Currently I'm trying to create a single-sign on solution, and I was having trouble because sometimes (but not always) the encrypted text would fail to decrypt. I found out that the later .net versions have stricter checking for valid characters. So when the encrypted byte array was converted to a string, the encoding process would create characters that the stricter decoding process did not like. This article on msdn's .net security blog finally helped me out.
First posted on 12/8/2014 8:10:58 PM