Apple's iOS security document includes details about how iMessage works

Apple’s iOS security document includes details about how iMessage works

Old news by this point (from a month ago), but worth mentioning by way of following up to my previous speculation: [1] [2] [3] [4]

It’s a very straightforward explanation (starting on page 20), and it’s in line with how others suspected or were able to discover that it works. The main point is that Apple intentionally designed a system such that they themselves are unable to read the messages passing through it. You can question whether or not it works as intended, but no other popular messaging service has even attempted this, as far as I know, and that makes it significant.