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Date: Tue, 10 Feb 2015 15:07:24 +0100
From: Sylvain Pelissier <>
Subject: eCryptfs key wrapping help to crack user password


I have noticed that ecryptfs-utils is the default program used by the
Ubuntu distributions for home folder encryption since version 10.04.
In this case, a wrapping key is generated from the user password
using the hash function SHA-512 applied 65536 times. By default, the
wrapping key is hashed with the default fixed salt
(0x0011223344556677) and stored in the a file.
This was already noticed in bug :
For  Ubuntu installations time-memory trade-off (rainbow tables, etc.)
can apply, as well as bulk dictionary attacks to crack user passwords
of Ubuntu installations when the home folder encryption is activated.
I am currently working to correct this weakness.

Sylvain Pelissier

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