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Concealment device

This walnut shows that virtualy any type of domestic object can be converted into a concealment device, even food. It was used by the Secret Service of the USSR, the KGB, for a number of years to pass One-Time Pads (OTPs) to their secret agents operating under cover in Western Europe [1].
An OTP generally consists of a set of pages with random letters or numbers on them. They are used for coding end decoding secret messages that are truely unbreakable. As each OTP page can be used only once, and must be destroyed immediately after use, the agent needs to have sufficient supply of fresh OTP code material.

For a number of years, the KGB printed tiny little OTP books on very thin paper and used common objects like this walnut to hide them in. An agent could hide the walnut in his living room between real walnuts without arousing any suspicion.
Walnut concealment device with two OTP booklets

For this concealment, a real walnut was used that was nicely split at the centre and emptied. The OTP books generally consisted of pages with black and red text on them. The black printed pages were used for decoding a message, whilst the red printed ones were used for sending messages. Very thin paper was used so that it occupied less space and could be folded easily. The pages consisted of 5-digit groups, 10 rows x 6 columns per page, folded together as an harmonica.
The pages where then rolled-up and bound together by means of a piece of thread, and hidden inside the hollowed-out walnut. The two halves of the walnut were then rejoined and held by means of glue or a piece of gum. After that you could not tell them apart from a real walnut and the best place to 'hide' them was in plain sight, e.g. in a bowl between real waltnuts.

Each time the agent received or sent a message, he used at least one page of the OTP booklet, which he cut-off and burned after use, so that he could not be compromised by it later.
Two tiny OTP booklets

A walnut concealment like the one shown here was discovered during the 1980s in the home of a KGB agent in (then) West Germany [2]. After his arrest, the German Intelligence Agency (BND) 1 and the Criminal Police Office (BKA) 2 search his appartment. Initially nothing was found but then one of the officers decided to check the walnuts that were inconspicuously placed in a bowl on the table. Most of them appeared to be normal, but a couple of them weighted noticably less... Inside one of the walnuts they found two small OTP booklets, one for receiving messages (black) and one for sending them (red). Each booklet had multiple pages with 60 5-digit groups each.
  1. BND = Bundesnachrichtendienst, the German Intelligence Agency.
  2. BKA = Bundeskriminalamt, the German Federal Criminal Police Office.

Inconspicuous bowl with walnuts Opening the concealment OTP booklets hidden inside a real walnut Walnut concealment device with two OTP booklets Walnut concealment device with 2 OTP booklets Closed walnut concealment device: no cracks visible Opening the walnut concealment device Two tiny booklets compared to the size of a regular OTP booklet

The X-ray image below shows the bowl with the walnuts, with the organic parts in orange and green, and the non-organic booklet crearly sticking out in blue. Apart from using x-rays to find the concealment, it was also possible to identify it by its weight, as it is considerably lighter.

  1. Anonymous, Walnut concealment device with two OTP booklets - THANKS !
    Crypto Museum, August 2015.

  2. H. Keith Melton, Ultimate Spy
    1996. ISBN 0-7513-4791-4.

Further information

OTP booklets hidden inside a real walnut

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Crypto Museum. Created: Monday 07 September 2015. Last changed: Sunday, 15 January 2017 - 09:04 CET.
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