[GranPC]

They use remote attestation based on SGX. So, assuming SGX can be trusted, yes. See https://signal.org/blog/private-contact-discovery/

[dathinab]

and assuming you have a practical way to

- verify the attestation

- make sure it means the code they have published is the attested code

- make sure the published code does what it should

- and catch any divergence to this *fast enough* to not cause much damage

....

it's without question better then doing nothing

but it's fundamentally not a perfect solution

but it's very unclear if there even is a perfect solution, I would guess due to the characteristics of phone numbers there isn't a perfect solution

[mjg59]

Well, no - as long as someone you trust is able to do that verification, that's good enough.