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I'm not sure if I completely agree with the silently part. Doesn't Signal have reproducible builds? In theory, any binary they release can be checked to see if

I'm not sure if I completely agree with the silently part. Doesn't Signal have reproducible builds? In theory, any binary they release can be checked to see if it corresponds to source code. Whether anyone is actually doing that is another question. And there is no technical reason app stores couldn't send a special backdoor-ed build to select list of users under surveillance if government forced them to. (They can target sets of users for staged roll-outs, beta programs, etc.) Which defeats the notion that one person watching can detect it for everybody. On the other hand, it's possible to do stuff with smart phones at the platform level. Whether through vulnerabilities or some platform capability (updates, etc.), it may be possible to have a backdoor-ed binary that looks to the user like it is the regular binary. That's not a capability that Signal has, but it is a capability that might very well exist. Regardless of all that, for users who have auto-updates enabled (most users), even if Signal can't silently push a backdoor-ed update, they can unilaterally push one. You could wake up tomorrow with a different version that has a backdoor, so even if you can identify backdoor-ed binaries, you have to turn off updates or verify the binary every time you open the app.

dane-pgp 7y ago
Assuming for a moment that we can trust our smart phones at the platform level not to lie to us, the problem of targeted backdoored builds could be mitigated somewhat if the platform implemented Binary Transparency in a clever way: https://wiki.mozilla.org/Security/Binary_Transparency https://wiki.mozilla.org/Security/Binary_Transparency When you install an app (whether through an app store, or side-loading) the app should state the location online of an append-only log that lists all the releases (with timestamps) for that app. The phone OS could periodically check to see if an upgrade is available, and security researchers could check that the log doesn't contain references to versions which aren't available to the public. Ideally there should perhaps also be a way for users to anonymously report which version of any app they are using, so that people with particular security concerns could configure their OS to only update an app after, for example, 50% of users have already installed the update.

dane-pgp 7y ago

Assuming for a moment that we can trust our smart phones at the platform level not to lie to us, the problem of targeted backdoored builds could be mitigated somewhat if the platform implemented Binary Transparency in a clever way: https://wiki.mozilla.org/Security/Binary_Transparency https://wiki.mozilla.org/Security/Binary_Transparency When you install an app (whether through an app store, or side-loading) the app should state the location online of an append-only log that lists all the releases (with timestamps) for that app. The phone OS could periodically check to see if an upgrade is available, and security researchers could check that the log doesn't contain references to versions which aren't available to the public. Ideally there should perhaps also be a way for users to anonymously report which version of any app they are using, so that people with particular security concerns could configure their OS to only update an app after, for example, 50% of users have already installed the update.