here is an example which encodes a serial bit stream with rc4 and transmits is as a manchester coded bit stream.The manrcv decodes the manchester data stream and decoding the rc4 is the same as coding it .the carrier detect output from the manchesetr decoder is used as the start signal for the rc4 decoder so that the random number generators start at the same point.
data rates of upto 50 Mbps are easily achieved using the xilinx or altera tool sets.
http://www.8052.com/users/jezwoldspage/Rc4s.zip