Padding error when using RSA Encryption in C# and Decryption in Java
c#, encryption, java, rsa
Solution
Check that you have correctly exchanged the key.
Trying to decrypt with an incorrect key is indistinguishable from decrypting badly padded data.
Problem
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