Natanael

But once a process is running its trivial to get weeks of extremely detailed history and lots of secrets you thought were ephemeral

Recall was set to be default on for everybody and to record everything in a database which is trivial to extract data from.

There's a lot of nonsense Apple is doing too (like the chatgpt integration) but they didn't put keylogger into the system.

Neither of these mention networks, only protocols/schemes, which are concepts. Cryptography exists outside networks, and outside computer science (even if that is where it finds the most use).

This is ridiculous rules lawyering and isn't even done well. Such schemes inherently assume multiple communicating parties. Sure you might not need to have a network but you still have to have distinct devices and a communication link of some sort (because if you have a direct trusted channel you don't need cryptography)

You're also wrong about your interpretation.

Here's how to read it:

At point A both parties create their long term identity keys.

At point B they initiate a connection, and create session encryption keys with a key exchange algorithm (first half of PFS)

At point C they exchange information over the encrypted channel.

At point D the session keys are automatically deleted (second half of PFS)

At point E the long term key of one party is leaked. The contents from B and C can not be recovered because the session key is independent of the long term key and now deleted. This is forward secrecy. The adversary can't compromise it after the fact without breaking the whole algorithm, they have to attack the clients as the session is ongoing.

This is motivated for example by how SSL3.0 usually was used with a single fixed RSA keypair per server, letting user clients generate and submit session encryption keys - allowing a total break of all communications with the server of that key is comprised. Long term DH secrets were also often later used when they should be single use. Then we moved on to ECDH where generating new session secrets is fast and everybody adopted real PFS.

Yes compromising the key means you often get stuff like the database too, etc. Not the point! If you keep deleting sensitive data locally when you should then PFS guarantees it's actually gone, NSA can't store the traffic in their big data warehouse and hope to steal the key later to decrypt what you thought you deleted. It's actually gone.

And both of the above definitions you quoted means the same as the above.

In any case, both of these scenarios create an attack vector through which an adversary can get all of your old messages, which, whether you believe violates PFS by your chosen definition or not, does defeat its purpose (perhaps you prefer this phrasing to "break" or "breach").

Playing loose with definitions is how half of all broken cryptographic schemes ended up insecure and broken. Being precise with attack definitions allows for better analysis and better defenses.

Like how better analysis of common attacks on long running chats with PFS lead to "self healing" properties being developed to counter point-in-time leaks of session keys by repeatedly performing key exchanges, better protecting long term keys by for example making sure software like Signal make use of the OS provided hardware backed keystore for it, etc. All of this is modeled carefully and described with precise terms.

Edit: given modern sandbox techniques in phones, most malware and exploits doesn't survive a reboot. If malware can compromise your phone at a specific time but can't break the TPM then once you reboot and your app rekeys then the adversary no longer have access, and this can be demonstrated with mathematical proofs. That's self healing PFS.

Anyone can start a forum.

Fair point, but my cryptography forum (reddit.com/r/crypto) has regulars that include people writing the TLS specifications and other well known experts. They're hanging around because the forum is high quality, and I'm able to keep quality high because I can tell who's talking bullshit and who knows their stuff.

decoupled

Assuming it's a pun

Tasker also have the autonotification plugin which let you set any rules and actions you want on notifications

Once again reminding you that I run a cryptography forum (I've done so for one 10 years, I keep up to date on the field) and it's a term defined by professional cryptographers.

https://www.sectigo.com/resource-library/perfect-forward-secrecy

https://link.springer.com/referenceworkentry/10.1007/978-1-4419-5906-5_90

https://www.sciencedirect.com/topics/computer-science/forward-secrecy

Literally all definitions speak of network traffic and leaked / extracted encryption keys. PFS is about using short term keys that you delete so that they can not leak later.

Backup and sync via a separate mechanism is not a PFS violation. In particular because they're independent of that same encrypted session. It's entirely a data retention security issue.

Matrix.org supports message log backup via the server, and does so by uploading encrypted message logs and syncing the keys between clients. You can delete the logs later, or delete your keys, or even push fake logs if you want. It's still happening outside of the original encrypted session and the adversary can't confirm what actually was said in the original session.

I don't know why you think that PFS is broken if a local client has to be breached to recover encrypted data from a cloud backup, but PFS is not broken if a local client has to be breached to recover the same data from the client itself. Literally the only difference is where the data is stored, so either chat logs available to the client break PFS or they do not

Matrix does it this way

I run a cryptography forum, I know the exact definition of these terms. Message logs in plaintext is very distinct from forward secrecy. What forward secrecy means in particular is that captured network traffic can't be decrypted later even if you at a later point can steal the user's keys (because the session used session keys that were later deleted). Retrieving local logs with no means of verifying authenticity is nothing more than a classical security breach.

You can transfer messages as a part of an account transfer on Signal (at least on Android). This deactivates the app on the old device (so you can't do it silently to somebody's device)

There's already addons that can recognize in-video sponsored content and skip, if youtube splices in ads into the video stream these addons will still work (although depending on how strict server side logic is, they may have to pause when the buffer runs out until the time of the ad length has passed)

As long as the naming pattern is distinct from important domains you can still block it based on pattern matching. They need to obfuscate ad domains and other hosting domains the same way.

Creating subdomains is quite fast because the request goes right through when it's unknown to caches, it's updates when you reuse existing ones that causes trouble with lag.

Message logs doesn't break forward secrecy in a cryptographic sense, retaining original asymmetric decryption keys (or method to recreate them) does. Making history editable would help against that too.

What Signal actually intends is to limit privacy leaks, it only allows history transfer when you transfer the entire account to another device and "deactivate" the account on the first one, so you can't silently get access to all of somebody's history

You can still push old message history from your main device to your other devices, you can re-encrypt