I included Security.Cryptography into my src code but ARCFourManaged class (that i used in it) was not found while runnig the program. I was surprised because i also used RijndaelManaged class and there were no problems with it. I thought that both are in Security.Cryptography but they are obviuosly not. pls help what to do so that i can used ARCFourManaged...thx