this post was submitted on 24 Aug 2024
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Encryption and compression don't play well together though. You should consider that when storing sensitive files. That's why it's recommended to leave compression off in https because it weakens the encryption strength
How does that work? Encryption should not care at all about the data that is being encrypted. It is all just bytes at the end of the day, should not matter if they are compressed or not.
Disabling compression in HTTPS is advised to prevent specific attacks, but this is not about compression weakening encryption directly. Instead, it’s about preventing scenarios where compression could be exploited to compromise security. The compression attack is used to leak information about the content of the encrypted data, and is specific to HTTP, probably because HTTP has a fixed or guessable structure.
Looks to be an exploit only possible because compression changes the length of the response and the data can be injected into the request and is reflected in the response. So an attacker can guess the secret byte by byte by observing a shorter response form the server.
That seems like something not feasible to do to a storage device or anything that is encrypted at rest as it requires a server actively encrypting data the attacker has given it.
We should be careful of seeing a problem in one very specific place and then trying to apply the same logic to everything broadly.
It is only in TLS where you have to disable compression, not in HTTP.
https://security.stackexchange.com/questions/19911/crime-how-to-beat-the-beast-successor/19914#19914
Could you explain how a CRIME attack can be done to a disk?
There is also the BREACH which targets gzip/deflate compression on http as well. But also, don't see how that affects disk encryption.
I can't explain, perhaps due to my limited knowledge about the subject. I understood that compression was a weakening factor for encryption years ago when I heard about it. Always good to do your own research in the end 🙃