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Re: [opensuse-security] Encrypted Hard Drive

Hash: SHA1

The Monday 2007-09-24 at 20:14 -0700, Kai Ponte wrote:

> > > Can anyone say what level or form of encryption is used on the encrypted
> > > filesystems (ext3) under opensuse 10.2?
> >
> > The line in fstab for encrypted partitions (created by YaST) includes the
> > phrase
> >
> > encryption=twofish256
> >
> > There might be other choices, I'm not sure, but that is what YaST seemed to
> > default to.
> Thanks.
> That is what the Novell guys thought, too.

However, there are many more posibilities. The man page is hidden under 
"man losetup":

 -e encryption
        Enable  data  encryption.  Following   encryption
        types are recognized:

        NONE   Use no encryption (default).
        XOR    Use a simple XOR encryption.
        AES128 AES
               Use  128  bit  AES encryption. Password is
               hashed with SHA-256 by default.
        AES192 Use 192 bit AES  encryption.  Password  is
               hashed with SHA-384 by default.
        AES256 Use  256  bit  AES encryption. Password is
               hashed with SHA-512 by default.

        twofish128 twofish160 twofish192 twofish256
        blowfish128 blowfish160 blowfish192 blowfish256
        serpent128 serpent192 serpent256 mars128 mars192
        mars256 rc6-128 rc6-192 rc6-256 tripleDES
               These encryption types  are  available  if
               they  are  enabled in kernel configuration
               or corresponding modules have been  loaded
               to kernel.

Then there are more options of obscure effects:

 -S pseed
        Sets encryption  password  seed  pseed  which  is
        appended  to  user supplied password before hash-
        ing. Using different seeds for  different  parti-
        tions  makes  dictionary  attacks slower but does
        not prevent them if  user  supplied  password  is
        guessable. Seed is not used in multi-key mode.

Then, there is something named "multi-key mode", which is not explained. The
man page assumes you already knows the subject and you only need a refresher
- - which is not the case. :-(


     This document explains how to create encrypted file systems using the
   Cryptoloop functionality. Cryptoloop is part of the CryptoAPI in the 2.6
   Linux kernel series.
     This HOWTO describes how to use the Cryptoloop loop device encryption in
   the 2.6 Linux kernel series. Cryptoloop makes it possible to create encrypted
   file systems within a partition or another file in the file system. These
   encrypted files can the be moved to a CD, DVD, USB memory stick, etc.
   Cryptoloop makes use of the loop device. This device is a pseudo-device which
   serves as a "loop" through which each call to a the file system has to pass.
   This way, data can be processed in order to encrypt and decrypt it. Since
   kernel 2.6, the Crypto API has been integrated into the main kernel, and
   setting up an encrypted file system has become much easier. No additional
   kernel patches are required. An update of some userspace utilities is
   necessary. Unfortunately, the use of Cryptoloop is not very well-documented
   so far. This HOWTO is an attempt to make it easy everyone to create an
   encrypted file system using the standard Cryptoloop functionality. Cryptoloop
   is based on the Crypto API in the 2.6 Linux kernel. It should not be confused
   with Loop-AES, which is a completely separate project. Cryptoloop is similar
   to the Crypto API that was available as a separate patch for the 2.4 kernel
   series. The new version is not compatible with the older one.

Note from the 10.3 release notes:

   It is still possible to use cryptoloop via losetup and mount. Since we
   dropped the crude loop-AES patch from the util-linux package, some
   parameters for losetup (such as itercountk and pseed) no longer exist. If
   any of these settings are used in /etc/fstab the device is cannot be mounted
   directly any more. Migrate these settings to /etc/crypttab where boot.crypto
   contains the necessary compatability code.

   A method is described for encrypting a hard disk, either in whole or in part,
   with the encryption key stored on an external medium for increased security.

   (written for kernel 2.4)


     This document explains how to make your personal data secure by encrypting
   your Linux root filesystem using strong cryptography.

- -- 
       Carlos E. R.

Version: GnuPG v1.4.5 (GNU/Linux)
Comment: Made with pgp4pine 1.76


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