Signal and the Post Quantum World

I’d like to first start by saying I’m not a cryptographer. I’m not even a graduate. I just had this thought one day, and I’ve tried to do some research surrounding it to little avail.

As of today, we can be reasonably sure that the signal protocol is secure and private. No one except the intended recipient can read these messages. While individual messages are encrypted with AES256 (as of my knowledge), a lot of signal (and key distribution) relies on diffie-hellman key exchanges and asymmetric crpytography.

From what I’ve gathered, this makes it possible for a government that has stored all my traffic to decrypt and calculate my initial key with a quantum computer. Now, assuming that all packets in my country are monitored, would that mean that they are able to calculate all of my future symmetric keys (since part of the key creation uses diffie hellman)?

tl;dr: I’m not sure how quantum resistant signal is, assuming all my communications until now have been monitored

Post quantum cryptography is still very new, there has been a lot of progress though.