30 research outputs found
SIKE Round 2 Speed Record on ARM Cortex-M4
We present the first practical software implementation of Supersingular
Isogeny Key Encapsulation (SIKE) round 2, targeting NIST’s 1, 2, and 5 security
levels on 32-bit ARM Cortex-M4 microcontrollers. The proposed library introduces a
new speed record of SIKE protocol on the target platform. We achieved this record
by adopting several state-of-the-art engineering techniques as well as highly-optimized
hand-crafted assembly implementation of finite field arithmetic. In particular, we
carefully redesign the previous optimized implementations of filed arithmetic on 32-bit
ARM Cortex-M4 platform and propose a set of novel techniques which are explicitly
suitable for SIKE/SIDH primes. Moreover, the proposed arithmetic implementations
are fully scalable to larger bit-length integers and can be adopted over different
security levels. The benchmark result on STM32F4 Discovery board equipped with
32-bit ARM Cortex-M4 microcontrollers shows that the entire key encapsulation
over p434 takes about 326 million clock cycles (i.e. 1.94 seconds @168MHz). In
contrast to the previous optimized implementation of the isogeny-based key exchange
on low-power 32-bit ARM Cortex-M4, our performance evaluation shows feasibility
of using SIKE mechanism on the target platform. In comparison to the most of the
post-quantum candidates, SIKE requires an excessive number of arithmetic operations,
resulting in significantly slower timings. However, its small key size makes this scheme
as a promising candidate on low-end microcontrollers in the quantum era by ensuring
the lower energy consumption for key transmission than other schemes
Ambient Temperature Influences Australian Native Stingless Bee (Trigona carbonaria) Preference for Warm Nectar
The interaction between flowers and insect pollinators is an important aspect of the reproductive mechanisms of many plant species. Several laboratory and field studies indicate that raising flower temperature above ambient can be an advantage in attracting pollinators. Here we demonstrate that this preference for warmer flowers is, in fact, context-dependent. Using an Australian native bee as a model, we demonstrate for the first time a significant shift in behaviour when the ambient temperature reaches 34°C, at which point bees prefer ambient temperature nectar over warmer nectar. We then use thermal imaging techniques to show warmer nectar maintains the flight temperature of bees during the period of rest on flowers at lower ambient temperatures but the behavioural switch is associated with the body temperature rising above that maintained during flight. These findings suggest that flower-pollinator interactions are dependent upon ambient temperature and may therefore alter in different thermal environments
Nanoscale Metallic Iron for Environmental Remediation: Prospects and Limitations
The amendment of the subsurface with nanoscale metallic iron particles
(nano-Fe0) has been discussed in the literature as an efficient in situ
technology for groundwater remediation. However, the introduction of this
technology was controversial and its efficiency has never been univocally
established. This unsatisfying situation has motivated this communication whose
objective was a comprehensive discussion of the intrinsic reactivity of
nano-Fe0 based on the contemporary knowledge on the mechanism of contaminant
removal by Fe0 and a mathematical model. It is showed that due to limitations
of the mass transfer of nano-Fe0 to contaminants, available concepts cannot
explain the success of nano-Fe0 injection for in situ groundwater remediation.
It is recommended to test the possibility of introducing nano-Fe0 to initiate
the formation of roll-fronts which propagation would induce the reductive
transformation of both dissolved and adsorbed contaminants. Within a
roll-front, FeII from nano-Fe0 is the reducing agent for contaminants. FeII is
recycled by biotic or abiotic FeIII reduction. While the roll-front concept
could explain the success of already implemented reaction zones, more research
is needed for a science-based recommendation of nano- Fe0 for subsurface
treatment by roll-front
Reverse Product-Scanning Multiplication and Squaring on 8-bit AVR Processors
High performance, small code size, and good scalability are important requirements for software implementations of multi-precision arithmetic algorithms to fit resource-limited embedded systems. In this paper, we describe optimization techniques to speed up multi-precision multiplication and squaring on the AVR ATmega series of 8-bit microcontrollers. First, we present a new approach to perform multi-precision multiplication, called Reverse Product Scanning (RPS), that resembles the hybrid technique of Gura et al., but calculates the byte-products in the inner loop in reverse order. The RPS method processes four bytes of the two operands in each iteration of the inner loop and employs two carry-catcher registers to minimize the number of add instructions. We also describe an optimized algorithm for multi-precision squaring based on the RPS technique that is, depending on the operand length, up to 44.3% faster than multiplication. Our AVR Assembly implementations of RPS multiplication and RPS squaring occupy less than 1 kB of code space each and are written in a parameterized fashion so that they can support operands of varying length without recompilation. Despite this high level of flexibility, our RPS multiplication outperforms the looped variant of Hutter et al.'s operand-caching technique and saves between 40 and 51% of code size. We also combine our RPS multiplication and squaring routines with Karatsuba's method to further reduce execution time. When executed on an ATmega128 processor, the "karatsubarized RPS method" needs only 85k clock cycles for a 1024-bit multiplication (or 48k cycles for a squaring). These results show that it is possible to achieve high performance without sacrificing code size or scalability
The interaction of temperature and sucrose concentration on foraging preferences in bumblebees
Several authors have found that flowers that are warmer than their surrounding environment have an advantage in attracting pollinators. Bumblebees will forage preferentially on warmer flowers, even if equal nutritional reward is available in cooler flowers. This raises the question of whether warmth and sucrose concentration are processed independently by bees, or whether sweetness detectors respond to higher sugar concentration as well as higher temperature. We find that bumblebees can use lower temperature as a cue to higher sucrose reward, showing that bees appear to process the two parameters strictly independently. Moreover, we demonstrate that sucrose concentration takes precedence over warmth, so that when there is a difference in sucrose concentration, bees will typically choose the sweeter feeder, even if the less sweet feeder is several degrees warmer
Mutations perturbing petal cell shape and anthocyanin synthesis influence bumblebee perception of Antirrhinum majus flower colour
We wished to understand the effects on pollinator behaviour of single mutations in plant genes controlling flower appearance. To this end, we analysed snapdragon flowers (Antirrhinum majus), including the mixta and nivea mutants, in controlled laboratory conditions using psychophysical tests with bumblebees