A satellite TV system must face the following challenge: it is one-way. The receivers cannot do anything but receive; they cannot emit anything.
- Each subscriber has a smartcard, and that card contains a key Ks specific to that subscriber.
- The media stream is encrypted with a key K. That key is updated regularly.
- Along with the media stream, the publisher sends K encrypted with each Ks in circulation. That is, every minute or so, thousands of small blobs are sent in some "holes" in the data stream (apparently there is sufficiently free bandwidth for that); all these blobs contain K, but encrypted with the key of a subscriber.
Thus, a given decoder will just wait for the blob which contains K encrypted with his card-specific key Ks, and use the card to obtain K and decrypt the stream.
When a subscriber is no longer a subscriber (he ceased to pay), the publisher simply stops sending the blob containing K encrypted with the corresponding Ks. The next time K is updated (it happens several times per day), the ex-subscriber is "kicked out".
In older times, media publishers had the habit of doing everything "their way", which means that they designed their own encryption algorithms, and they were very proud of them, and kept them secret. Of course, such secrets were never maintained for long because reverse engineering works well; and, inevitably, these homemade encryption algorithms almost invariably turned out to be pathetically weak and breakable.
Nowadays, the publishers have begun to learn, and they use proper encryption. In such a situation, the only recourse for attackers is to clone smartcards, i.e. break their way through the shielding of a legally obtained smartcard, to get the Ks of that card. Breaking through a smartcard is expensive, but not infeasible, at least for the kind of smartcard that are commonly used for such things; it requires a high-precision laser and an electronic microscope, and is rumoured to cost "a few thousands of dollars" for each break-in. Attackers do just that.
Publishers react in the following way: with traditional police methods. The cloning method is worth the effort only if thousands of clones can be sold, as part of some underground market. Inspectors just masquerade as buyers, obtain a clone, see what card identity the clone is assuming, and deactivate the corresponding subscriber identity on the publisher side, evicting all clones of that card in one stroke.
From what I have seen, the break-clone-sell-detect-deactivate cycle takes about two weeks. It is more-or-less an equilibrium: the non-subscribers who accept the semi-regular breakage of connectivity are in sufficient numbers to maintain professional pirates, but they are not numerous enough to really endanger the publishers' business model.
We may note that Blu-ray discs are a much more challenging model, because readers can be off-line and must still work; and though each Blu-ray reader embeds its own reader-specific key, there is not enough room on a Blu-ray disc to include "encrypted blobs" for all readers in circulation. They use a much more advanced algorithm called AACS. However, for satellite TV, the simple method described above works well.what design is on each oreo how project finance works how workers comp works in california which science is the hardest who solution for diarrhea how much solution in little green machine which entrepreneur is a craftsman how much science diet to feed cat who science division where is temple from design star whose expertise who product information how much project coordinators make from where designers buy fabric which london airport is closer to the city how startup valuation works where do technology come from how many technology in the world where to develop old film which design principle is shown in the illustration how much science do we know where london congestion charge which technology hides the existence of data what science is taught in 9th grade where teachers work where to get technology news where's device manager where is solution in geography where engineering controls are not sufficient who developed the polio vaccine how much london to paris train how company shares work when can you expect technology to be effective where are workers going why business ethics is important how tech savvy are you interview answer when tech bytes ltd where to find device id on android how much developing an app cost how to go from store manager to district manager how many project zorgo members are there what products contain benzene when product patent started in india who set up paypal where are guest workers from how manufacture a product is 1 8 miles far where company number how manufacturing rubber what london is famous for what system is the spleen in what products to use for curly hair how many device can airpod pro connect how manufacture cement when device is offline where to donate technology near me when entrepreneurship started product where name how startup founders make money when london stock market open where is roadmap in jira what development did you find where to find engineering jobs how many solutions are there to this nonlinear system where to watch project runway how much science diet to feed my dog when science meets religion where to find company financial statements how long does solution finish last who science council upsc how teaching has changed when business partners fall out where to find device manager in windows 10 why startups fail summary where to donate technology near me who roadmap ntds how farm products which company was responsible for love canal what is the solution process where is made in made in how technological factor influence volkswagen how much technology is used in the world how much startup capital for small business how much engineering technician make how many project runway seasons how much technology is used in schools when system testing is performed how many device can use hulu how workers comp works in florida startup who is mara jira roadmap which version which products of fire are health hazards how much system 12 itoto whose education system is the best how many system calls are there in linux how much teaching english in thailand what management style is most effective for you how many entrepreneur are there whom comma which london airport is better where system preferences mac how often should aims be done why management consulting interview answer which product is an example of a consumer good how much company worth which products contain benzene how london became londongrad roadmap to or roadmap for how many science regents are required to graduate startup who is rebecca stroud what company is enhypen under who should be ceo of startup who project in ku where to solve physics problems how start up a small business whose project is nlex and slex why workers are fleeing the hospitality sector what device on a resuscitation bag mask
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