<-- Back to The Ancient Greeks and Steganography

Unless your message does not need to be sent or delivered for quite some time, the methods that the ancient Greeks developed may not be the best way to communicate under the radar. By no means have these methods become obsolete; messages are still transported clandestinely in hidden compartments.

Invisible Ink:
The most widely used and readily available method of steganography is using invisible ink. This special ink disappears from sight after being written on the page and can only be revealed by another agent.

The simplest of invisible inks are basic organic compounds that are unseen at room temperature, but will reveal a secret message when heated. Lemon juice and vinegar are the most used. In the past when spies have been unable to send messages using conventional invisible ink, they have used urine as a substitute.

Writing in bleach is another means of concealing a message. While nothing is seen normally, place a message written in bleach under ultraviolet light to reveal the message.

There are also more complex inks that can only be revealed with a specific chemical compound.

To avoid detection the sender would write the hidden message on the same sheet of paper as something else, such as a postcard or letter. After all mailing a black piece of paper would look rather suspicious. When the inconspicuous letter is received the message is then revealed by the other end without anyone knowing the wiser.

Use of Dots:
In Victorian England sending encrypted messages became very fashionable. Because it was cheaper to take out a classified ad in the newspaper and the conservative society considered most interaction between the sexes, lovers needed to find another way to communicate with each other without use of letters.

Their solution was a section in newspapers called "agony columns" where infatuated lovers would send encrypted messages to each other right in plain view.

Assuming that no one could crack the lovers' code, they were free to communicate without anyone knowing. Unfortunately many of England's premier cryptologists had the hobby of cracking lovers' messages and responding with their own commentary on the relationships.

What Victorian England did produce, other then a means for mathematical intellectuals to entertain themselves, was a method to hide messages right in the view of the public without anyone knowing.

To conceal a message, it would be printed hidden among the normal stories of a newspaper or periodical. A dot was placed under each letter of the message to hide the message. When the receiver wrote down each letter in order and put it all together it would reveal the message.

This method was effective because it made the message easily accessible to the recipient, but the public was totally unaware. Unless you knew there was a hidden message, the dots would only appear as ink splatters made by the printing press.

Microdots:
If you've ever seen the James Bond movie You Only Live Twice, or any Cold War spy film then you've probably seen a microdot. Microdots applied modern technology to the age old art of steganography.

First developed during World War II, microdots were created as a means of concealing vast amounts information without anyone seeing - literally. To the naked eye a microdot is almost completely invisible.

Mark IV microdot camera

The method for creating a microdot includes taking writing down the message and photographically shrinking it down to an almost invisible size. Most microdots are roughly the size of a pinhead. Without a microscope and knowledge of the exact location of the dot, microdots are almost impossible to find.

The only problem with microdots is that since they are photographically reduced separate from the paper they are attached to they must be physically applied to the cover document. The glue and glossy photo paper produce a glare when held at an angle to the light. Although very hard to do, a microdot can be discovered using this method.