Asymmetric Android RSA Encrypt - Decrypt .NET

Question

I am encrypting on JAVA using RSA and attempting to decrypt using .NET. I am including my Android code and .NET code in hopes that someone has some experience with this sort of thing.

Android Code:

   byte[] modulusBytes = Base64.decode("xTSiS4+I/x9awUXcF66Ffw7tracsQfGCn6g6k/hGkLquHYMFTCYk4mOB5NwLwqczwvl8HkQfDShGcvrm47XHKUzA8iadWdA5n4toBECzRxiCWCHm1KEg59LUD3fxTG5ogGiNxDj9wSguCIzFdUxBYq5ot2J4iLgGu0qShml5vwk=");
   byte[] exponentBytes = Base64.decode("AQAB");
   BigInteger modulus = new BigInteger(1, modulusBytes );               
   BigInteger exponent = new BigInteger(1, exponentBytes);

   RSAPublicKeySpec rsaPubKey = new RSAPublicKeySpec(modulus, exponent);
   KeyFactory fact = KeyFactory.getInstance("RSA");
   PublicKey pubKey = fact.generatePublic(rsaPubKey);

   Cipher cipher = Cipher.getInstance("RSA");
   cipher.init(Cipher.ENCRYPT_MODE, pubKey);

   byte[] plainBytes = new String("big kitty dancing").getBytes("UTF-8");
   byte[] cipherData = cipher.doFinal( plainBytes );
   String encryptedString = Base64.encodeBytes(cipherData);

From this JAVA Code I take the results of the encryptedString which happen to be:

FoP4+AAIH6hcabXnrvNG5YUk/nBv9n9HU0CAgZjkIWQIDjbOpSwoPVBFERrZ6641x2QaoJw5yv18XAay+0WrCaSw4sveRX+hmPm5qeVUPcjoR4slsVZ/hBFJtAHj9tva4hOugWDZa9s3RVJlxkNfE+u+Kt/YKLOi2EYbH05HjeM=

And attempt to decrypt using the following .NET code

 const int PROVIDER_RSA_FULL = 1;
   const string CONTAINER_NAME = "Tracker";

   CspParameters cspParams;
   cspParams = new CspParameters(PROVIDER_RSA_FULL);
   cspParams.KeyContainerName = CONTAINER_NAME;
   RSACryptoServiceProvider rsa1 = new RSACryptoServiceProvider(cspParams);
   rsa1.FromXmlString("<RSAKeyValue><Modulus>xTSiS4+I/x9awUXcF66Ffw7tracsQfGCn6g6k/hGkLquHYMFTCYk4mOB5NwLwqczwvl8HkQfDShGcvrm47XHKUzA8iadWdA5n4toBECzRxiCWCHm1KEg59LUD3fxTG5ogGiNxDj9wSguCIzFdUxBYq5ot2J4iLgGu0qShml5vwk=</Modulus><Exponent>AQAB</Exponent><P>+lXMCEwIN/7+eMpBrq87kQppxu3jJBTwztGTfXNaPUTx+A6uqRwug5oHBbSpYXKNDNCBzVm/0VxB3bo4FJx+ZQ==</P><Q>yasOGaJaE9xlF9T2xRuKeG9ZxCiyjhYaYB/mbtL+SIbtkRLi/AxaU4g2Il/UxhxhSXArKxIzV28zktispPJx1Q==</Q><DP>ueRgQIEFUV+fY979a1RgrVHIPpqEI1URhOMH3Q59oiXCcOumM5njyIHmWQxRAzXnG+7xlKXi1PrnRll0L4oOKQ==</DP><DQ>dfEMNgG1HJhwpxdtmqkYuoakwQvsIRzcIAuIAJh1DoWaupWJGk8/JEstHb1d+t7uJrzrAi2KyT/HscH2diE0YQ==</DQ><InverseQ>YoYF9PF6FiC0YngVeaC/eqt/ea8wMYNN3YO1LuzWpcy2exPRj2U0ZbWMvHXMUb4ea2qmhZGx1QlK4ULAuWKpXQ==</InverseQ><D>g1WAWI4pEK9TA7CA2Yyy/2FzzNiu0uQCuE2TZYRNiomo96KQXpxwqAzZLw+VDXfJMypwDMAVZe/SqzSJnFEtZxjdxaEo3VLcZ1mnbIL0vS7D6iFeYutF9kF231165qGd3k2tgymNMMpY7oYKjS11Y6JqWDU0WE5hjS2X35iG6mE=</D></RSAKeyValue>");

   string data2Decrypt =    "FoP4+AAIH6hcabXnrvNG5YUk/nBv9n9HU0CAgZjkIWQIDjbOpSwoPVBFERrZ6641x2QaoJw5yv18XAay+0WrCaSw4sveRX+hmPm5qeVUPcjoR4slsVZ/hBFJtAHj9tva4hOugWDZa9s3RVJlxkNfE+u+Kt/YKLOi2EYbH05HjeM=";

   byte[] encyrptedBytes = Convert.FromBase64String(data2Decrypt);  

   byte[] plain = rsa1.Decrypt(encyrptedBytes, false);
   string decryptedString = System.Text.Encoding.UTF8.GetString(plain);

Answer 1

The lesson here is don't rely on defaults. You should replace the line

   Cipher cipher = Cipher.getInstance("RSA");

with the line

   Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING");

in your Java code.