<a href="http:&#x2F;&#x2F;www.apple.com&#x2F;business&#x2F;docs&#x2F;iOS_Security_Guide.pdf" rel="nofollow">http:&#x2F;&#x2F;www.apple.com&#x2F;business&#x2F;docs&#x2F;iOS_Security_Guide.pdf</a><p>Page 41, Second paragraph:
&quot;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 Amazon S3 and Windows Azure.&quot;