Editing Paper shredder (section)

==Unshredding and forensics==<!-- This section is linked from [[Stasi]] -->
[[File:Shredded 1979-09-01 1305Z CIA cable from American Embassy Tehran.jpg|thumb|An example of a shredded and reassembled document during the [[Iran hostage crisis]]]]

For paper shredders to achieve their purpose, it should not be possible to reassemble and read shredded documents. In practice, this depends on how well the shredding has been done, and the resources put into reconstruction. The amount of effort put into reconstruction often depends on the importance of the document, e.g. whether it is a simple personal matter, [[corporate espionage]], a criminal matter, or a matter of [[national security]].

The difficulty of reconstruction can depend on the size and legibility of the text, whether the document is single- or double-sided, the size and shape of the shredded pieces, the orientation of the material when fed, how effectively the shredded material is further randomized afterwards, and whether other processes such as pulping and chemical decomposition are used. Even without a full reconstruction, in some cases useful information can be obtained by forensic analysis of the paper, ink, and cutting method.

===Reconstruction examples===
{{Wikisource|Portal:Documents seized from the U.S. Embassy in Tehran/Shredded Documents}}

*After the [[Iranian Revolution]] and the takeover of the U.S. embassy in [[Tehran]] in 1979, Iranians enlisted local carpet weavers who reconstructed the pieces by hand. The recovered documents would be later released by the Iranian government in a series of books called "Documents from the US espionage Den".<ref>{{cite book |author= Dānishjūyān-i Musalmān-i Payraw-i Khaṭṭ-i Imām, Dānishjūyan-i Musalmān-i Payraw-i Khaṭṭ-i Imām |title= Documents from the U.S. Espionage Den |publisher= Published by Muslim Students Following the Line of the Iman |year= 1980 |url= https://archive.org/details/DocumentsFromTheU.s.EspionageDen |url-status= live |archive-url= https://web.archive.org/web/20131018143837/https://archive.org/details/DocumentsFromTheU.s.EspionageDen |archive-date= 2013-10-18 }}</ref> The US government subsequently improved its shredding techniques by adding pulverizing, pulping, and chemical decomposition protocols.
*Modern computer technology considerably speeds up the process of reassembling shredded documents. The strips are scanned on both sides, and then a computer determines how the strips should be put together. Robert Johnson of the National Association for Information Destruction<ref>{{cite web|url=https://naidonline.org/|title=National Association for Information Destruction|work=naidonline.org|url-status=live|archive-url=https://web.archive.org/web/20090805065828/http://www.naidonline.org/|archive-date=2009-08-05}}</ref> has stated that there is a huge demand for document reconstruction. Several companies offer commercial document reconstruction services. For maximum security, documents should be shredded so that the words of the document go through the shredder horizontally (i.e. perpendicular to the blades). Many of the documents in the [[Enron scandal|Enron Accounting scandals]] were fed through the shredder the wrong way, making them easier to reassemble.
*In 2003, there was an effort underway to recover the shredded archives of the [[Stasi]], the East German secret police.<ref>{{cite news |last= Heingartner |first= Douglas |title= Back Together Again |newspaper= New York Times |date= 2003-07-17 |url= https://www.nytimes.com/2003/07/17/technology/back-together-again.html |access-date= 2007-01-03 |url-status= live |archive-url= https://web.archive.org/web/20080305141421/http://query.nytimes.com/gst/fullpage.html?res=9803E3D7123CF934A25754C0A9659C8B63 |archive-date= 2008-03-05}}</ref> There are "millions of shreds of paper that panicked Stasi officials threw into garbage bags during the regime's final days in the fall of 1989". As it took three dozen people six years to reconstruct 300 of the 16,000 bags, the Fraunhofer-IPK institute has developed the ''Stasi-Schnipselmaschine'' ('Stasi snippet machine') for computerized reconstruction and is testing it in a pilot project.
*The [[DARPA Shredder Challenge 2011]] called upon computer scientists, puzzle enthusiasts, and anyone else with an interest in solving complex problems, to compete for up to $50,000 by piecing together a series of shredded documents. The Shredder Challenge consisted of five separate puzzles in which the number of documents, the document subject matter and the method of shredding were varied to present challenges of increasing difficulty. To complete each problem, participants were required to provide the answer to a puzzle embedded in the content of the reconstructed document. The overall prizewinner and prize awarded was dependent on the number and difficulty of the problems solved. [[DARPA]] declared a winner on December 2, 2011 (the winning entry was submitted 33 days after the challenge began) – the winner was "[[All your base are belong to us|All Your Shreds Are Belong To U.S.]]" using a combination system that used automated sorting to pick the best fragment combinations to be reviewed by humans.<ref>{{cite web |title=Darpa Shredder Challenge |url=http://archive.darpa.mil/shredderchallenge/ |website=Darpa.mil |publisher=U S. Department of Defense |access-date=27 September 2016|url-status=dead |archive-url=https://web.archive.org/web/20160825060146/http://archive.darpa.mil/shredderchallenge/ |archive-date=25 August 2016}}</ref>

===Forensic identification===
The individual shredder that was used to destroy a given document may sometimes be of [[forensic]] interest. Shredders display certain device-specific characteristics, "[[fingerprint]]s", like the exact spacing of the blades, the degree and pattern of their wear. By closely examining the shredded material, the minute variations of size of the paper strips and the microscopic marks on their edges may be able to be linked to a specific machine.<ref>{{cite journal |author= Jack Brassil |title= Tracing the Source of a Shredded Document |publisher= [[Hewlett-Packard]] |date= 2002-08-02 |url= http://www.hpl.hp.com/techreports/2002/HPL-2002-215.pdf |access-date= 2007-01-03 |url-status= live |archive-url= https://web.archive.org/web/20061029090544/http://www.hpl.hp.com/techreports/2002/HPL-2002-215.pdf |archive-date= 2006-10-29 }}</ref> (cf. the [[typewriter#Forensic examination|forensic identification of typewriters]].)