrivateKey key = null;
try {
FileInputStream fin = new FileInputStream(keyFileName);
ObjectInputStream ois = new ObjectInputStream(fin);
BigInteger m = (BigInteger) ois.readObject();
BigInteger e = (BigInteger) ois.readObject();
RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e);
KeyFactory fact = KeyFactory.getInstance("RSA");
key = fact.generatePrivate(keySpec);
ois.close();
}
catch (Exception e) {
e.printStackTrace();
}
return key;
}
Private key and Public key are created this way :
public void Initialize() throws Exception
{
KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA");
keygen.initialize(2048);
keyPair = keygen.generateKeyPair();
KeyFactory fact = KeyFactory.getInstance("RSA");
RSAPublicKeySpec pub = fact.getKeySpec(keyPair.getPublic(), RSAPublicKeySpec.class);
RSAPrivateKeySpec priv = fact.getKeySpec(keyPair.getPrivate(), RSAPrivateKeySpec.class);
saveToFile("public.key", pub.getModulus(), pub.getPublicExponent());
saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent());
}
and then saved in files :
public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException {
FileOutputStream f = new FileOutputStream(fileName);
ObjectOutputStream oos = new ObjectOutputStream(f);
oos.writeObject(mod);
oos.writeObject(exp);
oos.close();
}
I can't figured out how the problem come from. Any help would be appreciate !
Thanks in advance.
