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m (New page: ''Archived past selected research articles'' <small>2008-July-5</small> <bibtex> @article{ publisher="Taylor & Francis", journal="Journal of Digital Forensic Practice", author="Y...)
 
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''Archived past selected research articles''
  
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<small>2008-July-5</small>
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<bibtex>
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@article{
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  publisher="Taylor & Francis",
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  journal="Journal of Digital Forensic Practice", 
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  author="Yoginder Singh Dandass and Nathan Joseph Necaise and Sherry Reede Thomas",
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  title="An Empirical Analysis of Disk Sector Hashes for Data Carving",
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  year=2008,
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  volume=2,
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  issue=2,
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  pages="95--106",
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  abstract="Discovering known illicit material on digital storage devices is an important component of a digital forensic investigation. Using existing data carving techniques and tools, it is typically difficult to recover remaining fragments of deleted illicit files whose file system metadata and file headers have been overwritten by newer files. In such cases, a sector-based scan can be used to locate those sectors whose content matches those of sectors from known illicit files. However, brute-force sector-by-sector comparison is prohibitive in terms of time required. Techniques that compute and compare hash-based signatures of sectors in order to filter out those sectors that do not produce the same signatures as sectors from known illicit files are required for accelerating the process.
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This article reports the results of a case study in which the hashes for over 528 million sectors extracted from over 433,000 files of different types were analyzed. The hashes were computed using SHA1, MD5, CRC64, and CRC32 algorithms and hash collisions of sectors from JPEG and WAV files to other sectors were recorded. The analysis of the results shows that although MD5 and SHA1 produce no false-positive indications, the occurrence of false positives is relatively low for CRC32 and especially CRC64. Furthermore, the CRC-based algorithms produce considerably smaller hashes than SHA1 and MD5, thereby requiring smaller storage capacities. CRC64 provides a good compromise between number of collisions and storage capacity required for practical implementations of sector-scanning forensic tools.",
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  url="http://www.informaworld.com/10.1080/15567280802050436"
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}
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</bibtex>
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Authors Dandass ''et. al'' analyzed 528 million sectors from 433,630 unique files. They computed the CRC32, CRC64, MD5 and SHA-1 of each sector. Not surprisingly, they find that the MD5 and SHA-1s of the sectors are different if the sectors are different. They find 94 CRC64 collisions and 30 million CRC32 collisions. The conclusion is that, if you are search for a single sector or building a database of single sector hashes, you are better off building a database of CRC64s because they are easier to store and dramatically faster to calculate than the traditional hash functions, and they are nearly as accurate.

Revision as of 15:34, 12 July 2008

Archived past selected research articles

2008-July-5

Yoginder Singh Dandass, Nathan Joseph Necaise, Sherry Reede Thomas - An Empirical Analysis of Disk Sector Hashes for Data Carving
Journal of Digital Forensic Practice 2:95--106,2008
http://www.informaworld.com/10.1080/15567280802050436
Bibtex
Author : Yoginder Singh Dandass, Nathan Joseph Necaise, Sherry Reede Thomas
Title : An Empirical Analysis of Disk Sector Hashes for Data Carving
In : Journal of Digital Forensic Practice -
Address :
Date : 2008

Authors Dandass et. al analyzed 528 million sectors from 433,630 unique files. They computed the CRC32, CRC64, MD5 and SHA-1 of each sector. Not surprisingly, they find that the MD5 and SHA-1s of the sectors are different if the sectors are different. They find 94 CRC64 collisions and 30 million CRC32 collisions. The conclusion is that, if you are search for a single sector or building a database of single sector hashes, you are better off building a database of CRC64s because they are easier to store and dramatically faster to calculate than the traditional hash functions, and they are nearly as accurate.

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