Re: Question on ext4 directory hashes in combination with file name encryption

From	Theodore Ts'o <tytso@mit.edu>
Newsgroups	linux.kernel
Subject	Re: Question on ext4 directory hashes in combination with file name encryption
Date	2016-10-01 02:50 +0200
Message-ID	<sngF3-Vh-3@gated-at.bofh.it> (permalink)
References	<sn6FI-2MJ-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, Sep 30, 2016 at 04:09:09PM +0200, Richard Weinberger wrote:
> 
> if I read the ext4 code correctly, you pass encrypted filenames to ext4fs_dirhash().
> These filenames are not encoded and therefore binary gibberish.

That's correct.

> Isn't this a problem for the ext4 hash functions? My fear is that these hashes are optimized
> for ASCII strings and produce more collisions when binary data is used as input.

I'm not particularly worried.  In general, while the converse is true;
that hashes that assume that they are used for binary data might not
work as well for ASCII strings, the ext4 hash functions should work
fine for binary data.

					- Ted

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Question on ext4 directory hashes in combination with file name  encryption Richard Weinberger <richard@nod.at> - 2016-09-30 16:10 +0200
  Re: Question on ext4 directory hashes in combination with file name encryption Andreas Dilger <adilger@dilger.ca> - 2016-09-30 22:30 +0200
  Re: Question on ext4 directory hashes in combination with file name  encryption Theodore Ts'o <tytso@mit.edu> - 2016-10-01 02:50 +0200

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