Difference between pages "Linux Unified Key Setup (LUKS)" and "SuperFetch"

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Linux Unified Key Setup (LUKS) is commonly used by Linux to encrypt storage media volumes. LUKS is implemented in the Linux kernel in dm-crypt (dm = Device Mapper) and the user-space component cryptsetup.
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SuperFetch is a performance enhancement introduced in [[Microsoft]] [[Windows|Windows Vista]] to reduce the time necessary to launch applications. SuperFetch works with the memory manager service in Windows to analyze memory usage patterns over time to determine the optimal memory content for a given user for a date or time of day. This differs from the [[Prefetch]] technique used in Microsoft Windows XP, which preloads data into memory without analyzing usage patterns.
  
LUKS supports various encryption methods, like:
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From [http://msdn.microsoft.com/en-us/library/windows/hardware/dn653317(v=vs.85).aspx]: SuperFetch prioritizes the following kinds of pages to remain in memory:
* ARC4
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* Pages of applications that are used most frequently overall.
* [[AES]]
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* Pages of applications that are commonly used when resuming:
* [[Anubis]]
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** After extensive hibernation (for example, first thing in the morning).
* [[Blowfish|BlowFish]]
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** After shorter periods of sleep or hibernation (for example, after lunch).
* [[Cast5]]
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* [[Cast6]]
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* [[Serpent]]
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* Tnepres a reversed variant of [[Serpent]]
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* [[Twofish|TwoFish]]
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These encryption methods can be used in various chaining modes and with various initialization vector modes.
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If SuperFetch detects that the system drive is a fast solid-state drive (SSD) (as measured by Windows Experience Index Disk score), then SuperFetch turns off [[ReadyBoot]].
  
== How to detect ==
 
A LUKS encrypted volume starts with the "LUKS\xba\xbe" signature.
 
  
A hexdump of the start of the volume should look similar to:
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== Configuration ==
<pre>
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00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|
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00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
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00000020  00 00 00 00 00 00 00 00  63 62 63 2d 65 73 73 69  |........cbc-essi|
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00000030  76 3a 73 68 61 32 35 36  00 00 00 00 00 00 00 00  |v:sha256........|
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00000040  00 00 00 00 00 00 00 00  72 69 70 65 6d 64 31 36  |........ripemd16|
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00000050  30 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |0...............|
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</pre>
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The encryption method in the example is:
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Because SuperFetch appears to leave a system with no available memory, some users turn it off to create the appearance of having more free memory. The feature can be configured by changing the <tt>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters\EnableSuperfetch</tt> [[Registry]] key [http://www.codinghorror.com/blog/archives/000688.html]. A value of zero disables SuperFetch, one enables it for booting only, two for applications, and three for both applications and boot. This setting can also be changed using the Services console, <tt>services.msc</tt> [http://tiredblogger.wordpress.com/2007/03/27/superfetch-not-so-super-for-gaming/].
<pre>
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aes
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</pre>
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The encryption mode is in the format:
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== File Formats ==
<pre>
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chaining_mode[-initialization_vector_mode[:initialization_vector_options]]
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</pre>
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Which in the example is:
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Data for SuperFetch is gathered by the <tt>%SystemRoot%\System32\Sysmain.dll</tt>, part of the Service Host process, <tt>%SystemRoot%\System32\Svchost.exe</tt>, and stored in a series of files in the <tt>%SystemRoot%\Prefetch</tt> directory [http://www.microsoft.com/technet/technetmag/issues/2007/03/VistaKernel/]. These files appear to start with the prefix <tt>Ag</tt> and have a <tt>.db</tt> extension. The format of these files is not fully known, there is available unofficial partial specification [http://blog.rewolf.pl/blog/?p=214] and open source (GPL) dumper for .db files [http://code.google.com/p/rewolf-superfetch-dumper/]. Some information can be gleaned from these files by searching for [[Unicode]] [[strings]] in them.
<pre>
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cbc-essiv:sha256
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</pre>
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And the password hashing method in the example is:
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The SuperFetch feature is seeded with some basic usage patterns when the operating system is installed [http://channel9.msdn.com/showpost.aspx?postid=242429].
<pre>
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ripemd160
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== See Also ==
</pre>
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* [[Prefetch]]
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* [[ReadyBoost]]
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* [[ReadyBoot]]
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* [[Windows SuperFetch Format|SuperFetch Format]]
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* [[Windows]]
  
 
== External Links ==
 
== External Links ==
* [http://clemens.endorphin.org/nmihde/nmihde-A4-ds.pdf New Methods in Hard Disk Encryption], by Clemens Fruhwirth, July 18, 2005
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* [http://en.wikipedia.org/wiki/Windows_Vista_I/O_technologies#SuperFetch Wikipedia: Windows Vista I/O technologies - SuperFetch]
* [http://wiki.cryptsetup.googlecode.com/git/LUKS-standard/on-disk-format.pdf LUKS On-Disk Format Specification - Version 1.2.1], by Clemens Fruhwirth, October 16, 2011
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* [http://channel9.msdn.com/showpost.aspx?postid=242429 Channel 9 Interview with Michael Fortin of Microsoft on SuperFetch]
* [https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Security_Guide/sect-Security_Guide-LUKS_Disk_Encryption.html LUKS Disk Encryption], by [[RedHat]]
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* [http://www.informationweek.com/news/showArticle.jhtml?articleID=196902178 Microsoft Predicts The Future With Vista's SuperFetch] from Information Week
* [https://googledrive.com/host/0B3fBvzttpiiSNUVYSFF1TmRONmc/Linux%20Unified%20Key%20Setup%20(LUKS)%20Disk%20Encryption%20format.pdf LUKS Disk Encryption format specification], by the [[libluksde|libluksde project]], July 2013
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* [http://jessekornblum.com/presentations/dodcc08-2.pdf DC3 Presentation: My You Look SuperFetching], by Jesse Kornblum
* [http://www.jakoblell.com/blog/2013/12/22/practical-malleability-attack-against-cbc-encrypted-luks-partitions/ Practical malleability attack against CBC-Encrypted LUKS partitions], by Jakob Lell, December 22, 2013
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== Tools ==
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=== Open Source ===
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* [https://code.google.com/p/rewolf-superfetch-dumper/ rewolf-superfetch-dumper]
  
[[Category:Disk encryption]]
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[[Category:Windows]]
[[Category:Linux]]
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Revision as of 01:48, 24 April 2014

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Further information might be found on the discussion page.

SuperFetch is a performance enhancement introduced in Microsoft Windows Vista to reduce the time necessary to launch applications. SuperFetch works with the memory manager service in Windows to analyze memory usage patterns over time to determine the optimal memory content for a given user for a date or time of day. This differs from the Prefetch technique used in Microsoft Windows XP, which preloads data into memory without analyzing usage patterns.

From [1]: SuperFetch prioritizes the following kinds of pages to remain in memory:

  • Pages of applications that are used most frequently overall.
  • Pages of applications that are commonly used when resuming:
    • After extensive hibernation (for example, first thing in the morning).
    • After shorter periods of sleep or hibernation (for example, after lunch).

If SuperFetch detects that the system drive is a fast solid-state drive (SSD) (as measured by Windows Experience Index Disk score), then SuperFetch turns off ReadyBoot.


Contents

Configuration

Because SuperFetch appears to leave a system with no available memory, some users turn it off to create the appearance of having more free memory. The feature can be configured by changing the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters\EnableSuperfetch Registry key [2]. A value of zero disables SuperFetch, one enables it for booting only, two for applications, and three for both applications and boot. This setting can also be changed using the Services console, services.msc [3].

File Formats

Data for SuperFetch is gathered by the %SystemRoot%\System32\Sysmain.dll, part of the Service Host process, %SystemRoot%\System32\Svchost.exe, and stored in a series of files in the %SystemRoot%\Prefetch directory [4]. These files appear to start with the prefix Ag and have a .db extension. The format of these files is not fully known, there is available unofficial partial specification [5] and open source (GPL) dumper for .db files [6]. Some information can be gleaned from these files by searching for Unicode strings in them.

The SuperFetch feature is seeded with some basic usage patterns when the operating system is installed [7].

See Also

External Links

Tools

Open Source