Error while decrypt a signature

Question

I have my own RSA privateKey and create a signature for my data by the following way: digest my data, then encrypt digested data with my RSA privateKey. When receive this signature, I decrypt it with my RSA publicKey, but there's a error message: Invalid PKCS#1 padding: no leading zero!
I already use RSA privateKey to sign with DSA too, but denied.
How to solve this problem? Or we could only sign with DSA? Or is there any way to convert RSA keys to DSA keys
Thanks

Answer 1

I digest a UserName then encrypt with a PrivateKey, but when decrypt with the PublicKey, they're not the same
Anyone know why?
Here is my codes:
public byte[] Encrypt(){
try{
byte[] b = MakeDigest(strUser.getBytes());
Cipher rsa = Cipher.getInstance("RSA/ECB");
// Encrypt using Client's PrivateKey
rsa.init(Cipher.ENCRYPT_MODE,CprivateKey);
byte[] encrypted = rsa.doFinal(b);
rsa.init(Cipher.DECRYPT_MODE,CpublicKey);
byte[] encrypted_1 = rsa.doFinal(encrypted);
System.out.println(encrypted.equals(encrypted_1)); // false
return encrypted;
}catch(Exception ex){
System.out.println(ex.getMessage());
return null;
private byte[] MakeDigest(byte[] bUser){
try{
MessageDigest md = MessageDigest.getInstance("SHA");
md.update(bUser);
return md.digest();
}catch(Exception ex){
return null;
}