Security Review: DTV coupon program

By Kevin Wallace at 6:20 pm on March 13, 2009Comments Off on Security Review: DTV coupon program

This June, all U.S. television stations must shut off their analog broadcasts, and replace them with digital ones. In order to make the transition less painful, the DTV Coupon Program offers up to two coupons to every U.S. household, good for up to $40 each off the price of a DTV converter box. I recently received mine, and a glance at the magnetic stripe on the back of the card made me wonder what security issues the program might have.


  • Consumer privacy / anonymity. If a consumer so chooses, they should be able to purchase a converter box with a coupon anonymously, revealing no personal information to the retailer, as if it were a cash transaction.
  • DTV subsidy funds. No one should be able to spend more than their allotted portion of the subsidy funds.


  • Retailers, who have financial incentive to uniquely identify and track consumers.
  • Malicious consumers, who wish to use more than their fair share of the subsidy funds.


  • It turns out that the magstripe of the cards contains the consumer’s full name, allowing retailers to personally identify them. This is not ever disclosed to the consumer. This could have been avoided by instead encoding a unique, but non-personally-identifiable token instead. A consumer may still be able to use their card anonymously after blanking out or replacing their name on the magstripe, or by using an online retailer like, who doesn’t ask for the name the card was issued under.
  • It might be possible for a single card to be used more than once, if two purchases are made using the same card simultaneously. If this is indeed the case, this attack could be prevented by using a two-phase commit to prevent a card from being pre-authorized for use more than once.


While there are still serious privacy concerns with the current system, it is not very costly to opt out of the system by paying an extra $40 for a converter box. On the other hand, the system appears to be relatively secure against malicious consumers, with no known attacks against it in the wild.

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