A Lightweight and Efficient Encryption/Decryption Coprocessor for RLWE-Based Cryptography

Lattice-based cryptography has experienced significant advancements in recent years due to its versatility and simplicity. The ring learning with errors (RLWE) problem is widely adopted in lattice-based cryptography. However, the polynomial multiplication is the performance bottleneck of RLWE-based cryptography, which requires further examination. In this brief, a lightweight and efficient encryption/decryption coprocessor for RLWE-based cryptography is proposed. The time complexity of the Schoolbook polynomial multiplication (SPM) is reduced from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${n}^{2}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {n}^{ {2}} {/8}$ </tex-math></inline-formula> by enhancing multiplication parallelism. Moreover, an optimized structure for the Compressed cumulative distribution table (CDT) Gaussian sampler is proposed, resulting in 22.2% reduction in storage resource. The proposed SPM structure demonstrates a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.3\times $ </tex-math></inline-formula> performance speedup and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.7\times $ </tex-math></inline-formula> hardware efficiency for the encryption core, compared with state-of-the-art SPM accelerators. Additionally, it achieves a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4\times $ </tex-math></inline-formula> performance speedup and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.2\times $ </tex-math></inline-formula> improvements on hardware efficiency for the decryption core.