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See detailHigh-Performance Ideal Lattice-Based Cryptography on 8-Bit AVR Microcontrollers
Liu, Zhe; Pöppelmann, Thomas; Oder, Tobias et al

in ACM Transactions on Embedded Computing Systems (2017), 16(4), 117

Over recent years lattice-based cryptography has received much attention due to versatile average-case problems like Ring-LWE or Ring-SIS that appear to be intractable by quantum computers. In this work ... [more ▼]

Over recent years lattice-based cryptography has received much attention due to versatile average-case problems like Ring-LWE or Ring-SIS that appear to be intractable by quantum computers. In this work, we evaluate and compare implementations of Ring-LWE encryption and the bimodal lattice signature scheme (BLISS) on an 8-bit Atmel ATxmega128 microcontroller. Our implementation of Ring-LWE encryption provides comprehensive protection against timing side-channels and takes 24.9ms for encryption and 6.7ms for decryption. To compute a BLISS signature, our software takes 317ms and 86ms for verification. These results underline the feasibility of lattice-based cryptography on constrained devices. [less ▲]

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See detailElliptic Curve Cryptography with Efficiently Computable Endomorphisms and Its Hardware Implementations for the Internet of Things
Liu, Zhe UL; Groszschädl, Johann UL; Hu, Zhi et al

in IEEE Transactions on Computers (2017), 66(5), 773-785

Verification of an ECDSA signature requires a double scalar multiplication on an elliptic curve. In this work, we study the computation of this operation on a twisted Edwards curve with an efficiently ... [more ▼]

Verification of an ECDSA signature requires a double scalar multiplication on an elliptic curve. In this work, we study the computation of this operation on a twisted Edwards curve with an efficiently computable endomorphism, which allows reducing the number of point doublings by approximately 50 percent compared to a conventional implementation. In particular, we focus on a curve defined over the 207-bit prime field Fp with p = 2^207 - 5131. We develop several optimizations to the operation and we describe two hardware architectures for computing the operation. The first architecture is a small processor implemented in 0.13 μm CMOS ASIC and is useful in resource-constrained devices for the Internet of Things (IoT) applications. The second architecture is designed for fast signature verifications by using FPGA acceleration and can be used in the server-side of these applications. Our designs offer various trade-offs and optimizations between performance and resource requirements and they are valuable for IoT applications. [less ▲]

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See detailPrivate Mobile Pay-TV From Priced Oblivious Transfer
Biesmans, Wouter; Balasch, Josep; Rial Duran, Alfredo UL et al

in IEEE Transactions on Information Forensics & Security (2017)

In pay-TV, a service provider offers TV programs and channels to users. To ensure that only authorized users gain access, conditional access systems (CAS) have been proposed. In existing CAS, users ... [more ▼]

In pay-TV, a service provider offers TV programs and channels to users. To ensure that only authorized users gain access, conditional access systems (CAS) have been proposed. In existing CAS, users disclose to the service provider the TV programs and channels they purchase. We propose a pay-per-view and a pay-per-channel CAS that protect users' privacy. Our pay-per-view CAS employs priced oblivious transfer (POT) to allow a user to purchase TV programs without disclosing which programs were bought to the service provider. In our pay-per-channel CAS, POT is employed together with broadcast attribute-based encryption (BABE) to achieve low storage overhead, collusion resistance, efficient revocation and broadcast efficiency. We propose a new POT scheme and show its feasibility by implementing and testing our CAS on a representative mobile platform. [less ▲]

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See detailEfficient Ring-LWE Encryption on 8-bit AVR Processors
Liu, Zhe UL; Seo, Hwajeong; Roy, Sujoy Sinha et al

in Güneysu, Tim; Handschuh, Helena (Eds.) Cryptographic Hardware and Embedded Systems - CHES 2015, 17th International Workshop, Saint-Malo, France, September 13-16, 2015, Proceedings (2015, September)

Public-key cryptography based on the "ring-variant" of the Learning with Errors (ring-LWE) problem is both efficient and believed to remain secure in a post-quantum world. In this paper, we introduce a ... [more ▼]

Public-key cryptography based on the "ring-variant" of the Learning with Errors (ring-LWE) problem is both efficient and believed to remain secure in a post-quantum world. In this paper, we introduce a carefully-optimized implementation of a ring-LWE encryption scheme for 8-bit AVR processors like the ATxmega128. Our research contributions include several optimizations for the Number Theoretic Transform (NTT) used for polynomial multiplication. More concretely, we describe the Move-and-Add (MA) and the Shift-Add-Multiply-Subtract-Subtract (SAMS2) technique to speed up the performance-critical multiplication and modular reduction of coefficients, respectively. We take advantage of incompletely-reduced intermediate results to minimize the total number of reduction operations and use a special coefficient-storage method to decrease the RAM footprint of NTT multiplications. In addition, we propose a byte-wise scanning strategy to improve the performance of a discrete Gaussian sampler based on the Knuth-Yao random walk algorithm. For medium-term security, our ring-LWE implementation needs 590k, 672k, and 276k clock cycles for key-generation, encryption, and decryption, respectively. On the other hand, for long-term security, the execution time of key-generation, encryption, and decryption amount to 2.2M, 2.6M, and 686k cycles, respectively. These results set new speed records for ring-LWE encryption on an 8-bit processor and outperform related RSA and ECC implementations by an order of magnitude. [less ▲]

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