French conditional access vendor Viaccess used IBC this year as a launch platform for its new PC5 smart card based conditional access system. It says that it attacks an old problem in Control World sharing, that has got out of hand.
A control word is really the decryption key to a brief amount of content that is contained in what is called a crypto-period ‘ usually in pay TV a period of around 10 seconds of video, perhaps 300 frames. This key is actually sent at the front of the period, with the content, but is encrypted. It is decrypted by the smart card and sent back to the decoder unit in the set top.
The big problem is that out there, on existing Pay TV networks, there remain devices which send that decrypted control word to the decoder, in the clear. Modern ‘trusted’ set top boxes all re-encrypt the control word internally for these short hops, but some older devices don’t. It is much easier to intercept a decrypted control word (sometimes called an entitlement message) than it is to actually break the decoding algorithm on a smart card.
A pirate’s job then is to find one of these older devices, intercept the control word and set it up to send a decrypted version of it to other set tops, in just a few milliseconds, and now this has been taken up by organized crime syndicates, who bring together 10 or 20 such set tops and immediately refresh the system once one set top is taken off line. The control word is sent around the world over the internet, and has even been found rebroadcast on satellites, so that a set top can be setup to receive both the encrypted content and the ever changing illegal control word in two parallel satellite streams. It’s gone from being a family business, says Viaccess to networks involving 100,000s of homes, over the past few years.
Viaccess says that in PC5 it has introduced a way to bind a unique identity number of the smart card to the decrypted control word, and then look for these in the wild. It is a simple matter to find a single instance of a control word, use it to identify the particular set top it came form, and then adjust the output from the control world server, so that this particular set top is now blocked, virtually in real time.
‘We are also using elements of behavioral analysis,’ said Fran’ois Moreau de Saint Martin, CEO of Viacess, ‘so for instance if a smart card is set up to decrypt 12 channels at once, that’s not something that it would naturally do in any home.’
Viaccess is a France Telecom subsidiary and says that it has chased pirates around the world with crime fighting organizations such as Interpol, as set tops and signals are transferred in a complex distribution network for the control word.
Viaccess has adopted a strategy of refreshing cards every 24 months to try to remain one step ahead of piracy and says that on this platform it can refresh exactly how the algorithms for this control word fix works in existing devices, with an over the air update on existing devices, just in case any pirate finds a way around it. The only other way to fix it, says Viaccess is to replace all the older set tops out there and that will cost pay TV operators too much.
PC5 also has defenses against modified smartcards and smartcard emulations, but Viaccess declined to go into further detail about how these worked.