RC4CSP information
The RC4CryptoServiceProvider class is a wrapper around the RC4 crypto service provider from the CryptoAPI. This class supports key lengths from 8 to 2048 bits. if the CSP doesn't support the specified key size, the RC4CryptoServiceProvider class automatically reverts to the ARCFourManaged class to perform cryptographic transformations. The Microsoft CSPs typically support keys between 40 and 128 bits.