The dancing, cryptic mind of Carol Marsh

Wednesday 27th August 2008
Carol Marsh in work mode

If you visit the website of Carol Marsh, it’s easy to see what her current focus in on: investigating cryptographic technologies for enforcing IP licenses in IP cores and investigating technologies for detecting products which incorporate unlicensed IP cores. Her newest page is on cryptography book reviews, providing two 'must reads' for budding cryptographers and four 'next reads' as well.

Back in 2005, the iSLI advertised an Engineering Doctorate position working with the FPGA Super Computer Group at Edinburgh University. Marsh applied for this and was accepted by Dr Tom Kean of Algotronix.  Dr Kean designed the CAL device that was implemented into the Xilinx FPGA and Marsh wrote about this in her first MSc dissertation.

She is now in her final year of the EngD, enjoying it immensely, and considers it a great privilege to be working with Dr Kean. Marsh says that the advances in IP protection approach are due to him. "He is brilliant on the subject.  It was his idea to use the undesirable 'side channels' in which a considerable amount of research had already been devoted to hiding them." 

“Side channels show power spikes, electromagnetic activity and temperature differences. It was decided that the side channel temperature would be a good way to go."  So the cryptography we have developed deliberately uses ‘side channels’.”

The DesignTag is an active circuit present in a finished chip, not merely an optical identification code on special mask layers, or a watermark in the design source code. The Tag system is made up of a small ‘tag’ circuit built into the IP core or chip which needs protection; a sensor for collecting activity data from the tagged chip, software which processes that collected data; and a web-based database of tag codes and design information.

For the owners of the IP Core or a complete chip design, it has been difficult and expensive to prove their IP is being used illegally in a product. In the case of silicon chips, the only practical method of detecting an IP Core, has been to obtain a sample of the product under suspicion, send it to a specialist laboratory for analysis and a 'tear down' or reverse engineering.  But detecting the presence of an IP Core in designs implemented on 'anti-fuse' FPGAs or designs for a SRAM FPGA, in which the bitstream is already protected by cryptography, is virtually impossible.

Now the small security DesignTag circuit is added to IP cores (or to complete designs). A reader ‘wand’ detects and receives information from the ‘security tag’ to provide a method of proving illegal use of an IP core. This is both non-invasive, quick and does not affect the system functionality.  The technique can detect the IP Tag even if it is implemented on an FPGA where the bitstream is encrypted.  And as well as protecting against design piracy, the tag combats the increasing problem of low-cost ‘equivalent' chips,  falsely marked as coming from reputable manufacturers.

"Most customers are good about IP," says Marsh, "and quite often breaches of IP are not deliberate. DesignTag is also helpful for design houses to pick up on accidental breaches of IP use. We've got one version of the new Tag out now for over a month, "says Marsh "and we've demonstrated it at several conferences to many people."

"Basically the 'active tag' generates heat in a circuit and an outside monitor detects the tag. We are also working on a passive tag, a heat circuit outside the chip and providing detection within the basic design. It's not at production level, but currently a prototype."

Asked how she personally found maths teaching at school, Marsh says she was lucky in having an excellent teacher.

"I was terrible at exams when I was younger. In third year, my maths teacher wanted us to sit our O grade, but we weren’t allowed to so we started the Higher syllabus in fourth year and went back and sat the O grade at the end of fourth year. I only got a B in the O grade, but the teacher knew that I had no problems with Higher Maths. By the time I left school I had a good grounding in maths and loved it so much I went on to do physics and again I had an excellent teacher.

"When my oldest son went to school, his teacher was my physics teacher and he remembered me. I had thought of becoming a teacher, but I was in a statistics class and had watched a teacher who simply couldn't control the classes, and thought 'that would be me.'

It turned her to computing engineering, programming and learning to fix things.  "I was really lucky," she reflects. "Computing as a subject was quite new 25 years ago" She has now done her own web site with text editor, and gone back to school to learn HTML language.

"I started working with FPGAs in the early 1990s when FPGA replaced PLDs in systems, but while the actual devices keep changing so do the applications and the tools for these have not kept up with them.  IP security is one of the critical elements for FPGA progress."

How did she get into dancing?  "I did aerobics for 12 years, and never though about teaching. But I did take the exam, and when one of the teachers left, I was given the classes. That's really how I became a fitness instructor and it was great for building self confidence. Later on I qualified as a Dance instructor."

"I'm running two classes just now, but do not have time for more," she says, though she admits to thinking about taking up lecturing, finding an appeal in an advisory role and enjoying being with and helping people. "I don't want to be just an engineer sitting at a desk and working on problems."

Judging by her record, small chance of that.


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