Padding error when using RSA Encryption in C# and Decryption in Java
- by Matt Shaver
Currently I am receiving the following error when using Java to decrypt a Base64 encoded RSA encrypted string that was made in C#:
javax.crypto.BadPaddingException: Not PKCS#1 block type 2 or Zero padding
The setup process between the exchange from .NET and Java is done by creating a private key in the .NET key store then from the PEM file extracted, created use keytool to create a JKS version with the private key. Java loads the already created JKS and decodes the Base64 string into a byte array and then uses the private key to decrypt.
Here is the code that I have in C# that creates the encrypted string:
public string Encrypt(string value) {
byte[] baIn = null;
byte[] baRet = null;
string keyContainerName = "test";
CspParameters cp = new CspParameters();
cp.Flags = CspProviderFlags.UseMachineKeyStore;
cp.KeyContainerName = keyContainerName;
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(cp);
// Convert the input string to a byte array
baIn = UnicodeEncoding.Unicode.GetBytes(value);
// Encrypt
baRet = rsa.Encrypt(baIn, false);
// Convert the encrypted byte array to a base64 string
return Convert.ToBase64String(baRet);
}
Here is the code that I have in Java that decrypts the inputted string:
public void decrypt(String base64String) {
String keyStorePath = "C:\Key.keystore";
String storepass = "1234";
String keypass = "abcd";
byte[] data = Base64.decode(base64String);
byte[] cipherData = null;
keystore = KeyStore.getInstance("JKS");
keystore.load(new FileInputStream(keyStorePath), storepass.toCharArray());
RSAPrivateKey privateRSAKey = (RSAPrivateKey) keystore.getKey(alias, keypass.toCharArray());
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.DECRYPT_MODE, privateRSAKey);
cipherData = cipher.doFinal(data);
System.out.println(new String(cipherData));
}
Does anyone see a step missing or where the padding or item needs to be changed? I have done hours of reading on this site and others but haven't really found a concrete solution.
You're help is vastly appreciated.
Thanks. -Matt
