LFSR-based bit-serial GF(^2m) multipliers using irreducible trinomials

In this article, a new architecture of bit-serial polynomial basis (PB) multipliers over the binary extension field GF(^2m) generated by irreducible trinomials is presented. Bit-serial GF(^2m) PB multiplication offers a performance/area trade-off that is very useful in resource constrained applications. The architecture here proposed is based on LFSR (Linear-Feedback Shift Register) and can perform a multiplication in m clock cycles with a constant propagation delay of T_A + T_X. These values match the best time results found in the literature for bit-serial PB multipliers with a slight reduction of the space complexity. Furthermore, the proposed architecture can perform the multiplication of two operands for t different finite fields GF(^2m) generated by t irreducible trinomials simultaneously in m clock cycles with the inclusion of t(m - 1) flipflops and tm XOR gates

Improved throughput bit-serial multiplier for GF(2m) fields

High throughput is a crucial factor in bit-serial GF(2m) fields multiplication for a variety of different applications including cryptography, error coding detection and computer algebra. The throughput of a multiplier is dependent on the required number of clock cycles to reach a result and its critical path delay. However, most bit-serial GF(2m) multipliers do not manage to reduce the required number of clock cycles below the threshold of m clock cycles without increasing dramatically their critical path delay. This increase is more evident if a multiplier is designed to be versatile. In this article, a new versatile bit-serial MSB multiplier for GF(2m) fields is proposed that achieves a 50% increase on average in throughput when compared to other designs, with a very small increase in its critical path delay. This is achieved by an average 33.4% reduction in the required number of clock cycles below m. The proposed design can handle arbitrary bit-lengths upper bounded by m and is suitable for applications where the field order may vary

Hardware Implementations for Symmetric Key Cryptosystems

The utilization of global communications network for supporting new electronic applications is growing. Many applications provided over the global communications network involve exchange of security-sensitive information between different entities. Often, communicating entities are located at different locations around the globe. This demands deployment of certain mechanisms for providing secure communications channels between these entities. For this purpose, cryptographic algorithms are used by many of today\u27s electronic applications to maintain security. Cryptographic algorithms provide set of primitives for achieving different security goals such as: confidentiality, data integrity, authenticity, and non-repudiation. In general, two main categories of cryptographic algorithms can be used to accomplish any of these security goals, namely, asymmetric key algorithms and symmetric key algorithms. The security of asymmetric key algorithms is based on the hardness of the underlying computational problems, which usually require large overhead of space and time complexities. On the other hand, the security of symmetric key algorithms is based on non-linear transformations and permutations, which provide efficient implementations compared to the asymmetric key ones. Therefore, it is common to use asymmetric key algorithms for key exchange, while symmetric key counterparts are deployed in securing the communications sessions. This thesis focuses on finding efficient hardware implementations for symmetric key cryptosystems targeting mobile communications and resource constrained applications. First, efficient lightweight hardware implementations of two members of the Welch-Gong (WG) family of stream ciphers, the WG$\left(29,11\right)$ and WG-$16$, are considered for the mobile communications domain. Optimizations in the WG$\left(29,11\right)$ stream cipher are considered when the $GF\left(2^{29}\right)$ elements are represented in either the Optimal normal basis type-II (ONB-II) or the Polynomial basis (PB). For WG-$16$, optimizations are considered only for PB representations of the $GF\left(2^{16}\right)$ elements. In this regard, optimizations for both ciphers are accomplished mainly at the arithmetic level through reducing the number of field multipliers, based on novel trace properties. In addition, other optimization techniques such as serialization and pipelining, are also considered. After this, the thesis explores efficient hardware implementations for digit-level multiplication over binary extension fields $GF\left(2^{m}\right)$. Efficient digit-level $GF\left(2^{m}\right)$ multiplications are advantageous for ultra-lightweight implementations, not only in symmetric key algorithms, but also in asymmetric key algorithms. The thesis introduces new architectures for digit-level $GF\left(2^{m}\right)$ multipliers considering the Gaussian normal basis (GNB) and PB representations of the field elements. The new digit-level $GF\left(2^{m}\right)$ single multipliers do not require loading of the two input field elements in advance to computations. This feature results in high throughput fast multiplication in resource constrained applications with limited capacity of input data-paths. The new digit-level $GF\left(2^{m}\right)$ single multipliers are considered for both the GNB and PB. In addition, for the GNB representation, new architectures for digit-level $GF\left(2^{m}\right)$ hybrid-double and hybrid-triple multipliers are introduced. The new digit-level $GF\left(2^{m}\right)$ hybrid-double and hybrid-triple GNB multipliers, respectively, accomplish the multiplication of three and four field elements using the latency required for multiplying two field elements. Furthermore, a new hardware architecture for the eight-ary exponentiation scheme is proposed by utilizing the new digit-level $GF\left(2^{m}\right)$ hybrid-triple GNB multipliers