Invisible ink , also known as security ink , is a writing substance that does not look good on the app or shortly thereafter, and can later be made visible in several ways. Invisible ink is one form of steganography.
Video Invisible ink
Histori
One of the earliest writers who mentions invisible ink is Aeneas Tacticus, in the 4th century BC. He mentions it in discussing how to survive under siege, but does not indicate the type of ink to be used. Philo of Byzantium is probably the first author known to describe invisible inks using reagents around 280-220 BC, with galls of oak and vitriol. These ingredients are used to make gall bladder inks. People soon discover that they can write invisibly with one material and then cause the writing to appear by adding another. Pliny the Elder and Roman poet Ovid advise on the use of plant and milk juices to write secret messages. Lemon is also used as organic ink by Arabs around 600 CE, and during the 16th century in Europe.
Giovanni Battista della Porta is credited with the first recipe for sympathetic ink, derived from alum and vinegar, as well as the first book on secret writing and invisible ink, Magia Naturalis (1558, 1589). Since then, a variety of invisible inks have been used for all sorts of secret purposes. A formula similar to the oak bile ink created by John Jay and used by George Washington and the Culper Spy Ring during the American Revolution and lemon juice was used by Spies Lemon Juice during World War I.
Maps Invisible ink
General apps and usage
Invisible ink can be applied to the writing surface with a stylus, stamp, pen, toothpick, calligraphy pen, or even a finger dipped in a liquid. Once dry, the written surface looks as if it is empty, with the same texture and reflectivity as the surrounding surface.
Inks can be made and then seen by different methods according to the invisible ink type used. The ink may be exposed by heat or by appropriate chemical applications, or may be made visible by looking under ultraviolet light. Inks developed by chemical reactions can depend on acid-base reactions (such as litmus paper), reactions similar to blueprints, or hundreds of others. The developer fluid can be applied using a spray bottle, but some developers are in the form of steam, eg. ammonia vapor is used to develop phenolphthalein inks.
There is also an invisible ink pen that has two tips - one tip for writing invisible ink, and another tip for developing ink. Invisible ink is sometimes used to print parts of pictures or text in books for children to play, always including a "pen decoder" used to show parts of text or images that are not visible, thus expressing the answer to the question which is printed in ordinary ink or completes the missing part of the image.
UV markers or markers with fluorescent inks that glow when illuminated with UV light are often used to mark valuable household items not seen in robbery cases. There are mainly security makers who are formulated to write on non-porous surfaces such as glass, plastic, metal, etc. The inks that have been used and then can be identified using black light or other UV light sources. Security markers can be obtained commercially and are widely used as crime prevention.
Some commercially invisible inks shine very brightly, in different colors, under UV light. This makes them suitable for use in re-registration such as hand stamping.
There are some types of invisible ink that can only be invisible when applied to certain types of surfaces, but still visible to others.
Some vendors now offer invisible ink for use in computer inkjet printers. Such ink is usually seen under ultraviolet light. Common uses include printing information on business forms for use by form processors, without screwing up the visible content of the form. For example, some US Postal Mail sorting stations use UV-visible inks to print bar codes on envelopes sent that provide routing information for use by mail handling equipment farther down before delivery.
Very rarely, invisible ink has been used in art. Usually developed, though not always. There are artists who use joint effects with ink and invisible reactive paint and others to create effects when used in conjunction with UV lamps.
The E2E voting system called Scantegrity II uses invisible ink to allow voters to get a confirmation code only for the selected selection.
Properties of invisible "ideal" inks
What the "invisible" ink is invisible depends on the purpose of its use. For example, property tagging should ideally be done with ink easily readable under ultraviolet light, whereas in such ink espionage would be considered too easily detectable since a large number of letters can be rotated relatively quickly using UV light.
Invisible ink is essentially "unsafe" to a well-defined and well-equipped inspector, which must be matched by logistical difficulties in mass filtering of postal mail. It is easier to undertake large-scale undetectable screening of millions of electronic communications, than to mass filter even a small portion of conventional letters. In addition to the dictatorship in which a large number of personnel are employed to spy on compatriots, postal mail filtering is possible only in certain situations, such as letters to and from certain suspects or facilities.
The British SOE training manual used in the Second World War identifies the following properties of the "invisible" invisible ink:
- Mixed with water.
- Non-volatile, ie no prominent odor.
- Not storing crystals on paper, it's not easy to see in a glance.
- Not visible under ultraviolet light.
- Does not parse or blacken the paper eg. silver nitrate.
- Off with iodine, or with other casual developers.
- Potential developers for ink should be as little as possible.
- It should not develop under heat.
- Easily obtainable and have at least one possible use of the innocent by the holder.
- Not a compound of some chemicals, because this would violate No. 7.
From practical experience "6" and "9" are usually not appropriate. SOE agents are trained not to risk their lives through dependence on unsafe inks, mostly from World War I. In general, SOEs use invisible ink as a back-up method of communication when other more secure communication techniques are not available. The agency is known to supply special inks to its field agents, rather than having them rely on improvisation of the everyday chemicals that can be obtained. When agents are forced to improvise, they are advised to dilute the invisible ink as much as possible to reduce the likelihood of detection.
Scanning letters for secret messages
Invisible inks can be made visible to a fairly determined person, but the limitations are generally the time available and the fact that one can not apply the hours of effort to each piece of paper. Thus, successful use of invisible inks depends on not raising the suspicion that invisible ink may be present.
Ink marks that are not visible, such as pen scratches from sharp pens, coarseness, or paper reflective changes (duller or more shiny, usually from using non-reconstituted ink), can become apparent to careful observers who only use strong light, magnifying glass and nose. Also, key words in visible letters, such as "hot" or other strange code names, outside the context of places can alert the sensor to the presence of invisible ink. Invisible ink is ineffective with glossy or very fine paper types, since the size of these papers prevents the ink from being absorbed deep into paper and easily visible, especially if the paper is examined under a glancing light. However, there is commercially available ink for non-porous surfaces that are only visible under ultraviolet light and vice versa hardly seen on such surfaces.
Using ultraviolet light or iodine acid cabinets, messages can be quickly filtered for invisible ink and also read without first permanently developing invisible ink. So, if the sensor uses this method to intercept the message, the letter can then be sent to the intended recipient, who will be unaware that the secret message has been intercepted by a third party.
A "screening station" can theoretically involve visual inspection and smell, examination under ultraviolet light and then warming up all objects in the oven before finally attempting exposure to iodine fumes to produce optimum security in optimal time.
Ink type not visible
For practical reasons, ink is listed here according to the method of development. However, it should be understood that some inks - especially those that come from organic or composed of a mixture of some chemicals - can be made visible by several methods. For example, writing that is not visible with soapy water can be made to look good by heat, reaction with phenolphthalein, look under ultraviolet light, or by placing the page inside the iodine acid cabinet.
Ink developed by heat
Some of these are organic substances that oxidize when heated, which usually turns them into brown. For this type of "fixed heat" ink, any acid solution will work. The safest way to use any of the following substances for invisible ink is by dilution, usually with water, near the point when they become difficult to develop.
- Cola drink
- Honey solution, sugar solution (sugar turns into caramel through dehydration)
- Lemon juice, apples, oranges or onions (organic acids and paper form ester under heat)
- Milk (lactose dehydration)
- Body fluids are like blood serums.
- Soap water (carboxylate partially oxidizes)
- Wine, or vinegar
- Cobalt chloride, which turns blue when heated and becomes invisible after a while (if it does not overheat)
His writing is seen by heating the paper, either on the radiator, by ironing, using a hair dryer, or by placing it in the oven. The 100 watt bulb tends not to damage the paper.
Ink developed by chemical reactions
In many cases, the substance changes color when mixed with acid or base.
- Phenolphthalein, commonly used as a pH indicator, turns pink in the presence of a base such as ammonia or sodium carbonate.
- Vinegar, revealed by red cabbage water. Vinegar contains acetic acid that affects the pH indicator in red cabbage water. Vinegar can also be developed with heat, as above.
- Ammonia, developed by red cabbage water.
- Copper sulfate, developed by sodium iodide, sodium carbonate, ammonium hydroxide or potassium ferricyanide.
- Lead (II) nitrate, developed by sodium iodide.
- Iron (II) sulfate, developed by sodium carbonate or potassium ferricyanate.
- Cobalt (II) chloride, developed by potassium ferricyanide.
- Iron (III) sulfate, developed by sodium sulphide.
- Starch, developed by an iodine solution that changes the dark blue starch and light blue of the paper.
- Lemon juice, developed by iodine solution (ink turns white, paper turns light blue).
- Sodium chloride (common table salt), developed by silver nitrate.
- Cerium oxalate is developed by manganese sulfate and hydrogen peroxide
Ink visible under ultraviolet light
Some ink glows faintly (fluoresces) when under ultraviolet light. This is the property of many substances, especially organic substances and body fluids.
Other inks work in a way that is almost opposite to absorbing ultraviolet light but without fluorescence. When used on fluorescent paper, the inked areas are less fluorescent than the surrounding paper area when under ultraviolet light. It mainly belongs to yellow ink.
Some UV-visible inks can be detected on photocopying, because of the relatively strong ultraviolet component in the light of the photocopy scanner head.
Examples of ink expressed by ultraviolet light are:
- Laundry detergent contains optical brighteners
- Soaps
- Body fluids, serum, saliva
- Sunscreen
- lemon juice
Inks that change the paper surface
This includes almost any invisible ink, but pure distilled water can also be used in this way. Any liquid application will change the paper surface fiber or size.
Smoke made from iodine crystalline heating will develop the writing, which will look brown as iodine attaches preferentially to the changing areas of paper. Exposing paper to strong sunlight will return the writing to an invisible state, such as using a bleach solution.
Slightly muffling the paper with a sponge or with steam and then drying it before writing a message will prevent the writing from being developed by this method, but too much muffling will result in a sign paper shell.
Ink that disappears
The visible ink for a period of time with no intention made visible again is called the ink disappears. The disappearing ink usually relies on a chemical reaction between thymolphthalein and a basic substance such as sodium hydroxide. Thymolphthalein, which is usually colorless, is blue in solution with a base. Because the base reacts with carbon dioxide (always in the air), the pH falls below 10.5 and the color disappears. Pen is now also available which can be removed only by swiping a special pen over the original text. The disappeared ink has been used in gag squirtgun, for limited time secret messages, for security reasons on non-reusable cards, for fraudulent purposes, and for the manufacture of other clothing and handicrafts where measurement marks are required to disappear.
The modern usage
As an indication of security, most of the ink mentioned above was known at the end of World War I. However, in 1999, the US Central Intelligence Agency successfully requested that invisible ink of World War I remain excluded from mandatory declassification, based on the claim that invisible ink still relevant to national security. World War I documents remain classified until 2011.
Former MI-6 agent Richard Tomlinson alleged that the Rollerball pen rollers were extensively used by MI-6 agents to produce secret writing in the form of an invisible message while on a mission.
In 2002, a gang was charged for spreading riots between federal penitentiaries using coded phone messages, and ink messages that were not seen.
References
External links
- Secret Writing - CIA Freedom of Information Act (FOIA) Electronic Reading Room
Source of the article : Wikipedia
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