iPhone maker Apple Inc. has confirmed in a newly released security document that it’s one of Google LLC’s highest profile cloud customers.

The document, first obtained by CNBC, shows that Apple began using Google’s cloud infrastructure sometime within the last 10 months, possibly at the expense of Google’s main public cloud rivals, Amazon Web Services Inc. and Microsoft Corp.

Apple has been using AWS and Microsoft’s Azure cloud storage services to host documents within its iCloud service since 2011.

However, it was reported back in 2016 that Apple was looking to lessen its reliance on Amazon’s services and migrate some of its data to the Google Cloud Platform. Reports at the time suggested that the shift from AWS to Google would net the latter firm some $400 million to $600 million.

Now, an update to the iOS Security Guide, a document Apple uses to explain the measures it takes to ensure the security of iOS and the privacy of its customers, specifically mentions Google as one of its supporting partners. The updated guide also removes any mention of Microsoft, which was listed as a partner in earlier editions.

That’s not to say Apple has ditched Microsoft as a partner, one analyst told SiliconANGLE. Holger Mueller, principal analyst and vice president of Constellation Research Inc., said Apple is almost certainly not dropping Microsoft because doing so would be way too difficult.

However, Mueller did note that it’s not impossible that Apple would one day be able to reduce its reliance on third-party data center operators. “In its statement on the repatriation of profits, Apple also said that it will invest into data centers,” he said. “So in the long run this business may come back to Apple.”

Nonetheless, whatever happens later on down the road, Mueller said that the news is still a notable achievement for Google, one that edges it closer to its main public cloud rivals.

“It’s an important win for Google to get substantial load for the Google Cloud Platform,” Mueller continued. “Load matters as it drives economies of scale, and those drive costs and prices down. With AWS and Azure already previously confirmed [as Apple partners], it means Google is now getting a share of the load too.”

Apple’s guide doesn’t say when Apple began using Google’s infrastructure, but a previous version of the document updated in March 2017 doesn’t mention Google, which means the move must have taken place during a ten-month window following that date.

In the document, Apple was keen to stress that Google has no means of accessing any of its users’ iCloud data due to the encryption Google’s cloud employs.

“Each file is broken into chunks and encrypted by iCloud using AES-128 and a key derived from each chunk’s contents that utilizes SHA-256,” Apple says in the document. “The keys and the file’s metadata are stored by Apple in the user’s iCloud account. The encrypted chunks of the file are stored, without any user-identifying information, using third-party storage services, such as S3 and Google Cloud Platform.”

What that means is that Google would only see encrypted data, with no way of knowing whom that data belonged to. Apple is also rather guarded about the specifics of its third-party servers, so it’s quite possible that individual users’ data is spread across multiple storage platforms.

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