The answer is &quot;GCM may reveal more to Google than one would expect from using an E2E encryption application (like metadata, and more than one would initially assume)&quot;.<p>The person I initially replied to was talking about Google, GCM, E2E encryption, and that metadata won&#x27;t reveal anything to Google except time&#x2F;date of a single message and the message size. I pointed out there may be more information there.<p>I have no doubt that the NSA can do traffic analysis, or may have some of this data already... I&#x27;m not sure why that is in the replies to my comments in this thread.