Damien Bally a ?crit : > Hello > > As far as I know there is a plugin named sc (softcam) that allows someone to > view encrypted channels. > Can anyone explain the way it works ? > Don't misunderstand me : I don't want an howto to do something illegal, just > some theory to satisfy my curiosity. SC replaces the hardware CAM, when you have a budget card with no CI (connector for the CAM). It can be a fully software CAM, or use a smartcard reader to use the subscription card you have. Another missing part in common budget card is the descrambler chip, which can be replaced by a software one. The scrambling algo is called CSA (common scrambling algorithm). I don't know what can be considered illegal there, except when you do not use a valid subscription card. There is less in all this than in DeCSS, which includes keys (ie. smartcard) + key management (ie. SC) + algo (ie FFdeCSA). The theory behind that is roughly : * the stream contains information about key management algo * it also contains random bytes (like a public key) * the CAM must use one of it's internal key management algo, along with those bytes, to select the appropriate private key inside the smartcard * it then transmits the key to the descrambling chip, that does the actual descrambling * the whole process is repeated at each channel change, and also from time to time, I think I hope I didn't upset anyone with that... -- NH
