
A microdot is text or an image substantially reduced in size to prevent detection by unintended recipients. Microdots are normally circular and around 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 the fact that the microdots have often been about the size and shape of a
typographical dot, such as a
period or the
tittle of a lowercase ''i'' or ''j''. Microdots are, fundamentally, a
steganographic approach to message protection.
History
In 1870 during the
Franco-Prussian War,
Paris
Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. ...
was under siege and messages were sent by
carrier pigeon
The homing pigeon, also called the mail pigeon or messenger pigeon, is a variety of domestic pigeons (''Columba livia domestica'') derived from the wild rock dove, selectively bred for its ability to find its way home over extremely long dist ...
. Parisian photographer
René Dagron
René Prudent Patrice Dagron (17 March 1817 – 13 June 1900) was a French photographer and inventor. He was born in Aillières-Beauvoir, Sarthe, France. used
microfilm
Microforms are scaled-down reproductions of documents, typically either films or paper, made for the purposes of transmission, storage, reading, and printing. Microform images are commonly reduced to about 4% or of the original document size. F ...
to permit each pigeon to carry a high volume of messages, as pigeons can carry little weight.
Improvement in technology since then has made even more miniaturization possible.
At the International Congress of Photography in Paris in 1925
Emanuel Goldberg
Emanuel Goldberg ( he, עמנואל גולדברג; yi, עמנואל גאָלדבערג; russian: Эмануэль Гольдберг) (born: 31 August 1881; died: 13 September 1970) was an Israeli physicist and inventor. He was born in Moscow a ...
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 a surface of 0.01 mm
2. 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.
A technique comparable to modern microdots for
steganographic purposes was first used in
Germany
Germany, officially the Federal Republic of Germany (FRG),, is a country in Central Europe. It is the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the sou ...
between
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
and
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. It was also later used by many countries to pass messages through insecure postal channels. Later microdot techniques used film with
aniline
Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile start ...
dye, rather than
silver halide
A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wi ...
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". However, there never was a Professor Zapp at that university and microdot historian William White has denounced Hoover's article as a "concoction of semitruths and overt disinformation".
Nevertheless, this article was reprinted, translated, and widely and uncritically cited in the literature on espionage. 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
Emanuel Goldberg ( he, עמנואל גולדברג; yi, עמנואל גאָלדבערג; russian: Эмануэль Гольдберг) (born: 31 August 1881; died: 13 September 1970) was an Israeli physicist and inventor. He was born in Moscow a ...
, who was a professor in Dresden, with Kurt Zapp who, late in the Second World War, was in Dresden and taught spies how to make microdots.
A World War II spy kit for microdot production was sometimes called a Zapp outfit.

In Germany after the
Berlin Wall was erected, special cameras were used to generate microdots which were then attached to letters and sent through the regular mail. These microdots often went unnoticed by inspectors, and information could be read by the intended recipient using a
microscope
A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisibl ...
.
Modern usage
Microdot identification
Microdot identification is a process where tiny identification tags are
etched or coded with a given number, or for use on vehicles, a vehicle
VIN
Vin or VIN may refer to:
Arts, entertainment, and media
* Vîn TV, a Kurdish language satellite television channel founded in 2007
* ''Vos Iz Neias?'', an American Jewish online news site
* Coastal radio station VIN Geraldton (callsign), a statio ...
, asset identification number or a unique
serial number. Unique
personal identification number
A personal identification number (PIN), or sometimes redundantly a PIN number or PIN code, is a numeric (sometimes alpha-numeric) passcode used in the process of authenticating a user accessing a system.
The PIN has been the key to facilitatin ...
s (PIN), asset identification number or customized customer data entries are also available. The microdots are brushed or sprayed onto the key parts of an asset to provide complete parts marking. The technology was developed in the United States in the 1990s before being commercialized by various manufacturers and distributors around the world.
In South Africa it is a legal requirement to have microdot fitted to all new vehicles sold since September 2012 and to all vehicles that require police clearance.
Most printers print in addition to the documents requested on the pages tiny
yellow dots containing printer serial number and time stamp.
These are not microdots, but arrays of difficult-to-see dots across the printed page in an encoded pattern.
Popular culture
* In the 2006 motion picture ''
Mission: Impossible III'' a microdot was hidden on the back of a postage stamp and contained a magnetically stored video file.
* In ''
Superman'' #655 (Vol. 1, Sep. 2006),
Clark Kent
Superman is a superhero who appears in American comic books published by DC Comics. The character was created by writer Jerry Siegel and artist Joe Shuster, and debuted in the comic book ''Action Comics'' #1 (cover-dated June 1938 and publi ...
uses various microdots implanted throughout a suspense novel to read not only the novel but also numerous other works on various topics. The microdots were used here to further explore Superman's newly enhanced mental capabilities.
* In the 1967 movie ''
You Only Live Twice'', Tiger tells
James Bond
The ''James Bond'' series focuses on a fictional Secret Intelligence Service, British Secret Service agent created in 1953 by writer Ian Fleming, who featured him in twelve novels and two short-story collections. Since Fleming's death in 19 ...
that his men found a microdot on a captured SPECTRE photograph, which he enlarges for Bond.
* In the 1966 movie ''
Arabesque
The arabesque is a form of artistic decoration consisting of "surface decorations based on rhythmic linear patterns of scrolling and interlacing foliage, tendrils" or plain lines, often combined with other elements. Another definition is "Foli ...
'' a microdot was hidden in the eye of a goose on a parchment of hieroglyphs.
* One of
Philip K. Dick
Philip Kindred Dick (December 16, 1928March 2, 1982), often referred to by his initials PKD, was an American science fiction writer. He wrote 44 novels and about 121 short stories, most of which appeared in science fiction magazines during his l ...
's characters in ''
A Scanner Darkly'' tells a drug-induced story wherein a worker at the local microdot factory had tracked the company's entire inventory out into the parking lot on the sole of his shoe.
* In the
Nancy Drew
Nancy Drew is a Fictional character, fictional character appearing in several Mystery fiction, mystery book series, movies, and a TV show as a teenage amateur sleuth. The books are ghostwriter, ghostwritten by a number of authors and published ...
PC game, ''
Phantom of Venice'', a clue is hidden using a microdot on an exclamation point.
* The 2003 film ''
Paycheck'' uses a very realistic rendering of a microdot as a key plot element. The handling of microdot technology in the film is worth noting as the viewer is shown both how well a microdot can be made to blend into a complementary environment as well as how much information such a dot can carry.
* In the ''
White Collar White collar may refer to:
* White-collar worker, a salaried professional or an educated worker who performs semi-professional office, administrative, and sales-coordination tasks, as opposed to a blue-collar worker, whose job requires manual labor ...
'' episode "As You Were" a microdot was used to send a covert message to Special Agent
Clinton Jones.
* In the ''
Covert Affairs'' episode "Sad Professor" a microdot was used by one of the characters to store intelligence related to an operation that a language professor used who previously worked for the
CIA.
*In ''
The Venture Bros.'' episode
"Powerless In the Face of Death"; while in prison, the character
Tiny Joseph comments that "they don't usually write microdots by hand."
* In ''
C.I.D.'' Episodes 201 and 202, "Case of the Multiple Puzzles", a microdot was sold by an Intelligence Bureau officer to terrorists. The microdot had information about missile technology of India.
*
Lee Harvey Oswald
Lee Harvey Oswald (October 18, 1939 – November 24, 1963) was a U.S. Marine veteran who assassinated John F. Kennedy, the 35th president of the United States, on November 22, 1963.
Oswald was placed in juvenile detention at the age of 12 ...
famously wrote "micro dots" in his address book underneath the address for a printing company he worked for in 1962 and 1963.
[http://issuu.com/ajweberman/docs/1adressbookcolor/24?e=0/10629136 p.24 of Address Book]
* In the 1965 television series ''
Get Smart
''Get Smart'' is an American comedy television series parodying the secret agent genre that had become widely popular in the first half of the 1960s, with the release of the '' James Bond'' films. It was created by Mel Brooks and Buck Henry, ...
'' (Season 1, Episode 21 - "Dear Diary" original air-date Feb 12, 1966) Agent 86 and Agent 99 are shown the first "microdot" in the Spy City Museum. The comedic value is in the microdot being the size of a small plate.
* In the 1968 television series
''It Takes a Thief'' (Season 1, Episode 8,
''A Spot Of Trouble''), Agent Mundy is called in when sensitive plans for a weapon are stolen and later learned have been converted to a microdot.
*In the
Blake & Mortimer ''
S.O.S. Meteors'' comic book, the foreign organization responsible for altering the weather patterns over Europe uses microdots embedded in letter envelopes to relay projected weather data to their clandestine stations. The microdot is however misattributed to "famous German inventor" Zapp.
* In the television series ''
The Avengers
Avenger, Avengers, The Avenger, or The Avengers may refer to:
Arts and entertainment In the Marvel Comics universe
* Avengers (comics), a team of superheroes
** Avengers (Marvel Cinematic Universe), a central team of protagonist superheroes o ...
'', the 1961 episode "One for the Mortuary"
has microdots and their transport as a major plot theme.
* In
Margaret Atwood
Margaret Eleanor Atwood (born November 18, 1939) is a Canadian poet, novelist, literary critic, essayist, teacher, environmental activist, and inventor. Since 1961, she has published 18 books of poetry, 18 novels, 11 books of non-fiction, ...
's 2019 novel ''
The Testaments'', the sequel to ''
The Handmaid's Tale
''The Handmaid's Tale'' is a futuristic dystopian novel by Canadian author Margaret Atwood and published in 1985. It is set in a near-future New England in a patriarchal, totalitarian theonomic state known as the Republic of Gilead, which ...
'', microdots are used for communication between a high official of The Republic of Gilead and Mayday resistance members in Canada. The microdots were smuggled back and forth in print brochures and also inserted into the tattoo of a defector from Gilead to Canada.
* In ''
The Blacklist'', episode 12 of season 7 “Cornelius Ruck (No. 155),” a CIA operative uses microdot to covertly send a list of operatives back to the US.
See also
*
Photolithography
In integrated circuit manufacturing, photolithography or optical lithography is a general term used for techniques that use light to produce minutely patterned thin films of suitable materials over a substrate, such as a silicon wafer (electroni ...
References
External links
Microdot photographyAnti Theft Microdot technology in INDIA
{{Espionage
Steganography