Editing Microdot

{{Short description|Steganograph method of hiding messages}}
{{other uses}}
[[File:German microdots World War II Mexico Spain.jpg|thumb|NSA photo of microdots taped inside the label of an envelope. The envelope was sent by [[Operation Bolívar|German spies in Mexico City]] to [[Lisbon]] during [[World War II]], but was intercepted by Allied intelligence.]]

A '''microdot''' is text or an image substantially reduced in size to prevent detection by unintended recipients. Microdots are normally circular and around {{convert|1|mm}} in diameter but can be made into different shapes and sizes and made from various materials such as polyester or metal. The name comes from microdots often having been about the size and shape of a [[typography|typographical]] dot, such as a [[full stop|period]] or the [[tittle]] of a lowercase ''i'' or ''j''. Microdots are, fundamentally, a [[steganography|steganographic]] approach to message protection.

== History ==
[[File:MicrodotCamera.jpg|thumb|Mark IV microdot camera]]
[[File:March 2020 Microdot Object (49673631061).jpg|thumb|A doll used by a German spy to smuggle microdot photographs to [[Nazi Germany]] until the spy's arrest in 1942. ([[FBI]] collection)]]

In 1870 during the [[Franco-Prussian War]], [[Paris]] was under siege and messages were sent by [[carrier pigeon]]. Parisian photographer [[René Dagron]] used [[microfilm]] to permit each pigeon to carry a high volume of messages, as pigeons can carry little weight.<ref>Kipper, Gregory. ''Investigator's Guide to Steganography''. Boca Raton: Auerbach Publications, 2003. {{ISBN?}}</ref>

Improvement in technology since then has made even smaller miniaturization possible.<ref>{{Cite book | last= Hayhurst | first=J. D. | title= The Pigeon Post into Paris 1870–1871 | publisher= (privately published) | year= 1970 | url= http://www.cix.co.uk/~mhayhurst/jdhayhurst/pigeon/pigeon.html}}</ref>

At the 1925 [[International Congress of Photography]] in Paris, [[Emanuel Goldberg]] presented a method of producing extreme reduction microdots using a two-stage process. First, an initial reduced negative was made, then the image of the negative was projected from the eyepiece of a modified microscope onto a collodium emulsion where the microscope specimen slide would be. The reduction was such that a page of text would be legibly reproduced in an area of 0.01&nbsp;mm<sup>2</sup>. This density is comparable to the entire text of the Bible fifty times over in one square inch. Goldberg's "Mikrat" (microdot) was prominently reported at the time in English, French and German publications.<ref name="Buckland 2006">{{Cite book | url= http://www.ischool.berkeley.edu/~buckland/goldberg.html | last= Buckland | first= Michael | title= Emanuel Goldberg and His Knowledge Machine: Information, Invention, and Political Forces | series= New Directions in Information Management | publisher= Libraries Unlimited | year= 2006}}</ref><ref>{{cite journal |last1=Goldberg |first1=Emanuel |title=A new process of micro-photography |journal=British Journal of Photography |date=13 August 1916|volume=73|issue=3458|pages=462–465}}</ref><ref>{{cite book |last1=Stevens |first1=G. W. W. |title=Microphotography: Photography and photofabrication at extreme resolution |date=1968 |publisher=Chapman & Hall |location=London |page=46 |edition=2 nd}}{{ISBN?}}</ref>

A technique comparable to modern microdots for [[steganography|steganographic]] purposes was first used in Germany during the [[Interwar period]]. It was also later used by many countries to pass messages through insecure postal channels. Later microdot techniques used film with [[aniline]] dye, rather than [[silver halide]] layers, as this was even harder for counter-espionage agents to find.

A popular article on espionage by [[J. Edgar Hoover]] in the ''Reader's Digest'' in 1946 attributed invention of microdots to "the famous Professor Zapp at the Technical University Dresden".<ref>{{cite journal |last1=Hoover |first1=J. Edgar |title=The enemy's masterpiece of espionage |journal=Reader's Digest |date=1946 |volume=48 |issue=April |pages=1–6 }}</ref> This article was reprinted, translated, and widely and uncritically cited in the literature on espionage. There never was a Professor Zapp at that university;<ref>{{cite book |last1=White |first1=William |title=The microdot: History and application |date=1992 |publisher=Phillips Publications |location=Williamstown, NJ |pages=49–56 | isbn= 0932572197}}</ref> Hoover's Zapp has been wrongly identified with [[Walter Zapp]], inventor of the [[Minox]] camera, which was used by spies but did not make microdots. Hoover appears to have conflated Emanuel Goldberg, who was a professor in Dresden, with Kurt Zapp who, late in [[World War II]], was in Dresden and taught spies how to make microdots.<ref name="Buckland 2006"/>

==Modern usage==
Microdot identification is a process in which tiny identification tags are [[etching|etched]] or coded with a unique [[serial number]] or, for use on vehicles, with a vehicle identification number ([[VIN]]) or asset identification number.<ref>{{cite web|url=http://southtahoenow.com/story/09/16/2015/high-tech-anti-theft-dots-help-south-lake-tahoe-police|title=High tech anti-theft dots to help South Lake Tahoe Police|website=South Tahoe Now|date=17 September 2015 |access-date=17 August 2018}}</ref><ref>{{cite web|url=http://www.dailydemocrat.com/article/NI/20150617/NEWS/150619902|title='Anti-Theft Dots' latest weapon against crime|date=12 August 2018|access-date=17 August 2018}}</ref><ref>{{cite web|url=http://www.local8now.com/home/headlines/Alcoa-Police-using-new-DNA-system-for-returning-stolen-property-330967012.html|title=Alcoa Police using new 'DNA' system for returning stolen property|first=Steven|last=Powell|access-date=17 August 2018}}</ref><ref>{{cite web|url=http://wtkr.com/2015/10/26/can-these-little-stickers-help-police-track-down-your-stolen-items/|title=Can these little stickers help police track down your stolen items?|date=26 October 2015|access-date=17 August 2018}}</ref><ref>{{cite web|url=http://www.alaskapublic.org/2015/11/27/north-pole-police-launch-new-anti-theft-program/|title=North Pole police launch new anti-theft program|first=Dan Bross, KUAC -|last=Fairbanks|date=28 November 2015|access-date=17 August 2018}}</ref> In South Africa it is a legal requirement to have a microdot fitted to all new vehicles sold since September 2012 and to all vehicles that require police clearance.<ref>{{Cite web|url=http://securityondots.com/microdot.html|title=Microdot Technology &#124;&#124; Security on Dots}}</ref>

Some printers print, in addition to the document contents requested, tiny [[yellow dots]] containing the printer serial number and a time stamp.<ref>{{cite web|url=https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots|title=List of Printers Which Do or Do Not Display Tracking Dots|date=19 September 2007|publisher=[[Electronic Frontier Foundation]]|access-date=2018-12-10}}</ref>

== See also ==
* [[Photolithography]]

== References ==
{{reflist}}

== External links ==
* [http://www.wonko.net/microdot2results.html Microdot photography]

{{Espionage}}

[[Category:Steganography]]
[[Category:Espionage techniques]]