Authorization Error while rendering the Jasper Report - urlencode

Question

Occasionally getting "Unauthorized Error" when my Base64 encoded token contains a "+" sign (which is a valid Base 64 character)
I am using Visualize-JS to render the Jasper report in MVC Boilerplate. To authenticate every request, I am using the pre authorization flow where I am sending a Base64 encoded token from my application and on Jasper server decoding it.
Everything is working fine except, occasionally I am getting "Unauthorized Error". When I checked I found it is only failing when my Base64 encoded token contains a "+" sign (which is a valid Base 64 character). My C# code is URL encoding the + sign as %2B whereas the Java code while decoding the same URL converts %2B into a space. (Note - I am encoding in C# and decoding in Java since, Jasper server only supports JAR files).
Is anyone else facing this or have faced earlier and found the solution?
For now, as a work around I am replacing the space with a + sign but, I am searching for a better solution.
Here is the faulty token, C# code for encoding and Java code for decoding
Token - f0NNFeJKfvBiWZP7I7vTGHb8yhiDEmkoE35p6ueQceBiMUJbPoaF927UsHn7w2AdCbKmfjjfZyKxm8iwrTo37kLZPE91EuT4WJrQ/KjQ+r0=
C# Code for Encryption -
public string Encrypt(string plainText)
{
byte[] plainBytes = Encoding.UTF8.GetBytes(plainText);
return HttpUtility.UrlEncode(Convert.ToBase64String(Encrypt(plainBytes, GetRijndaelManaged(_config.EncryptionKey))));
}
public RijndaelManaged GetRijndaelManaged(string secretKey)
{
byte[] keyBytes = new byte[16];
byte[] secretKeyBytes = Encoding.UTF8.GetBytes(secretKey);
Array.Copy(secretKeyBytes, keyBytes, Math.Min(keyBytes.Length, secretKeyBytes.Length));
return new RijndaelManaged
{
Mode = CipherMode.CBC,
Padding = PaddingMode.PKCS7,
KeySize = 128,
BlockSize = 128,
Key = keyBytes,
IV = keyBytes
};
}
public byte[] Encrypt(byte[] plainBytes, RijndaelManaged rijndaelManaged)
{
return rijndaelManaged.CreateEncryptor().TransformFinalBlock(plainBytes, 0, plainBytes.Length);
}
Java Code - encryptedText here is the token mentioned above
public String decrypt(String encryptedText){
encryptedText = decode(encryptedText);
byte[] cipheredBytes = Base64.getDecoder().decode(encryptedText);
byte[] keyBytes = getKeyBytes(secretKey);
return new String(decrypt(cipheredBytes, keyBytes, keyBytes), "UTF-8");
}
public static String decode(String url)
{
try {
String prevURL="";
String decodeURL=url;
while(!prevURL.equals(decodeURL))
{
prevURL=decodeURL;
decodeURL=URLDecoder.decode( decodeURL, "UTF-8" );
}
return decodeURL.replace(" ", "+");
} catch (UnsupportedEncodingException e) {
return "Issue while decoding" +e.getMessage();
}
}
private byte[] getKeyBytes(String key) throws UnsupportedEncodingException{
byte[] keyBytes= new byte[16];
byte[] parameterKeyBytes= key.getBytes("UTF-8");
System.arraycopy(parameterKeyBytes, 0, keyBytes, 0, Math.min(parameterKeyBytes.length, keyBytes.length));
return keyBytes;
}