[Cryptography] Can crypto implement OS/FS protections ?

Dave Horsfall dave at horsfall.org
Mon Nov 21 16:06:27 EST 2022

On Mon, 21 Nov 2022, Jerrold Leichter wrote:

> You can certainly control *read* access by encryption (though there are 
> limits to the protection - e.g., suppose I want to say that if you don’t 
> have read access to a file, you can’t even tell if it’s been changed 
> since you last looked).

Unless I've misunderstood you, under *Nix you don't need read access to a 
file to access its metadata (the inode); you merely need to be able to 
access it from its parent directly.  In the case above, you "stat" the 
file and examine "st_mtime".

For example, on my FreeBSD box (this one):

    aneurin% ls -l /etc/master.passwd 
    -rw-------  1 root  wheel  2785 Nov  3 15:07 /etc/master.passwd

I can't read it, but I can see that it was last changed on 3rd November.

-- Dave

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