Patents that fuel Microsoft’s “Android tax” revealed in Chinese blog post

Microsoft(s msft) has long demanded licensing payments from Android device makers, but the identity of the relevant patents — which Microsoft uses to justify a so-called “Android tax” — has until now been something of a mystery.

The nature of those patents is now clearer, however, after the Chinese government published a list of 310 patents as part of an antitrust review into Microsoft’s acquisition of Nokia.

The patents on the list, as reported by Ars Technica, cover everything from GPS features to custom search tools to browsing functions. They also include standard-essential patents, as well as ones obtained in the “Rockstar” deal, in which a consortium of Google rivals jointly bought the intellectual property of defunct Canadian telco Nortel.

While Microsoft had announced in an April blog past that the Chinese government had identified “approximately 200 patent families that are necessary to build an Android smartphone,” it did not say which ones.

What it means

The fact that the patent list is now public could make it harder for Microsoft to browbeat companies into licensing deals. Until now, Microsoft’s strategy has involved telling the world that device makers are paying up, but failing to explain what exactly they are paying for — and, most likely, wrapping the whole process in non-disclosure deals.

The public nature of the list could make it easier for Android makers to design around the patents or else try to invalidate them in court. It could also trigger renewed debate in the U.S. over the country’s dysfunctional patent system which, by one account, has produced more than 250,000 smartphone-related patents.

For Microsoft, a lot is riding on the future of its Android licensing business. Recent reports suggest that the company could earn nearly $6 billion a year by 2017 if it gets a cut on even half of every Android device sold worldwide. Consumers, meanwhile, are less likely to be buoyed by the news that the Android platform, which is billed as free and open, could require a long-term Microsoft tax of $1 to $8 per device.