[dm-crypt] Note: Characters inadvisable in Passphrases

Arno Wagner arno at wagner.name
Sat Jul 9 00:34:41 CEST 2011

On Sat, Jul 09, 2011 at 12:05:11AM +0200, Milan Broz wrote:
> On 07/08/2011 11:11 PM, Arno Wagner wrote:
> > So it is highly advisable to stay within the 94 printable 
> > characters on the standard, 128 character ASCII table. The
> > table can e.g. be found here: http://en.wikipedia.org/wiki/ASCII
> These suggestions also highly depends on environment (e.g. keyboard map).

Not so bad, since then you can still put the passphrase into a file 
using a hex-editor and read it from there if you stay in ASCII 7 Bit. 
If you do not know the original encoding, that can be a problem
or at least take a lot of experimenting. 
> (An example of local problem is if using Czech/English keyboard switch
> ("password1234 is not password+??????") or with qwerty/qwertz layout
> and suggestions like "try to not use y/z in passphrase to avoid the problem".
> Another common problem is  "please check that you have NumLock
> switched on when entering digits".
> Of course, 5 of 4 admins likes late night calls from users crying
> "my password doesn't work!"... :-)


> That said, there is no limitation in cryptsetup or dmcrypt regarding
> input character set.
> All these suggestions are quite generic and are intended to prevent
> problem with different environments (locales, keyboard layout etc).
> (My suggestion is better use longer non-dictionary ascii-friendly 
> passphrase than using non-ascii characters in it. But if you 
> disagree, just ignore this suggestion - it will work.... until 
> you need to unlock external drive on system with foreign keyboard 
> and locales... :-)

I completely agree. :-)

Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier 

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