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London designer Matthew Plummer-Fernandez has developed a piece of software that allows users to visually corrupt 3D-print files so they can't be recognised on file-sharing sites.

Matthew Plummer-Fernandez's Disarming Corruptor algorithm can be used to transform and disguise STL (STereoLithography) files - which record the outer shape of an object to be printed - in a way that can be only reversed by trusted recipients with the relevant key.

"In a time of prolific online espionage, crackdowns on file-sharing, and a growing concern for the 3D-printing of illegal items and copyright-protected artefacts, Disarming Corruptor is a free software application that helps people to circumvent these issues," Plummer-Fernandez said, adding that the project was inspired by devices such as the Enigma Machine used to encrypt and decode messages during the Second World War.

Users open the file they want to distort, then use slide bars to set seven values that are displayed as an encryption key at the top of the screen. The last slider controls how much the form is corrupted, so the result can retain some recognisable elements or be totally obscured.

Pressing Corrupt transforms the shape according to these settings and saves the new file plus an image of the encryption key in the same location as the original. The disguised object can then be uploaded to a public file-sharing site like Thingiverse and the decoding key distributed to a few trusted people.

To restore the file to its original form, the recipient needs both the application and the unique seven-digit settings used by the sender. They simply open the corrupted version in the Disarming Corruptor program, move the sliders to generate the correct key in the top bar and click Repair.

Entering the incorrect settings to decode the file would just damage it further.

"When patent trolls and law enforcement agencies find these files on sharing sites they will only see abstract contortions, but within the trusting community these files will still represent the objects they are looking for, purposely in need of repair," he explained.

"It could also be used to symbolically decommission files and throw away the keys, or to make something inoperative yet still recognisable so that other users would have to request a key to put it into use," he continued.

The software is free and available for Mac OSX, and Plummer-Fernandez is working on exports for Linux and Windows.

Plummer-Fernandez was born in Colombia and now lives in London, where he graduated from the Royal College of Art's Design Products MA in 2009, and creates his own 3D-editing tools for design projects like the 3D-printed vessels made by scanning and manipulating everyday objects that he presented this time last year.

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