[dwaite]

> They can increase security by breaking a single target into multiple targets, by increasing competition around security and privacy issues, by having more people use and work with the protocols and able to spot potential problems, by encouraging more transparency around issues when they arise, and by having alternatives readily available if one of the clients is found to be compromised or insecure.

I believe you are speaking to transparency, not third party clients.

Beeper Mini actually bundled binaries that they didn't understand to bootstrap registration. They could only attempt to be compatible with messages that they have received, and verify messages they send show up correctly - they cannot know they covered all available options.

I speak to this as someone who reverse engineered MSN Messenger back in the early 2000s for an XMPP gateway - you'd occasionally find an entirely new type of message (requiring an entirely new parsing code path for their undocumented/bespoke messaging protocol) because someone registered for a stock ticker or the like.

There was no fuzzing the official servers or clients to see if they were robust or secure - the goal was to have a salable product. In fact, we saw other messaging systems where we had significant concerns based on our understanding of the protocols through reverse engineering, and we saw one vendor exploit a security vulnerability in their own shipping product in order to verify authenticity and block third party clients (which worked for a period of time)

From what I saw of the iMessage system, third party support is not going to be feasible even with a documented protocol without partnership, because there is an assumption of attestation of real, unique hardware as part of registration to prevent mass abuse.

[person3]

I don’t know a lot about how it works, so forgive me if this is a silly idea. I wonder if attestation could be done using real Apple devices, while leaving the private key on the user’s android. So similar to the old beeper to get the signed attestation, and send the result to the phone. Still could be secure since you can keep the private key used to encrypt messages local on the users device. I guess the issue might be a cat and mouse game if detecting beepers flock of Apple hardware to try and disable them all… (given many people would be using the same Apple devices)

[dwaite]

I think iMessage is still using older attestations, but generally an attestation of this sort (App Attest, Play Protect API) represent a chain of the hardware, boot process, OS and application.

So iMessage is not going to be willing to hand out private keys or negotiate them for a third party application, and Beeper will not be trusted to register a private key itself.

Android iMessage support would be weird because there is no iMessage application - there is an application which lets you send SMS and to upgrade to MMS or iMessage when available. So, if there ever was an official Messages app for Android, I would somewhat expect it to also offer to take over being the default application for SMS/MMS.