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Comment by staltz | Hacker News Reader

Cross device identity is still an issue, but not a problem in the foundation. It's a matter of making client apps (like Patchwork) recognize a message of type "link this and that account together" and then your friend's app would automatically follow both accounts and render them as if they are the same thing. It'll be done eventually in Patchwork.

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Yeah that is what they were talking about when I was following the project. Once that is done in patchwork, I might try using it again.

It will be a must once mobile is launched, which I'm working on.

Is it also possible to use multiple devices without leaking from which device each message was posted?

Well, yes and no. The log will show a different id (public key) which authored the message. But the device itself (iPhone or Google Nexus or whatever) doesn't need to be mentioned.

That could leak information a user doesn't want to be leaked, like at which hours he is at work (using the work computer) etc. Which id belongs to which device could probably be inferred when the service is used actively.

I understand that transparency might not be a design goal or techinically possible, I'm just raising the concern.

Can't I just share my private key across multiple devices?

Those sound like pretty unavoidable, and often acceptable, drawbacks.

Nothing stops you from copy-pasting your asymmetric keys (it's a file) to different devices. I bet it's feasible, the biggest issue is also making sure your log stays the same, because a log shouldn't get forked.

Is there a reason you can't just use the same key pair on both devices?

yes. 1) it would be significantly less secure - compromising either device would compromise both. Imagine an airplane with two engines that needs both to fly - a single engine plane is actually safer - because the chance of loosing one of one is less than the chance of loosing one of two, (assuming chance of engine failure is independent) Use a separate key on each device is like a two engine plane that can still fly with one engine - this is significantly safer than a single engine plane.

2) it would greatly complicate the replication protocol, having to take into account forks, rather than assuming append only, where you can represent the current synced state with a single counter.

I'm having trouble following this and the reply thread below. Why is identity device-specific? So every time a get a new computer I have a new public key?

You can also use the same keypair on multiple devices. This however results in another problem: You could post content from both devices simultaneously. But the underlying protocol requires each message to refer to the previous message by the same identity. So if two different devices post a message without having received the message of the other one, one of the messages is considered invalid.

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