Today, we will talk about FPGAs and their role in security and trust. We will start with the basics on FPGA and FPGA-based systems. We will discuss about the advantage of implementing crypto systems using FPGA compared with using ASIC or software. And we'll talk about how FPGA can be used to design hardware security primitives such as physical unclonable function and true random number generator. Next time, we'll talk about the vulnerabilities in both FPGA and FPGA-based system design and their countermeasures. We'll take an approach, which form the supply and the demand model for FPGA design market. In terms of background, if you have some experience in FPGA design, that will be a plus. However, it is not required. But we do need you to know, will be familiar with the physical attacks we have discussed several weeks ago. FPGA stands for field programmable gate arrays. It has input, output blocks on the parameter, and which known as this I/O buffers, and the core programmable fabrics in the middle. This letter L, the large L blocks, this stands for logical blocks and they are the circuitry to implement various Boolean functionalities. The logical blocks, they are connected with wires in the routing channel through the connection blocks, C, and the switch blocks. All these blocks, the L block, C block, and the S block, they are programmable. Today's FPGA devices, they can have billions of transistors under the 10 nanometer technology. Designing this many, logic units with, with such huge capacity, capacity can be a, can be a very, very high challenge. To help FPGA system developers, most of the FPGA vendors, they put many additional features on their FPGA boards in addition to only the, you know, in addition to the programmable logic cells alone. Typically, a FPGA chip has hardwired functional units such as the DSP cores or the embedded processors for certain applications. And also it may have large memory blocks and the high-speed input output and also, as well as other types of design IPs. This is a typical design flow of FPGA-based system. Starting from a given system specification, we first select the FPGA device that will be used to implement the system. Then we use hardware description language, such as, such as Verilog or VHDL to specify the behavior of the system based on the system specification. And the right all type of timing requirements in the design constraint file. So with the help of the FPGA developing tool associate with the FPGA device, we have selected in this face, a bitstream file will be generated as the desired output. These file will be used to configure the FPGA device to provide the system functionality. And pay attention, that's this bit, bitstream file, which normally called configuration bitstream file, will be used for this particular FPGA device. FPGAs from different vendors or different brands, different types, they cannot use the same configuration bitstream files. They have to be reconfigured, in some sense, redesigned. Compare with the ASIC design, or application-specific integrated circuit design, of the system for the same functionality with the same specification, FPGA-based system implementation has a much shorter time to market and an extremely low cost. For example, from this design flow, we don't see any involvement of the silicon foundries. This can save a lot of time and a lot of money. Second, this, the, the same FPGA board can be reprogrammed for different applications, or can be modif, can be re-programmed for modified systems specifics, specifications. These make, make FPGA a very popular design platform. Also compared with the software implementation for the same system specifications, FPGA-based system are in general much faster, more energy and power efficient, and, also have a very, very low power. This is because software implementation normally needs the support from general purpose computers. And, general purpose computers, they're much more expensive than FPGA boards. Now we can see third example of implementi, of implementing a cryptographic system such as a cypher. So one could go with the software implementation, which you can write the C code or Java code, or whichever high level, high level language codes, compile it and then run on a specific system. So this type of implementation has a short implementation time, it is easy to debug and update, and it also has low cost. And, on the other hand, we can go with the hardware implementation, and they will offer the following advantage. So first, you will have extremely low power consumption because we designed the system specific for this cryptosystem. And they will have high throughput, or high performance, and they will have much faster speed than the software implementation. The FPGA-based implementation in some sense is a compromise of hardware and software implementation. So they can enjoy both the advantage from software implementation and from hardware implementation. First, we see the feature of programmable logic cell structures on FPGA boards. These are good for implementation of bit-wise operations. Second, the large build-in memories on FPGA boards. It is in general very good for memory intensive operations, such as the substitution used for many, many deciphers. And third, the reconfigurability of FPGA, we have mentioned earlier, is, is good for reuse and integration. There are many reported cryptosystems developed based on FPGAs. These designs has demonstrated that FPGA have advantages in implementing some popular crypto building blocks, such as the field, finite field arithmetic and the ellip, elliptic curve cryptoprocessors. Here are some specific benefits of implementing crypto on FPGAs. First, FPGA-based implementation offers algorithm flexibility in two, twos, two ways. The agility, we know that many secure particles, such as SSL and IPsec, they are algorithm independent and maybe implemented with multiple or different crypto algorithms and this offers several advantages. So for example if one algorithm is broken, it's compromised. We can simply delete it and use another algorithm or another implementation to avoid the security protocol from, from going dark. And similarly, when there's a new algorithm developed to implement the the secure, security protocol, we can add it into the system for the protocol and, and maybe choose it for best performance. On FPGA systems, this becomes very easy to switch cryptographic algorithms during the operation of the target application, for example, the secure protocols. It also makes the secure protocols more adaptive because up, uploading new standards, or modifying standards for spec, specific applications, are all doable on FPGAs. This may not, or if it is possible, will be very, very expensive to do on application-specific implementations for this ASIC implementations. Second, FPGA implementation offers architecture efficiency. We know that when we fix the values for more variables, the system becomes more like application-specific rather than general purpose. And in general, the system performance with less variables will, will be more performance and hardware efficient. Also, when we need to change the values of these parameters, we can redo the design, and reoptimize it and resynthesize it on a FPGA board but we cannot do these things on ASIC. Third, to have, the same FPGA device can be used for multiple security protocols through run-time reconfigurations, as long as these protocols are not used simultaneously. By doing this way, we do not have to implement separate hardwares for each of the security protocols and we can save a lot of system resource. So next, compared, as we have already seen earlier, compared with software implementation, the FPGA implementation normally will be much faster, often can be ten times or hundreds of times faster. It will have actually a very similar performance as the very powerful general purpose CPUs. However, of course, the dedicated ASIC implementation of secure, security accelerators will be faster than FPGA based system. Finally, and perhaps one of the most important advantage of FPGA implementation is its cost efficiency. By cost, we're talking about both the unit price and also the design time and the design cost. So, FPGAs are ideal for building hardware security primitives. As we have talked about earlier, for both type of PUFs or physical unclonable functions, to delay-based PUF and memory-based PUF, they can be, they can be simply implemented on FPGAs. And to implement a true random number generator, and for a gener, true number, true number, true random number generator to be a good one, we have to evaluate the following criterias. So first, it is the entropy source of the true random number generator. Well, where the randomness comes from? On FPGA and other hardware, due to the fabrication variations and other unpredictable and uncontrollable nuances, there are many sources that can be used to generate randomness such as the phase jitter in the clock network and the path delay. And second, the design footprint. This measures the cost efficiency of the true random number generator. Typical matrix includes area, energy, and the time required to generate one random bit. The low cost and the high availability of FP, of FPGA make it a very good choice based on this criteria. The next that, two matrix, on the testing of random, random bitstreams generated by a true random number generator. These bitstreams, they have to be tested for predictability and other statistical properties. There are many randomness test suites available, such as the diehard and the one maintained by NIST. The random then, the random bitstreams must also be secure against attacks and also robust against the environmental variations. As we have seen in the earlier study of PUF, FPGA and hardware based approaches can meet these requirements. Finally, just like how random was selected as, as a yes, the ease of implementation is also important and, and the FPGA-based true random number generators are easy to implement. Next time we will talk about the vulnerabilities in FPGAs and FPGA-based system design.
