Amazon, the online retail and technology giant owned by billionaire Jeff Bezos, won a patent in the US for a subscription feed that the company claims could “identify [Bitcoin] transaction participants” to help governments and law enforcement.

The patent, w filed in 2014 but approved on Tuesday, comes at a time when regulators’ desire to track and police cryptocurrency is running up against the technology’s core promises of anonymity for users. For Example ,user holding bitcoin are represented in the virtual currencies ledger by strings of text and numbers generated by a cryptographic algorithm. Taxation for Bitcoin thus relies on self-reporting. Amazon’s system, if implemented , could allow government subscribers to “correlate tax transaction data” with Bitcoin data in order to identify people, the patent filing says.

The patented system is described as a “streaming data marketplace” where various entities provide information into the stream to increase its identifying power, and customers subscribe to the feed for insights.

For example, the filing imagines a stream of transactions involving Bitcoin or another cryptocurrency—not very valuable on its own in terms of identifying people. But retailers in the stream can “combine the shipping address with the bitcoin transaction data” and publish the combined data to the stream; next, telecommunications companies “downstream” from the retailers may “correlate the IP (Internet Protocol) addresses of the transactions to countries of origin;” and further downstream, a government subscriber would “correlate tax transaction data.” With all of this data combined, stream subscribers may be able to identify Bitcoin users.

Amazon imagines that cops will be potential customers. Identifying Bitcoin users is a major project in global law enforcement, and the National Security Agency was working on it in 2013, documents from whistleblower Ed Snowden showed.

“For example, a law enforcement agency may be a customer and may desire to receive global bitcoin transactions, correlated by country, with ISP data to determine source IP addresses and shipping addresses that correlate to bitcoin addresses,” the Amazon patent filing states. “The streaming data marketplace may price this desired data out per GB (gigabyte), for example, and the agency can start running analytics on the desired data using the analysis module.”

Amazon did not immediately respond to Motherboard’s request for comment. The patent filing outlines that the “streaming data marketplace” would generally make it easier for various commercial and government entities to share information, and control who they share it with.

While a gigantic corporation like Amazon identifying Bitcoin users for police is no doubt a worrying thought for privacy-obsessed cryptocurrency fans, it’s worth emphasizing that tech companies regularly file all sorts of wild patents that never come to fruition. For example, in 2016 Amazon was awarded a patent for a system to deliver goods via a network of underground tunnels.

However, given the immense thirst from international and domestic agencies to identify Bitcoin users for a variety of reasons ranging from taxation to criminality, it’s clear that this patent has a little more going for it than tunnels to deliver my late-night Amazon Prime purchases.