New Class of Multivariate Public Key Cryptosystem, K(XI)RSE(2)PKC, Constructed based on Reed-Solomon Code Along with K(X)RSE(2)PKC over F2\mathbb{F}_2

Extensive studies have been made of the public key cryptosystems based on multivariate polynomials (Multi-variate PKC, MPKC) over $\mathbb{F}_2$ and $\mathbb{F}_2^m$. However most of the proposed MPKC are proved not secure. In this paper, we propose a new class of MPKC based on Reed-Solomon code, referred to as K(XI)RSE(2)PKC. In Appendix, we present another class of MPKC referred to as K(X)RSE(2)PKC over $\mathbb{F}_2$. Both K(X)RSE(2)PKC and K(XI)RSE(2)PKC yield the coding rate of 1.0. We show that the proposed schemes can be sufficiently secure against various attacks, including Gröbner basis attack

Public Key Block Cipher Based on Multivariate Quadratic Quasigroups

We have designed a new class of public key algorithms based on quasigroup string transformations using a specific class of quasigroups called \emph{multivariate quadratic quasigroups (MQQ)}. Our public key algorithm is a bijective mapping, it does not perform message expansions and can be used both for encryption and signatures. The public key consist of $n$ quadratic polynomials with $n$ variables where $n=140, 160, \ldots$. A particular characteristic of our public key algorithm is that it is very fast and highly parallelizable. More concretely, it has the speed of a typical modern symmetric block cipher -- the reason for the phrase \emph{ A Public Key Block Cipher } in the title of this paper. Namely the reference C code for the 160--bit variant of the algorithm performs decryption in less than 11,000 cycles (on Intel Core 2 Duo -- using only one processor core), and around 6,000 cycles using two CPU cores and OpenMP 2.0 library. However, implemented in Xilinx Virtex-5 FPGA that is running on 249.4 MHz it achieves decryption throughput of 399 Mbps, and implemented on four Xilinx Virtex-5 chips that are running on 276.7 MHz it achieves encryption throughput of 44.27 Gbps. Compared to fastest RSA implementations on similar FPGA platforms, MQQ algorithm is more than 10,000 times faster

Efficient Cryptanalysis of RSE(2)PKC and RSSE(2)PKC

In this paper, we study the new class step-wise Triangular Schemes (STS) of public key cryptosystems (PKC) based on multivariate quadratic polynomials. In these schemes, we have m the number of equations, n the number of variables, L the number of steps/layers, r the number of equations/variables per step, and q the size of the underlying field. We present two attacks on the STS class by exploiting the chain of the kernels of the private key polynomials. The first attack is an inversion attack which computes the message/signature for given ciphertext/message in O(mn³Lq^r + n²Lrq^r), the second is a structural attack which recovers an equivalent version of the secret key in O(mn³Lq^r + mn^4) operations. Since the legitimate user has workload q^r for decrypting/computing a signature, the attacks presented in this paper are very efficient. As an application, we show that two special instances of STS, namely RSE(2)PKC and RSSE(2)PKC, recently proposed by Kasahara and Sakai, are insecure