How safe is iMessage in the cloud?

Of all the problems iMessage has, Apple says it plans to solve a persistent one: having access to all your conversations on every device, instead of messages and data lying scattered across all the Macs, iPhones, and iPads you use. But is this the right problem to solve?Apple’s Craig Federighi explained at the 2017 Worldwide Developers Conference that iMessage will be stored in iCloud with “end-to-end encryption,” but provided no other details. Later, he mentioned that Siri tra