101,201 research outputs found
Efficient Aldol-Type Reaction ofO-Protected α-Hydroxy Aldehydes andN-Trimethylsilyl Ketene Imines: Synthesis of β,γ-Dihydroxy-Nitriles
No full textAn uncatalyzed aldol-type reaction of aromatic N-trimethylsilyl ketene imines with O-protected -trialkylsilyloxy or -benzyloxy aldehydes is reported. It is shown that N-trimethylsilyl ketene imines (SKIs) are essential for the success of this aldol-type reaction, and that almost complete control of stereochemistry in the formation of the stereocentre vicinal to the stereogenic centre present in the starting aldehyde is seen when these compounds are used. A very high syn stereoselectivity was observed at room temperature, and a reversal of stereoselectivity to favour the formation of the anti product may be achieved at low temperature. Preliminary theoretical calculations support the hypothesis that the aldol-type reaction is facilitated by the formation of a cyclic transition state, with concomitant silatropic migration from the ketene imine-nitrogen to the aldehyde oxygen. The catalyst-free aldol reaction has been applied to aromatic N-trimethylsilyl ketene imines bearing two different aromatic groups. In these reactions, the diastereoselectivity for the stereocentre arising from aldehyde sp(2) carbon remained extremely high, but the stereoselectivity for the formation of the new quaternary stereocentre was unsatisfactory
Turbo-coded CDMA-based two-way relaying
No full textIn this contribution, we have studied the performance of a Turbo-Coded (TC) Code Division Multiple Access (CDMA) based two-way relaying scheme. More explicitly, we employ a seven-user CDMA model, where two of the CDMA users are communicating with each other with the aid of an additional relay node, while the other five CDMA users are interferers. More explicitly, two CDMA users exchange their information frames within two timeslots. Note that the conventional one-way relaying system can only transmit one information frame within two timeslots because the relay node is half-duplex, where it cannot listen and transmit simultaneously. We found that our proposed TC-CDMA two-way relaying scheme is capable of attaining over 4 dB of SNR gain at a Bit Error Rate (BER) of 10-6 when compared to a conventional non-cooperative TC-CDMA system. We also found that there is about two dB of SNR loss at a BER of 10-6, due to the error propagation from the relay node. The proposed scheme exploits the benefits of TC and CDMA schemes in order to assist the two-way relaying system to operate with a reduced transmit power. The reduction of the transmit power can also be exploited for increasing the coverage area of a cellular cell. Hence, the TC-CDMA two-way relaying scheme is a good candidate for future generation mobile system
Does Broader-Based Local Government affect Expenditure on Public Long-Term Care Insurance? The Case of Japan
No full textThis paper considers the possible effects of broader-based local government, especially extended associations, in Japanese local public finance. We mainly analyze scale effects in public long-term care insurance expenditure, with our results indicating a U shaped expenditure structure. We also show that expenditures associated with extended associations decrease more rapidly than ordinary municipal expenditures. These findings suggest that expenditure of appropriate population size extended associations larger than single municipality.local public finance, scale effects, broader-based local government, extended association, long-term care insurance
Piecing Together Sha Po
No full textHong Kong boasts a number of rich archaeological sites behind sandy bays. Among these backbeaches is Sha Po on Lamma Island, a site which has long captured the attention of archaeologists. However, until now no comprehensive study of the area has ever been published.
Piecing Together Sha Po presents the first sustained analysis, framed in terms of a multi-period social landscape, of the varieties of human activity in Sha Po spanning more than 6,000 years. Synthesising decades of earlier fieldwork together with Atha and Yip’s own extensive excavations conducted in 2008-2010, the discoveries collectively enabled the authors to reconstruct the society in Sha Po in different historical periods.
The artefacts unearthed from the site—some of them unique to the region—reveal a vibrant past which saw the inhabitants of Sha Po interacting with the environment in diverse ways. Evidence showing the mastery of quartz ornament manufacture and metallurgy in the Bronze Age suggests increasing craft specialisation and the rise of a more complex, competitive society. Later on, during the Six Dynasties-Tang period, Sha Po turned into a centre in the region’s imperially controlled kiln-based salt industry. Closer to our time, in the nineteenth century the farming and fishing communities in Sha Po became important suppliers of food and fuel to urban Hong Kong. Ultimately, this ground-breaking work tells a compelling story about human beings’ ceaseless reinvention of their lives through the lens of one special archaeological site.</p
Xenoastrosphaeriella aquatica sp. nov. from freshwater habitat in Yunnan Province, China
No full textLuo, Zong-Long, Bao, Dan-Feng, Li, Long-Li, Luan, Sha, Su, Hong-Yan (2022): Xenoastrosphaeriella aquatica sp. nov. from freshwater habitat in Yunnan Province, China. Phytotaxa 544 (2): 193-200, DOI: 10.11646/phytotaxa.544.2.
Litarcturus kexueiae Liu & Sha, 2015, sp. nov.
No full text<i>Litarcturus kexueiae</i> sp. nov. <p>Figs 1–5</p> <p> <b>Material examined.</b> Holotype, adult male (total length, 13.8 mm, without antennae), MBM 240861, Okinawa Trough (27°40.300´N; 126°54.174´E), RY0231, depth 2115 m, bottom sandy mud, coll. Zhongli Sha, by Agassiz trawl, 23 April 2014.</p> <p> <b>Description.</b> Body (Fig. 1 A–B) length 13.8 mm. Eyes rounded, large and protruding, 0.36 of lateral length of cephalothorax. Body long, slender, pereonite 1 fused with head; dorsal transverse ridge between cephalothorax and pereonite 1. Preocular spines absent; supraocular spines long, slender and directed anteriorly, unarmed, not covering the eyes in dorsal view, about 3.0 times as long as diameter of eye. Further dorsal spines are lacking. All pereonites unarmed, with rough cuticle. Pereonites 1–3 of about same length and width; pereonite 4 longest, slightly narrower than pereonites 1–3, of about the same width as pereonites 6–7; pereonite 5 slightly longer than pereonites 4 and 6–7. Tergites of pereonites 5–7 with concave posterior border into which the following segment fits when the animal bends dorsally.</p> <p>All pleonites fused with pleotelson, unarmed. Pleotelson length about 0.25 times body length, width about 0.5 of total pleotelson length, partly with small scattered tubercles. Posterolateral pleotelsonic spines strong and straight, unarmed, at 0.62 of pleotelson length, about 0.6 times as long as caudal part of pleotelson. Pleotelson apex prominent, triangular and caudally rounded.</p> <p>Antennula (Fig. 3 A): length 0.18 times body length, with 2 flagellar articles; peduncular article 1 broadest, 1.4 times longer than wide and shorter than second one, unarmed; article 2 longest, 1.2 times as long as article 1, unarmed; article 3 slightly shorter than article 2, unarmed; flagellar article 1 a very short ring with 1 lateral slender bristle; article 2 2.6 times as long as peduncular article 3, with 8 groups of 2 aesthetascs accompanied by several simple setae, apically 2 terminal simple setae and another 2 aesthetascs.</p> <p>Antenna (Fig. 3 B): peduncle length 0.9 times body length; article 2 short, 0.3 length of article 3, with 2 parallel rows of short setae; articles 3 and 4 with 2 parallel rows of setae, arranged in groups of 1 long and 1 shorter setae; article 5 long and slender, with a row of short setae, arranged in groups of 1 long and 1 shorter setae; flagellum broken, article 1 with 2 parallel rows of short setae.</p> <p>Mouthparts typical of the family (Fig. 2 A–C).</p> <p>Maxilliped (Fig. 2 D) with a long oval-shaped epipod, strong endite and five-segmented palp. Epipodite covered with fine setae laterally and medially. Endite as long as epipodite, surpassing the middle of the second palp article, distal margin covered with fine setae and 7 robust setulate setae, distolaterally with 3 short plumose setae.</p> <p>Palp article 1 shortest, length 0.7 times length of second article, with few short simple setae on ventral margin and ventrolateral surface; palpal article 2 with short simple setae on ventral margin and ventrolateral surface; article 3 longest, 1.9 times longer than article 2, with dense simple and pectinate setae on ventral margin and ventrolateral surface and 2 long pectinate setae dorsodistally; article 4 about 1.5 times as long as article 2, with dense simple and pectinate setae on ventral margin and ventrolateral surface and 4 long pectinate setae dorsodistally; article 5 1.4 times longer than article 1, with long simple and pectinate setae apically.</p> <p>Pereopod 1 (Fig. 3 C) more robust than pereopods 2–7; basis longer than propodus, 2.1 times longer than wide, distoventrally with several long and slender simple setae, dorsal surface equipped with row of setules; ischium 0.9 times basis length, 1.7 times longer than wide, ventrally with dense long simple setae on distal half; merus 0.5 times ischium length, 1.8 times wider than long, with dense long simple setae ventrally and 2 anterodistal setae, carpus trapezoidal, 1.6 times wider than long, about as long as merus, with dense long simple setae ventrally; propodus subchelate and slender, 2.2 times carpus length, twice as long as wide; ventrally and partly laterally with dense long slender simple setae, dorsolateral surface with dense pectinate setae; dactylus shorter than propodus, 3.3 times longer than wide, with a unguis and a secondary unguis, and between bearing a seta, with several long and slender simple setae.</p> <p>Pereopods 2–4 similar, with long setae on posteromedial margins, without spines on anterolateral margins; long filter setae present on ischium, merus, carpus and propodus but lacking on dactylus (unknown in pereopod 3). Pereopod 2 (Fig. 3 D) basis 1.8 times longer than wide, dorsally unarmed, distoventrally with several long and slender simple setae; ischium length 0.7 times basis length, 1.4 times longer than wide, dorsally unarmed, ventrally with 2 parallel rows of setae, every row with 6 groups of setae and arranged in groups of 1 long filtering seta and 1 shorter simple seta; merus 1.5 times ischium length, 1.8 times longer than wide, with 1 small simple seta distodorsally, ventrally with 2 parallel rows of setae, every row with 6 groups of setae and arranged in groups of 1 long filtering seta and 1 shorter simple seta; carpus 2.2 times merus length, 6.8 times longer than wide, with several small simple setae dorsally, ventrally with 2 parallel rows of setae, every row with 16 groups of setae and arranged in groups of 1 long filtering seta and 1 shorter simple seta; propodus almost as long as carpus, 9.8 times longer than wide, with 2 moderate setae and 3 small simple setae dorsally, ventrally with 2 parallel rows of setae, every row with 14 groups of setae and arranged in groups of 1 long filtering seta and 1 shorter simple seta; dactylus 0.5 times propodus length, 11.1 times longer than wide, with 4 small simple setae dorsally, 2 small simple setae ventrally; unguis 0.5 times dactylus length, with a short ventral claw and a medial seta.</p> <p>Pereopod 3 (Fig. 4 A) basis 2.8 times longer than wide, dorsally unarmed, distoventrally with several long and slender simple setae; ischium 0.6 times basis length, 1.6 times longer than wide, dorsally unarmed, ventrally with 2 parallel rows of setae, every row with 7 groups setae and arranged in groups of 1 long filtering and 1 shorter simple seta; merus 1.5 times ischium length, 2.1 times longer than wide, dorsally unarmed, ventrally with 2 parallel rows of setae, every row with 7 groups setae and arranged in groups of 1 long filtering and 1 shorter simple seta; carpus 2.3 times merus length, 6.5 times longer than wide, with several small simple setae dorsally, ventrally with 2 parallel rows of setae, every row with 15 groups of setae and arranged in groups of 1 long filtering and 1 shorter simple seta; propodus broken off.</p> <p>Pereopod 4 (Fig. 4 B) basis 3.6 times longer than wide, dorsal margin with a big triangular tooth and scattered with several small tubercles, distoventrally with several long and slender simple setae; ischium 0.6 times basis length, 2.6 times longer than wide, dorsally unarmed, ventrally with 2 parallel rows of setae, every row with 7 groups of setae and arranged in groups of 1 long filtering and 1 shorter simple seta; merus almost as long as ischium, 2.3 times longer than wide; with 1 small simple seta distodorsally, ventrally with 2 parallel rows of setae, every row with 7 groups of setae and arranged in groups of 1 long filtering and 1 shorter simple seta; carpus 2.0 times merus length, 5.0 times longer than wide, with several small simple setae dorsally, ventrally with 2 parallel rows of setae, every row with 12 groups of setae and arranged in groups of 1 long filtering and 1 shorter simple seta; propodus about 0.9 times carpus length, 7.8 times longer than wide, with 2 moderate setae and 3 small simple setae dorsally, ventrally with 2 parallel rows of setae, every row with 11 groups of setae and arranged in groups of 1 long filtering and 1 shorter simple seta; dactylus 0.6 times propodus length, 10.0 times longer than wide, with 4 small simple setae dorsally and ventrally; unguis 1/3 times dactylus length, with a short ventral claw and a medial seta.</p> <p>Pereopod 5 (Fig. 4 C) broken off, only basis remains, 3.4 times longer than wide, with 3 feather-like setae dorsally, dorsal and ventral surface covered with extremely dense mat of fine setae.</p> <p>Pereopods 6–7 (Figs. 4 D–E) shorter and stronger than pereopods 2–4; two distal claws, stouter and much shorter than unguis of pereopods 2, 4. Pereopod 6 (Fig. 4 D) basis longest article, 3.7 times longer than wide, with 3 feather-like setae dorsally, dorsal and ventral surface covered with extremely dense mat of fine setae; ischium 0.6 times basis length, 2.3 times longer than wide, with few simple setae ventrally, dorsal and ventral surface covered with extremely dense mat of fine setae; merus 0.6 times ischium length, 1.4 times longer than wide, dorsal and ventral surface covered with extremely dense mat of fine setae, ventral surface with 2 row of short spines, each row arranged in 4 spines; carpus 0.9 times length merus, 0.8 times longer than wide, dorsal and ventral surface covered with few setules, ventral surface with 2 row of short spines, each row arranged in 4 spines; propodus 2.6 times longer than carpus, 3.3 times longer than wide, dorsal surface covered with few fine setae, ventral surface with 1 row of 7 short spines; dactylus 0.9 times propodus length, 5.0 times longer than wide, with few simple setae and several setules dorsally and ventrally; one simple seta and unguis, secondary unguis distally.</p> <p>Pereopod 7 (Fig. 4 E) basis longest article, 2.8 times longer than wide, with 3 feather-like setae dorsally, dorsal and ventral surface covered with extremely dense mat of fine setae; ischium 0.6 times basis length, 1.6 times longer than wide, with few simple setae ventrally, dorsal and ventral surface covered with extremely dense mat of setules; merus 0.8 times ischium length, 0.6 times longer than wide, dorsal and ventral surface covered with extremely dense mat of fine setae, ventral surface with 2 row of short spines, each row arranged in 4 spines; carpus 0.9 times longer than merus, 1.6 times longer than wide, dorsal and ventral surface covered with extremely dense mat of fine setae, ventral surface with 2 row of short spines, each row arranged in 4 spines; propodus 2.7 times longer than carpus, 3.6 times longer than wide, dorsal surface covered with few setules, ventral surface with 1 row of 6 short spines; dactylus 0.8 times propodus length, 4.7 times longer than wide, with few simple setae and several setules dorsally and ventrally, one simple seta and unguis, secondary unguis distally.</p> <p>Penial plate elongate (Fig. 5 B), tapering proximally and distally, unarmed.</p> <p>Pleopod 1 (Fig. 5 C) peduncle with 11 small triangular spine-like robust setae in a row laterally, ventromedially with seven coupling setae with hooked tips; exopod 1.1 times longer than endopod, 3.4 times as long as wide, laterally and apically with long plumose setae, posterior surface with transverse groove, ending with a protrusion on distal half of lateral margin; endopod with long plumose setae laterally and apically.</p> <p>Pleopod 2 (Fig. 5 D) exopod about as long as endopod, with long plumose setae laterally and apically; endopod of about same width as exopod, with long plumose setae laterally and apically; stiletto-like appendix masculina 1.1 times as long as endopod, with acute apex.</p> <p>Pleopod 3 (Fig. 5 E) exopod 1.2 times longer than endopod, setae absent; endopod of about same width as exopod, with a long and slender setae distolaterally.</p> <p>Pleopod 4 (Fig. 5 F) exopod 1.1 times longer than endopod, setae absent; endopod of about same width as exopod, with few simple setae laterally and 4 long and slender setae distolaterally.</p> <p>Pleopod 5 (Fig. 5 G) exopod 1.1 times longer than endopod, setae absent; endopod of about same width as exopod, with few simple setae laterally and 4 long and slender plumose setae distolaterally.</p> <p>Uropod (Fig. 5 A) biramous, peduncle with 14 long plumose setae on distolateral margin and a small triangular spine distally, surface laterally unarmed; exopod broader than linear endopod, about 1.3 times as long as endopod, unarmed distally; endopod with 3 simple setae distally.</p> <p> <b>Etymology.</b> The species name is derived from the oceanographic vessel “ <i>Kexue”</i> of Institute of Oceanology, Chinese Academy of Sciences, which contributed substantially to biological studies of Okinawa Trough.</p> <p> <b>Distribution and habitat.</b> Only known from type locality (Okinawa Trough, East China Sea, 2115 m).</p> <p> <b>Remarks.</b> The present new species is assigned to <i>Litarcturus</i> because of the following characters: with the tendency to reduce cuticular spines on the whole body surface; cephalothorax with one pair of supraocular spines, in some cases reduced or very small; caudal pleotelsonic spines comparatively short.</p> <p> <i>Litarcturus kexueiae</i> <b>sp. nov.</b> belongs to the third group with <i>L. granulosus</i> (Nordenstam, 1933) and <i>L. stebbingi</i> (Beddard, 1886), with supraocular and caudal pleotelsonic spines. However, <i>L. kexueiae</i> <b>sp. nov.</b> differs markedly from <i>L. granulosus</i> as its supraocular spines are longer than the cephalothorax apex (versus supraocular spines not longer than the cephalothorax apex), and from <i>L. stebbingi</i> as its caudal pleotelsonic spines are longer than the pleotelson apex (versus caudal pleotelsonic spines not longer than the pleotelson apex).</p>Published as part of <i>Liu, Wenliang & Sha, Zhongli, 2015, Litarcturus kexueiae sp. nov., a new deep-sea isopod from the Okinawa Trough (Crustacea, Isopoda, Valvifera, Antarcturidae), pp. 531-540 in Zootaxa 4013 (4)</i> on pages 533-539, DOI: 10.11646/zootaxa.4013.4.4, <a href="http://zenodo.org/record/236981">http://zenodo.org/record/236981</a>
Caracladus montanus Sha & Zhu 1994
No full text<i>Caracladus montanus</i> Sha & Zhu, 1994 <p> <i>Caracladus montanus</i> Sha & Zhu, 1994: 172, figs 1–7; Song <i>et al.</i> 1999: 160, figs 88M–O.</p> <p> <b>Type material.</b> <b>HOLOTYPE: China:</b> <i>Jilin:</i> Changbai mountain [42°00' N, 128°01' E], 1♂ 1979-1990 (Sha & Zhu 1994). <b>PARATYPES: China:</b> <i>Jilin:</i> Changbai mountain, Baiyunfeng (“white cloud peak”) [42°00' N, 128°01' E], 1♂ 19.vi.1979, leg. Y. Zhang and C. Wang (Sha & Zhu 1994); Changbai mountain [42°00' N, 128°01' E], 1♂ 11.viii.1985, leg. C. Zhu (Sha & Zhu 1994); Changbai mountain, Xidapo (“big western slope”) [42°00' N, 128°01' E], 6♂ 9♀ 31.vii.1990, leg. Y. Sha (Sha & Zhu 1994); Changbai mountain, Xiaotianchi (“small heaven lake”) [42°05'48'' N, 128°03'50'' E], 3♂ 5♀ 04.viii.1990, leg. Y. Sha (Sha & Zhu 1994). The type material (mentioned above) is stored in the Department of Biology, Norman Bethune University of Medical Sciences in Changchun, which is now a subunit of the Jilin University, China (Sha & Zhu 1994). The material was not available for observation since establishing contacts with Jilin University was not successful..</p> <p> <b> Diagnosis. <i>Males</i></b> : Similar to <i>C. tsurusakii</i> with differences in the shape of the male palpal tibia and the embolus (Sha & Zhu 1994). In lateral view, the cephalic lobe is broadest below the eye-field (Sha & Zhu 1994: Fig. 2), but is narrowed down in <i>C. tsurusakii</i> (Fig. 45). The prolateral tibialapophysis looks like a big tooth (Sha & Zhu 1994: Fig. 4) whereas it is a glabrous blunt apophysis in <i>C. tsurusakii</i> (Fig. 42).</p> <p> <i>Females</i>: The shape of the epigynum and the vulva are different to what is seen in other <i>Caracladus</i> species. E.g. the curled copulatory duct (Sha & Zhu 1994: Fig. 7).</p> <p> <b> Description. <i>Males</i></b> : Total length: 1.85–2.07 mm (Sha & Zhu 1994). Cephalic lobe: facing forward, hairy in front of the PME (Sha & Zhu 1994: Fig. 2); shaft rather thick with some hairs (Sha & Zhu 1994: Fig. 2); sulcus absent. Eyes: PME upmost on the cephalic lobe (Sha & Zhu 1994: Fig. 2). Chelicerae: promargin with five larger teeth; retromargin with five very small denticles; stridulatory striae present (Sha & Zhu 1994). Legs: tibia I–IV with one dorsal proximal macroseta (1-1-1-1); Tm I: 0.61 (Sha & Zhu 1994). Pedipalp: paracymbium simple hook (Sha & Zhu 1994: Fig. 3); retrolateral tibial apophysis small tooth; prolateral tibial apophysis long and broad (Sha & Zhu 1994: Figs 4, 5); protegulum present (Sha & Zhu 1994: Fig. 3).</p> <p> <i>Females</i>: General appearance similar to males but without a cephalic lobe (Sha & Zhu 1994). Total length: 2.07–2.72 mm (Sha & Zhu 1994). Eyes: anterior row slightly recurved (Sha & Zhu 1994). Chelicerae: stridulatory striae present (Sha & Zhu 1994). Epigyne: ventral plate hourglass-like, visible in ventral view (Sha & Zhu 1994: Fig. 6, see remarks). Vulva: receptacula globular; copulatory duct spiral (Sha & Zhu 1994: Fig. 7).</p> <p> <b>Distribution.</b> Only known from the type locality in Jilin, China (Song <i>et al.</i> 1999).</p> <p> <b>Habitat.</b> The coordinates in the original publication correspond to a spot at ca. 2000 m a.s.l.</p> <p> <b>Phenology.</b> All records in summer time between June and August.</p> <p> <b>Remarks.</b> No specimens were available for examination. The diagnosis and description of certain structures and the coding of characters for the phylogeny on species level followed the descriptions and figures given in Sha and Zhu (1994) of which some are redrawn in Song <i>et al.</i> (1999). Misinterpretations of the figures can therefore not be excluded. It is assumed, for example, that <i>C. montanus</i> has no sulcus because Sha and Zhu (1994) mention the close resemblance to <i>C. tsurusakii</i> without mentioning a sulcus in the original description. The conformation of the epigyne is unclear to the authors. It is assumed that the ventral hourglassshaped structure represents the dorsal plate.</p>Published as part of <i>Frick, Holger & Muff, Patrick, 2009, Revision of the genus Caracladus with the description of Caracladus zamoniensis spec. nov. (Araneae, Linyphiidae, Erigoninae), pp. 1-37 in Zootaxa 1982</i> on page 17, DOI: <a href="http://zenodo.org/record/185321">10.5281/zenodo.185321</a>
Frankfurt book fair: cancelled prize ceremony for Palestinian author is part of a long history of political zigzagging
No full textFirst paragraph: The Frankfurt Buchmesse, or book fair, is the world’s largest publishing industry gathering, attracting thousands of exhibitors every October. On one level, it’s a business event focused on creating buzz for forthcoming bestsellers, trading rights and discussing industry developments. On another, it’s a public celebration of books and the values associated with them.https://theconversation.com/frankfurt-book-fair-cancelled-prize-ceremony-for-palestinian-author-is-part-of-a-long-history-of-political-zigzagging-21574
On the Security of HMAC and NMAC Based on HAVAL, MD4, MD5, SHA-0 and SHA-1
No full textHMAC is a widely used message authentication code and a pseudorandom function generator based on cryptographic hash functions such as MD5 and SHA-1. It has been standardized by ANSI, IETF, ISO and NIST. HMAC is proved to be secure as long as the compression function of the underlying hash function is a pseudorandom function. In this paper we devise two new distinguishers of the structure of HMAC, called differential and rectangle distinguishers, and use them to discuss the security of HMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1. We show how to distinguish HMAC with reduced or full versions of these cryptographic hash functions from a random function or from HMAC with a random function. We also show how to use our differential distinguisher to devise a forgery attack on HMAC. Our distinguishing and forgery attacks can also be mounted on NMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1.status: Publishe
SHA-RV: A RISC-V Accelerator for SHA-224/256 with Cycle Reduced ISA Extensions for Blockchain Applications
No full textThe Secure Hash Algorithm SHA-256 and SHA-224 are widely used for software integrity, digital signatures, and blockchain across embedded and edge platforms. Prior RISC-V accelerators still struggle to achieve low cycle counts and high system throughput on long message streams. This paper proposes a hardware-efficient RISC-V accelerator with low-latency SHA instruction extensions, named SHA-RV, to reduce cycles and improve end-to-end performance. SHA-RV integrates three optimizations: a high-bandwidth BufferSet for continuous data supply, a four-stage pipelined SHA core, a system-level double-buffering pipeline, and an FSM-orchestrated BufferSet mapping. Implemented on a Xilinx ZCU102 system on a chip, SHA-RV operates at up to 300 MHz and uses 3,146 flip-flops, 5,175 lookup tables, and 15 block RAMs. On 64-byte blocks, SHA-RV completes a block in 257 cycles, improving over related RISC-V designs by between 9.7 and 134.9 times, while reducing logic resources versus the ISOCC 2024 design by 89.4 percent in flip-flops and 85.2 percent in lookup tables. At the system level, SHA-RV achieves a throughput of 599 megabits per second and an energy efficiency of 798.7 megabits per second per watt under a real-time dynamic power assumption of 0.75 watts, outperforming representative CPUs by between 61 and 454 times in energy efficiency. These results show lower latency and superior hardware efficiency relative to prior work
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