Any sort of file system imprint would at least leave a trace that incognito had been used. I’m not sure how much of a problem at is, and how much of a trace it currently leaves.

What about swap space used on the disk by the OS, transparent to the application? Is that also a concern for “file system imprint”? What’s the threat model here? The application would have to use RAM that’s never swapped for storing this sort of information. That would make it quite heavy.

I think chrome devs want to limit the "file system imprint" as much as possible to enforce "no-history in incognito". There's been some discussions on finding a way around crash reporting in incognito session which stores the dump in the disk, and to my knowledge this is the only violation of this policy. [1]https://bugs.chromium.org/p/chromium/issues/detail?id=876270...

there are many mundane reasons to use incognito mode. and the system would work in a way that the user will not even know the decryption key since it can be generated on the fly for each session.

the browser could even encrypt all their data by default. (but for non-incognito mode with a known key) it could then write the normal and incognito data in such a way that you can't even see that there is incognito data in there if you don't have the incognito key

Initialising a fixed storage image with random data offers plausible deniability.

> thus giving you access to the disk securely

The amount of encrypted data could be a side channel