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Signal app downloads spike as US protesters seek message encryption

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Re: Signal app downloads spike as US protesters seek message encryption

#22

Earlier quoted context omitted.

Key management is still centralized and controlled by Apple, so they can still MITM communications by messing with the key exchange. iCloud backups (enabled by default) are not end-to-end encrypted. So while it's technically E2E, in practice you get very little protection from it because it's broken by design. I still use iMessage because of the user experience, but let's not be fooled by their misleading E2E claims;…

If both parties disable iCloud on their phones, does Apple have any way to read messages sent via iMessage?

We have no idea and there’s no real way even in principle for us to know.

Re: Signal app downloads spike as US protesters seek message encryption

#23

Honest question for those in the know: If I wanted to run my own personal “analysis” to verify the security of Signal, where would I start? Is it even possible? Just curious if there was a way to “know” rather than “trust”.

The first step would probably involve getting a PhD in cryptography...

Re: Signal app downloads spike as US protesters seek message encryption

#24
post #16
post #10

Earlier quoted context omitted.

How do you know that the binary you run actually corresponds to the source code you read? EDIT: and would you then also review every commit to make sure nothing bad gets introduced? No, at some point you have to place trust in the vendor, the developers, independent audits, etc.

How do you know the compiler actually compiles the source code to the binary you expect without injecting backdoors? How do you know that the hardware actually follows the instructions in the binary as they are specified? How do you know you're not living in a computer simulation in which the operators can access your data without any backdoors whatsoever?

Build it yourself.

Re: Signal app downloads spike as US protesters seek message encryption

#25

One has to wonder about behind the scenes heuristics as it pertains to taking a chance distributing a backdoored version sideloaded into the App Stores. One also wonders about whether the encryption or app are possibly compromised generally (even if the source is vetted and distributions are verified) Perhaps most of interest though would be how many phones are owned otherwise, to give access to the protester Signal…

Signal does a pretty good job at minimizing the metadata it has access to. For example, the app can tell you who of your contacts has Signal installed but the Signal service itself never gets to see your contacts ( https://signal.org/blog/private-contact-discovery/ ).

The problem is that in many countries, one's phone number is already killer metadata: it is linked to your identity, because you cannot purchase a SIM card without showing ID (a copy of which is made and sent to the authorities). Consequently, a repressive state can determine which of its citizens has installed Signal, and merely using an app known for privacy might already be grounds for persecution.

Apparently Signal is working on identifiers different from a user's phone number, but it is not clear how many people will actually take advantage of this feature.

Re: Signal app downloads spike as US protesters seek message encryption

#26
post #16
post #10

Earlier quoted context omitted.

How do you know that the binary you run actually corresponds to the source code you read? EDIT: and would you then also review every commit to make sure nothing bad gets introduced? No, at some point you have to place trust in the vendor, the developers, independent audits, etc.

How do you know the compiler actually compiles the source code to the binary you expect without injecting backdoors? How do you know that the hardware actually follows the instructions in the binary as they are specified? How do you know you're not living in a computer simulation in which the operators can access your data without any backdoors whatsoever?

To make an apple pie from scratch, first you must create the universe. :)

Re: Signal app downloads spike as US protesters seek message encryption

#27
post #10

Earlier quoted context omitted.

How do you know that the binary you run actually corresponds to the source code you read? EDIT: and would you then also review every commit to make sure nothing bad gets introduced? No, at some point you have to place trust in the vendor, the developers, independent audits, etc.

You can build the source locally, then compare the MD5 hash value of your build to (1) the hash value they post publicly for their build and (2) the actual hash value of their build once you download it. Assuming all three match, you know that the binary matches the source. Someone who is more technically inclined can probably go into more detail on this.

we are talking about security, and you brought up... MD5?

Re: Signal app downloads spike as US protesters seek message encryption

#28
post #10

Earlier quoted context omitted.

How do you know that the binary you run actually corresponds to the source code you read? EDIT: and would you then also review every commit to make sure nothing bad gets introduced? No, at some point you have to place trust in the vendor, the developers, independent audits, etc.

You can build the source locally, then compare the MD5 hash value of your build to (1) the hash value they post publicly for their build and (2) the actual hash value of their build once you download it. Assuming all three match, you know that the binary matches the source. Someone who is more technically inclined can probably go into more detail on this.

This is actually more involved than it sounds. It is pretty easy for the compiler to introduce nondeterminism and result in slightly different binaries. I know this for a fact because I fixed a couple bugs like this in LLVM.

For the curious: we actually were intentional about finding these, by compiling many programs with the same parameters on different machines. One with a 32 bit OS and toolchain, the other one on a 64 bit machine, and we would get alerted when we produced binaries with a different checksum.

Re: Signal app downloads spike as US protesters seek message encryption

#30

Earlier quoted context omitted.

will only happen if phone manufactures ship them by default rather than the unsecure by default ones they ship atm. Sounds crazy when I say it outloud...

iMessage is end to end encrypted by default. Perhaps not as strongly, but it's a good default to begin with.

Whenever key management is centralized, there is basically no security from the legal authority in the jurisdiction that the messaging vendor is located in. The vendor can always push you an MITM key. They can even show you the "correct" recipient key when you physically verify but use a different one for the actual message transfer and this would be a trivial easy to obfuscate switch in the program binary.

E2E with centralized key management is primarily to protect you from casual/private threats (vendor employees, snoopers in your or your recipients network) not from legal authority.

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