Compact Ring-LWE Cryptoprocessor

Sujoy Sinha Roy, Frederik Vercauteren, Nele Mentens, Donald Donglong Chen, Ingrid Verbauwhede

Research output: Chapter in Book/Report/Conference proceedingChapter

101 Citations (Scopus)


In this paper we propose an efficient and compact processor for a ring-LWE based encryption scheme. We present three optimizations for the Number Theoretic Transform (NTT) used for polynomial multiplication: we avoid pre-processing in the negative wrapped convolution by merging it with the main algorithm, we reduce the fixed computation cost of the twiddle factors and propose an advanced memory access scheme. These optimization techniques reduce both the cycle and memory requirements. Finally, we also propose an optimization of the ring-LWE encryption system that reduces the number of NTT operations from five to four resulting in a 20% speed-up. We use these computational optimizations along with several architectural optimizations to design an instruction-set ring-LWE cryptoprocessor. For dimension 256, our processor performs encryption/decryption operations in 20/9 μs on a Virtex 6 FPGA and only requires 1349 LUTs, 860 FFs, 1 DSP-MULT and 2 BRAMs. Similarly for dimension 512, the processor takes 48/21 μs for performing encryption/decryption operations and only requires 1536 LUTs, 953 FFs, 1 DSP-MULT and 3 BRAMs. Our processors are therefore more than three times smaller than the current state of the art hardware implementations, whilst running somewhat faster.
Original languageEnglish
Title of host publication Cryptographic Hardware and Embedded Systems - CHES 2014
Subtitle of host publication16th International Workshop, Busan, South Korea, September 23-26, 2014. Proceedings
EditorsLejla Batina, Matthew Robshaw
ISBN (Electronic)9783662447093
ISBN (Print)9783662447086
Publication statusPublished - 23 Sept 2014
Event16th International Workshop on Cryptographic Hardware and Embedded Systems (CHES 2014) - Busan , Korea, Democratic People's Republic of
Duration: 23 Sept 201426 Sept 2014

Publication series

NameLecture Notes in Computer Science
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference16th International Workshop on Cryptographic Hardware and Embedded Systems (CHES 2014)
Country/TerritoryKorea, Democratic People's Republic of


  • Lattice-based cryptography
  • ring-LWE
  • Polynomial multiplication
  • Number Theoretic Transform
  • Hardware Implementation


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