By harnessing fundamental quantum properties, a large-scale quantum computer could undermine currently deployed public-key algorithms. The post-quantum, code-based cryptosystem Classic McEliece (CM) addresses this security concern. However, its large public key size (up to 1.3 MB) poses various hardware implementation challenges. In this article, we focus on the high memory bandwidth requirements of the CM encoding function, in the context of heterogeneous CPU-FPGA devices. More concretely, we target the acceleration of public-key loading and processing from any globally shared or accelerator-private memory system. We present a novel and constant-time accelerator eEnc that exploits the elevated parallelization potential of FPGA devices to yield high-performance results. Our accelerator implements the encoding and the random error vector generation functions, which comprise the main computational load of Encapsulation. Two accelerator design variants are introduced, providing different hardware tradeoffs. Regarding intra-accelerator data communication, and unlike other state-of-the-art (SOTA) works, we combine a streaming protocol with task-level parallelization to remove the need to store the public key in accelerator-private memories. Our proposed design shows new record execution times over its SOTA counterparts, ranging on average from 3.5× up to 7.7× across the five security level parameter sets. Our end-to-end implementation in a Zynq SoC shows an average speedup of 2.2× compared to a 64-bit vectorized CM software-baseline. The elevated logic resource consumption, characteristic of HLS designs, can be readily adjusted with a performance tradeoff.

In 1-out-of-$q$Oblivious Transfer (OT) protocols, a sender Alice is able to send one of$q\ge 2$messages to a receiver Bob, all while being oblivious to which message was transferred. Moreover, the receiver learns only one of these messages. Oblivious Transfer combiners take$n$instances of OT protocols as input, and produce an OT protocol that is secure if sufficiently many of the$n$original OT instances are secure. We present new 1-out-of-$q$OT combiners that are perfectly secure against active adversaries. Our combiners arise from secret sharing techniques. We show that given an$\mathbb {F}_{q}$-linear secret sharing scheme on a set of$n$participants and adversary structure$\mathcal {A}$, we can construct an$n$-server, 1-out-of-$q$OT combiner that is secure against an adversary corrupting either Alice and a set of servers in$\mathcal {A}$, or Bob and a set of servers$B$with$\bar {B}\notin \mathcal {A}$. If the normalized total share size of the scheme is$\ell $, then the resulting OT combiner requires$\ell $calls to OT protocols, and the total amount of bits exchanged during the protocol is$(q^{2}+q+1)\ell \log q$. We also present a construction based on 1-out-of-2 OT combiners that uses the protocol of Crépeau, Brassard and Robert (FOCS 1986). This construction provides smaller communication costs for certain adversary structures, such as threshold ones: For any prime power$q\geq n$, there are$n$-server, 1-out-of-$q$OT combiners that are perfectly secure against active adversaries corrupting either Alice or Bob, and a minority of the OT candidates, exchanging$O(qn\log q)$bits in total.

Many high-demand digital services need to perform several cryptographic operations, such as key exchange or security credentialing, in a concise amount of time. In turn, the security of some of these cryptographic schemes is threatened by advances in quantum computing, as quantum computer could break their security in the near future. Post-quantum cryptography (PQC) is an emerging field that studies cryptographic algorithms that resist such attacks. The National Institute of Standards and Technology (NIST) has selected the CRYSTALS-Kyber Key Encapsulation Mechanism and the CRYSTALS-Dilithium Digital Signature algorithm as primary PQC standards. In this article, we present field-programmable gate array (FPGA)-based hardware accelerators for high-volume operations of both schemes. We apply high-level synthesis (HLS) for hardware optimization, leveraging a batch processing approach to maximize the memory throughput and applying custom HLS logic to specific algorithmic components. Using reconfigurable FPGAs, we show that our hardware accelerators achieve speedups between 3 \(\times\) and 9 \(\times\) over software baseline implementations, even over ones leveraging CPU vector architectures. Furthermore, the methods used in this study can also be extended to the new CRYSTALS-based NIST FIPS drafts, ML-KEM and ML-DSA, with similar acceleration results.

While quantum computers are rapidly becoming more powerful, the current cryptographic infrastructure is imminently threatened. In a preventive manner, the U.S. National Institute of Standards and Technology (NIST) has initiated a process to evaluate quantum-resistant cryptosystems, to form the first post-quantum (PQ) cryptographic standard. Classic McEliece (CM) is one of the most prominent cryptosystems considered for standardization in NIST’s PQ cryptography contest. However, its computational cost poses notable challenges to a big fraction of existing computing devices. This work presents an HLS-based, HW/SW co-design acceleration of the CM Key Encapsulation Mechanism (CM KEM). We demonstrate significant maximum speedups of up to 55.2 ×, 3.3 ×, and 8.7 × in the CM KEM algorithms of key generation, encapsulation, and decapsulation respectively, comparing to a SW-only scalar implementation.