Miniflex UA-8036

Portable cipher unit for civil applications Miniflex was a high-grade cipher machine developed by Philips Usfa between 1976 and 1982 in co-operation with the German manufacturer AEG Telefunken. It was a small portable cryptographic machine that was in fact a cut-down version of the NATO-issue Picoflex, produced by the same manufacturers. In all, over 300 Miniflex and Picoflex units were produced.

Miniflex could be used completely stand-alone and was powered by 5 penlight batteries (AA-size). The user could type a message on the keyboard and read the encrypted text from the display. He could then write down the cipher text and transmit it via letter, telex, telegram, morse code or by any other means. Miniflex had the same expansion capabilities as Picoflex, but in practice the most common accessories were the printer and the acoustic telephone coupler. The radio modem was optional. The image on the right shows the bare Miniflex unit, whithout any of its accessories.

Although Miniflex was also available as a green military variant, it was mainly intended for civil applications. It is therefore much less sophisticated than the NATO-approved Picoflex. The cryptogrphic algorithm of the Miniflex is entirely implemented in software.

Using Miniflex

Miniflex was often seated in an executive style briefcase, that was commonly used by business men in those days, and could therefore be carried inconspiciously. It was intended for civil applications, such as diplomatic services, international banks, oil companies, etc.

The image on the right shows a typical Miniflex configuration built into a thin Samsonite case. The printer is bolted to the left side of the main unit. The acoustical telephone coupler is fitted behind the main unit and connects to it via a plug at the right. Two black bags with zippers are fitted at either side of the telephone coupler. They contain spare rolls for the printer and a mains adapter that can be used instead of the batteries. The adapter was manufactured by Telefunken.

Miniflex could hold only one crypto key at a time. Each key was exactly 24 characters long (A-Z and 1-6) and consisted of 20 characters for the key itself, one fill-in character and three for the indicator. The user would take the key from a so-called key list. Once the key was entered, Miniflex would respond with a 5-character code that should match the checksum in the key list. After that, the operator could encrypt or decrypt a message off-line.

Both the cipher text and the plain text could be printed on the (optional) thermal printer that was attached to the left of the main unit. The text is printed in 5-letter groups and two of such groups fit on each line. This image shows the printer with its lid opened. Inside the printer is the narrow silver paper roll. The transparent lid has an embedded metal grid that gives some degree of TEMPEST shielding. The printer has its own battery pack and power switch.