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Proceedings Paper

Design of a tamper resistant public key PC card
Author(s): John C. Droge
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Paper Abstract

The technology available today makes the design ofthe subject card possible and practical. The latter is extremely important for the end item to achieve wide spread use. Only a few years ago, the design was possible, but implementation on a wide scale was not feasible or practical because the manufacturing cost would have made the production ofthe cards too expensive. Today though, by employing the right techniques, one can design a PC Public Key Card that provides confidentiality(encryption); authentication(integrity); and non repudiation in a tamper resistant envelope. Note the term resistant is used as the author believes that the perfect design to achieve a truly tamper proofcard is non existent. One will always be able to reverse engineer the design given time, money and talent. The intent ofthe design discussed in this paper is to make it extremely difficult and therefore very expensive for the person or persons attempting to reverse engineer the PC card. It is essential that the design consider tamper proofing from the very beginnings ofthe project. This means that the indiVidUal chips and/or storage devices that ll comprise the design ofthe Public Key PC card be designed or chosen for their inherent resistance to reverse engineering. This implies that the designer is extremely familiarly with the technology available and it's ability to be manufactured on a wide scale basis. One technology that comes to mind inimediately is vROM for it's inherent resistance to reverse engineering. Remember the assumption that anything can be reverse engineered given the money, time and talent and the goal is to choose a technology that is going to make the person or persons attempting to reverse engineer the design to use and require the most ofeach category. vRom has this potential. It has proven itselfthrough repeated attacks by one of the most sophisticated labs in the country. Another desirable characteristic is the density of the cell family used in the design ofthe Application Specific Integrated Circuits(ASICS) used to formulate the cryptographic engine that is the heart and soul of the Public Key PC card. Fortunately, this characteristic can be measured by examining the cell structures ofthe foundries and going with the foundry that sll meet the objective discussed above. Once the memory elements and ASIC design is stabilized, the next level oftamper design must be addressed. This is the design and layout ofthe PC card itself. Again, the rule ofpicking the most difficult combination oftechniques to frustrate the attacker is paramount. But, one also has to be careful that the design is not so complex that it will be difficult to manufacture on a large scale, otherwise no one will be able to afford to use the PC card and it will become another expensive experiment. Fortunately, todays technology provides a way to achieve an extremely tamper resistant PC card lay out that lends itseifto common wide scale manufacturing techniques. Using techniques such as Tape Automatic Bonding(TAB); Flip Chip mountings; Solder Bumping, etc., etc., in the right combination, followed by encapsulation techniques similar to injection molding, one can provide a product that can not only be manufactured on a wide scale but is also inherently resistant to tampering and resistant to the most sophisticated attempts to reverse engineer the end product. A side benefit ofthis type of design is that it is extremely rugged and hence can be deployed in the most hostile environments. The above is a very briefdiscussion of how one could go about the design of a Tamper Resistant Public Key PC card that provides confidentiality, authentication and integrity ofthe users data. It can and is being done today by a team of highly talented high tech companies, each of which brings their own expertise to focus on a particular aspect of the design as mentioned above, and together produce a card that has no equal in products available now or in the near future. Because this is an on going effort and due to the proprietary information involved in the design, additional details cannot be discussed until the required design protection is in place.

Paper Details

Date Published: 12 March 1996
PDF: 1 pages
Proc. SPIE 2616, Information Protection and Network Security, (12 March 1996); doi: 10.1117/12.234728
Show Author Affiliations
John C. Droge, Mykotronx (United States)

Published in SPIE Proceedings Vol. 2616:
Information Protection and Network Security
Viktor E. Hampel; Clifford B. Neuman; John Perry Barlow, Editor(s)

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