The guardian doesn’t call it that explicitly but that’s exactly what they have built here and I think the cover of a news app is brilliant in a lot of ways.
The only thing I would mention on top here as well is if you are planning to leak something using this app I still wouldn’t feel comfortable doing it on any device that could be investigated.
For example a work provided phone. While having the guardian app is itself in no way incriminating if you were to play out the scenario of an internal leak investigation at an organisation that has just ended up on the front pages of the guardian I think you could end up with a very short list by simply asking:
1. WHO had access to that information to begin with?
2. WHO had that app on their phone or the App Store shows it as previously downloaded or they wouldn’t make their phone available for inspection.
So if you’re in a scenario where you’re leaking something only known to a small group and / or your device can be inspected by someone relevant… I’d continue to strongly recommend making contact via a device that isn’t tied to you like your partner or someone you trust.
Remember, the ACTUAL goal here is to defeat the investigation and the best thing you can possibly do here is to not stand out from the crowd of suspects any more than anyone else.
There’s a very short link however between this app and the information you provided turning up in the guardian specifically that might not actually give you the cover you think you have (beyond the technical parts that they took care of which look brilliant for the record). But the next best thing by far I think you could do to help with that larger goal is to use a device not linked to you and that can’t be inspected to begin with.
I just wanted to point that out because it wasn’t called out in the threat model and I could realistically see people getting caught that way.
I would certainly recommend that readers not use a work phone, not only for the reasons you've stated but also that a lot of work devices use mobile device management software which is functionally spyware. To your point, dealing with having a very small anonymity set is tricky regardless of the technology used.
We do go to great lengths to make usage of the app to blow the whistle plausibly deniable. Data is segmented to "public" and "secret" repositories, where any secret data is stored within a fixed-sized/encrypted vault protected by a KDF technique that was developed by one of the team in Cambridge (https://eprint.iacr.org/2023/1792.pdf)
But of course, all this could be for nothing if you've just got corporate spyware on your device.
This is certainly something we've talked about internally but I've double checked the in-app FAQs and I think we could be more clear about recommending users not use on a work device, especially with MDM. We'll get that updated as soon as possible. Thanks!
-- edit
I should add that we do some basic detection devices that have been rooted or are in debug mode and issue a warning to the user before they continue. I'd be interested in what we can do to detect MDM software but I fear it might become a cat-and-mouse game so it's preferable that folks not use their work devices at all.
Edit: you might want to consider putting that warning about work devices in the app itself right before someone pushes forward with making potentially life changing decisions and doesn’t rely on them reading an FAQ. I see you already have an onboarding flow in place. It would be really simple to make that the first screen of it.
I'll see if we can get something together before the next app release. Thanks again!
ajb•10h ago
It's worth noting that in the UK, the official secrets act 1920 actually protected anonymous contacts with newspapers. It's a shame this was dropped in later legislation