>Even Edward Snowden, the well known American Whistleblower, claims “I use Signal every day.”
Well, 5 years ago...
Well, 5 years ago...
It it without a doubt that he is under constant electronic and physical surveillance by the Russian and American governments. His phones and computers are also very likely compromised. At that point your choice of messenger app matters about as much as the color of your socks because the interception is happening at another layer.
Two key words in your comment are both spectrums: trust and privacy.
Most people implicitly trust their hardware more than Snowden does now -- they overestimate the security from the factory and he probably has better expectations of the likelihood of hardware compromise.
On the privacy spectrum, one point is how much privacy you think you have, and the other (unknown) point is how much you actually have. Similarly, I think Snowden's situation and prior experience helps him more accurately understand where those points are; the rest of us are up on the first peak of the Dunning-Kreuger chart.
How to keep it free of custom targeted malware? That is another question!
But one can use Session (a fork of Signal) over Lokinet (an onion routing network, which is similar to Tor).
Even the updated version of Signal merely relays stuff through a proxy. That is, there's just one hop, and that's trivial to deanonymize. With Lokinet, there are multiple hops, so adversaries must compromise multiple nodes.
Also, Session requires no PII for account creation. That's great for anonymity, but there's no built-in authentication. So users must authenticate contacts in meatspace or via other communication channels.
Creating a new service node requires a providing a stake in Loki, which I believe currently costs on the order of $5000. And the only source is Loki held by existing service nodes. So arguably, as the creation rate for new service nodes increases, the price of the requisite Loki stake increases, perhaps supra linearly, or even exponentially.
There's also the issue that service nodes that behave maliciously lose all of their Loki, both the initial stake, and anything that they've earned.
I don't know specifics, however. So I don't know just how high the bar is for malicious service nodes.