waashk/dblp huggingface dataset:
double-base number system for multi-scalar multiplications. the joint sparse form is currently the standard representation system to perform multi-scalar multiplications of the form [n]p + m[q]. we introduce the concept of joint double-base chain, a generalization of the double-base number system to represent simultaneously n and m. this concept is relevant because of the high redundancy of double-base systems, which ensures that we can find a chain of reasonable length that uses exactly the same terms to compute both n and m. furthermore, we discuss an algorithm to produce such a joint double-base chain. because of its simplicity, this algorithm is straightforward to implement, efficient, and also quite easy to analyze. namely, in our main result we show that the average number of terms in the expansion is less than 0.3945log2 n. with respect to the joint sparse form, this induces a reduction by more than 20% of the number of additions. as a consequence, the total number of multiplications required for a scalar multiplications is minimal for our method, across all the methods using two precomputations, p + q and p ¿ q. this is the case even with coordinate systems offering very cheap doublings, in contrast with recent results on scalar multiplications. several variants are discussed, including methods using more precomputed points and a generalization relevant for koblitz curves. our second contribution is a new way to evaluate $\widehat\phi$, the dual endomorphism of the frobenius. namely, we propose formulae to compute $\pm{\widehat\phi}(p)$ with at most 2 multiplications and 2 squarings in the base field $\mathbb{f}_{2^d}$. this represents a speed-up of about 50% with respect to the fastest known techniques. this has very concrete consequences on scalar and multi-scalar multiplications on koblitz curves.
cube attacks on tweakable black box polynomials. almost any cryptographic scheme can be described by tweakable polynomials over gf(2), which contain both secret variables (e.g., key bits) and public variables (e.g., plaintext bits or iv bits). the cryptanalyst is allowed to tweak the polynomials by choosing arbitrary values for the public variables, and his goal is to solve the resultant system of polynomial equations in terms of their common secret variables. in this paper we develop a new technique (called a cube attack) for solving such tweakable polynomials, which is a major improvement over several previously published attacks of the same type. for example, on the stream cipher trivium with a reduced number of initialization rounds, the best previous attack (due to fischer, khazaei, and meier) requires a barely practical complexity of 255 to attack 672 initialization rounds, whereas a cube attack can find the complete key of the same variant in 219 bit operations (which take less than a second on a single pc). trivium with 735 initialization rounds (which could not be attacked by any previous technique) can now be broken with 230 bit operations. trivium with 767 initialization rounds can now be broken with 245 bit operations, and the complexity of the attack can almost certainly be further reduced to about 236 bit operations. whereas previous attacks were heuristic, had to be adapted to each cryptosystem, had no general complexity bounds, and were not expected to succeed on random looking polynomials, cube attacks are provably successful when applied to random polynomials of degree d over n secret variables whenever the number m of public variables exceeds d + log d n. their complexity is 2 d ¿ 1 n + n 2 bit operations, which is polynomial in n and amazingly low when d is small. cube attacks can be applied to any block cipher, stream cipher, or mac which is provided as a black box (even when nothing is known about its internal structure) as long as at least one output bit can be represented by (an unknown) polynomial of relatively low degree in the secret and public variables.
a unified framework for the analysis of side-channel key recovery attacks. the fair evaluation and comparison of side-channel attacks and countermeasures has been a long standing open question, limiting further developments in the field. motivated by this challenge, this work makes a step in this direction and proposes a framework for the analysis of cryptographic implementations that includes a theoretical model and an application methodology. the model is based on commonly accepted hypotheses about side-channels that computations give rise to. it allows quantifying the effect of practically relevant leakage functions with a combination of information theoretic and security metrics, measuring the quality of an implementation and the strength of an adversary, respectively. from a theoretical point of view, we demonstrate formal connections between these metrics and discuss their intuitive meaning. from a practical point of view, the model implies a unified methodology for the analysis of side-channel key recovery attacks. the proposed solution allows getting rid of most of the subjective parameters that were limiting previous specialized and often ad hoc approaches in the evaluation of physically observable devices. it typically determines the extent to which basic (but practically essential) questions such as "how to compare two implementations?" or "how to compare two side-channel adversaries?" can be answered in a sound fashion.
optimal randomness extraction from a diffie-hellman element. in this paper, we study a quite simple deterministic randomness extractor from random diffie-hellman elements defined over a prime order multiplicative subgroup g of a finite field ${\mathbb z}_p$ (the truncation), and over a group of points of an elliptic curve (the truncation of the abscissa). informally speaking, we show that the least significant bits of a random element in $g\subset {\mathbb z}_p^*$ or of the abscissa of a random point in $\mathcal{e}({\mathbb f}_p)$ are indistinguishable from a uniform bit-string. such an operation is quite efficient, and is a good randomness extractor, since we show that it can extract nearly the same number of bits as the leftover hash lemma can do for most elliptic curve parameters and for large subgroups of finite fields. to this aim, we develop a new technique to bound exponential sums that allows us to double the number of extracted bits compared with previous known results proposed at icalp'06 by fouque et al. it can also be used to improve previous bounds proposed by canetti et al. one of the main application of this extractor is to mathematically prove an assumption proposed at crypto '07 and used in the security proof of the elliptic curve pseudo random generator proposed by the nist. the second most obvious application is to perform efficient key derivation given diffie-hellman elements.
possibility and impossibility results for encryption and commitment secure under selective opening. the existence of encryption and commitment schemes secure under selective opening attack (soa) has remained open despite considerable interest and attention. we provide the first public key encryption schemes secure against sender corruptions in this setting. the underlying tool is lossy encryption. we then show that no non-interactive or perfectly binding commitment schemes can be proven secure with black-box reductions to standard computational assumptions, but any statistically hiding commitment scheme is secure. our work thus shows that the situation for encryption schemes is very different from the one for commitment schemes.
single-symbol ml decodable distributed stbcs for partially-coherent cooperative networks. a relay network with n relays and a single source-destination pair is called a partially-coherent relay channel (pcrc) if the destination has perfect channel state information (csi) of all the channels and the relays have only the phase information of the source-to-relay channels. in this paper, first, a new set of necessary and sufficient conditions for a space-time block code (stbc) to be single-symbol decodable (ssd) for co-located multiple antenna communication is obtained. then, this is extended to a set of necessary and sufficient conditions for a distributed stbc (dstbc) to be ssd for a pcrc. using this, several ssd dstbcs for pcrc are identified. it is proved that even if a ssd stbc for a co-located mimo channel does not satisfy the additional conditions for the code to be ssd for a pcrc, single-symbol decoding of it in a pcrc gives full-diversity and only coding gain is lost. it is shown that when a dstbc is ssd for a pcrc, then arbitrary coordinate interleaving of the in-phase and quadrature-phase components of the variables does not disturb its ssd property for pcrc. finally, it is shown that the possibility of channel phase compensation operation at the relay nodes using partial csi at the relays increases the possible rate of ssd dstbcs from 2/n when the relays do not have csi to 1/2, which is independent of n.
two-user opportunistic scheduling using hierarchical modulations in wireless networks with heterogenous average link gains. our contribution, in this paper, is two-fold. first, we analyze the performance of a hierarchical modulation-assisted two-best user opportunistic scheduling (tbs) scheme, which was proposed by the authors, in a fading environment where different users have different average link gains. specifically, we present a new expression for the spectral efficiency (se) of the users and using this expression, we compare the degrees of fairness (dof) of the tbs scheme with that of classical single user opportunistic scheduling schemes, namely, absolute carrier-to-noise ratio (cnr) based single-best user scheduling (sbs) and normalized cnr based proportional fair scheduling (pfs) schemes. the second contribution is that we propose a new hybrid two-user opportunistic scheduling (hts) scheme based on our earlier proposed tbs scheme. this hts scheme selects the first user based on the largest absolute cnr value among all the users while the second user is selected based on the ratios of the absolute cnrs to the corresponding average cnrs of the remaining users. the total transmission rate i.e., the constellation size is selected according to the absolute cnr of the first best user. the total transmission rate is then allocated among these selected users by joint consideration of their absolute cnrs and allocated number of information bit(s) are transmitted to them using hierarchical modulations. numerical results are presented for a fading environment where different users experience independent but non-identical (i.n.d.) channel fading. these selected numerical results show that the proposed hts scheme can considerably increase the system's fairness without any degradation of the link spectral efficiency (lse) i.e., the multiuser diversity gain compared to the classical sbs scheme. these results also show that the proposed hts scheme has a lower fairness in comparison to the pfs scheme which suffers from a considerable degradation in lse.
on the performance analysis of composite multipath/shadowing channels using the g-distribution. composite multipath fading/shadowing environments are frequently encountered in different realistic scenarios. these channels are generally modeled as a mixture of nakagamim multipath fading and log-normal shadowing. the resulting composite probability density function (pdf) is not available in closed form, thereby making the performance evaluation of communication links in these channels cumbersome. in this paper, we propose to model composite channels by the g- distribution. this pdf arises when the log-normal shadowing is substituted by the inverse-gaussian one. this substitution will prove to be very accurate for several shadowing conditions. in this paper we conduct a performance evaluation of single-user communication systems operating in a composite channel. our study starts by deriving an analytical expression for the outage probability. then, we derive the moment generating function of the g-distribution, hence facilitating the calculation of average bit error probabilities. we also derive analytical expressions for the channel capacity for three adaptive transmission techniques, namely, i) optimal rate adaptation with constant power, ii) optimal power and rate adaptation, and iii) channel inversion with fixed rate.
an autonomic service delivery platform for service-oriented network environments. in this paper, we propose a novel autonomic service delivery platform for service-oriented network environments. the platform enables a self-optimizing infrastructure that balances the goals of maximizing the business value derived from processing service requests and the optimal utilization of it resources. we believe that our proposal is the first of its kind to integrate several well-established theoretical and practical techniques from networking, microeconomics, and service-oriented computing to form a fully distributed service delivery platform. the principal component of the platform is a utility-based cooperative service routing protocol that disseminates congestion-based prices among intermediaries to enable the dynamic routing of service requests from consumers to providers. we provide the motivation for such a platform and formally present our proposed architecture. we discuss the underlying analytical framework for the service routing protocol, as well as key methodologies which together provide a robust framework for our service delivery platform that is applicable to the next-generation of middleware and telecommunications architectures. we discuss issues regarding the fairness of service rate allocations, as well as the use of nonconcave utility functions in the service routing protocol. we also provide numerical results that demonstrate the ability of the platform to provide optimal routing of service requests.
qrd-based precoded mimo-ofdm systems with reduced feedback. qr decomposition (qrd)-based precoded mimo-ofdm systems with reduced feedback are proposed to convert the mimo-ofdm channel into layered subchannels. qrd-m is further combined with either singular value (svd) or geometric mean decomposition (gmd) of the time-domain channel impulse response matrix. as a result, the receiver in the proposed systems only needs to feed back information describing one precoding matrix for all carriers. simulation results confirm the bit-error-rate (ber) and throughput performance superiority of the proposed systems compared to conventional svd per-carrier precoding schemes.
underwater acoustic sensor networks: target size detection and performance analysis. underwater acoustic sensor network consists of a variable number of sensors and vehicles that are deployed to perform collaborative monitoring tasks over a given area. scalability concern suggests a hierarchical organization of underwater sensor networks with the lowest level in the hierarchy being a cluster. in this paper, we show that an ultra-wide band (uwb) channel can be used for underwater channel modeling and propose a maximum-likelihood (ml) estimation algorithm for underwater target size detection using collaborative signal processing within a cluster in underwater acoustic sensor networks. theoretical analysis demonstrates that our underwater sensor network can tremendously reduce the variance of target size estimation. we show that our ml estimator is unbiased and the variance of parameter estimation matches the cramer-rao lower bound. simulations further validate these theoretical results.
sum-rate analysis of multiuser mimo system with zero-forcing transmit beamforming. in this letter, we present the exact sum-rate analysis of the multiuser multiple-input multiple-output (mimo) systems with zero-forcing transmit beamforming (zfbf). we develop the analytical expressions of the ergodic sum-rate for two low-complexity user selection strategies for the dual-transmitantenna scenario. based on the analytical results, we examine the parameter optimization problem to properly trade off between channel power gain and directional gain in term of maximizing the ergodic sum rate.
distributed space-time coding for two-way wireless relay networks. in this paper, we consider distributed space-time coding for two-way wireless relay networks, where communication between two terminals is assisted by relay nodes. relaying protocols using two, three, and four time slots are proposed. the protocols using four time slots are the traditional amplify-and-forward (af) and decode-and-forward (df) protocols, which do not consider the property of the two-way traffic. a new class of relaying protocols, termed as partial decode-and-forward (pdf), is developed for the two time slots transmission, where each relay first removes part of the noise before sending the signal to the two terminals. protocols using three time slots are proposed to compensate the fact that the two time slots protocols cannot make use of direct transmission between the two terminals. for all protocols, after processing their received signals, the relays encode the resulting signals using a distributed linear dispersion (ld) code. the proposed af protocols are shown to achieve the diversity order of min {n, k} (1-(log log p/log p), where n is the number of relays, p is the total power of the network, and k is the number of symbols transmitted during each time slot. when random unitary matrix is used for ld code, the proposed pdf protocols resemble random linear network coding, where the former operates on the unitary group and the latter works on the finite field. moreover, pdf achieves the diversity order of min {n, k} but the conventional df can only achieve the diversity order of 1. finally, we find that two time slots protocols also have advantages over four-time-slot protocols in media access control (mac) layer.
an analytical method for calculating the bit error rate performance of rake reception in uwb multipath fading channels. the bit error rate performance of rake reception of impulse radio ultra-wide bandwidth signals over the ieee 802.15.3a channel models is evaluated. instead of using gaussian approximation for the probability density function of the total disturbance which includes the multi-user interference and the background additive white gaussian noise, two new models dubbed the "composite lognormal-gaussian" and the "composite lognormal-laplacian" are proposed for modeling the multi-user interference and shadowing in ultra-wide bandwidth multipath fading channels. tractable formulae for bit error rate evaluation of rake reception in ultra-wide bandwidth multipath channels are derived for both models. numerical results indicate that these formulae predict the bit error rate performance with good accuracy, and can be rapidly and easily evaluated using commonplace computer resources.
joint connection admission control and routing in ieee 802.16-based mesh networks. connection admission control and routing are two important mechanisms in the provision of quality of service (qos) in ieee 802.16-based wireless mesh networks. in this paper, we propose a joint admission control and routing scheme for multiple service classes with the objective to maximize the overall revenue from all carried connections. qos constraints such as handoff dropping probability can be guaranteed. multiple service classes can be prioritized by imposing different reward rates. we formulate the problem as a decision process, and apply optimization techniques to obtain the optimal admission control policies. the effectiveness of the proposed approach is illustrated by numerical and simulation results. we show that the proposed joint admission control and routing scheme can produce maximum revenue obtainable by the system under qos constraints.we also show that the optimal joint admission control policy is a randomized policy, i.e., connections are admitted to the system with some probabilities when the system is in some states.
a collision-free mac scheme for multimedia wireless mesh backbone. wireless mesh networking is a promising wireless technology for future broadband internet access. in this paper, a novel collision-free medium access control (mac) scheme supporting multimedia applications is proposed for wireless mesh backbone. the proposed scheme is distributed, simple, and scalable. benefiting from the fixed locations of wireless routers, the proposed mac scheme reduces the control overhead greatly as compared with conventional contention-based mac schemes (e.g., ieee 802.11). in addition, the proposed scheme can provide guaranteed priority access to real-time traffic and, at the same time, ensure fair channel access to the routers with data traffic. unlike most of the existing mac schemes which focus on single-hop transmissions, the proposed mac scheme takes the intra-flow correlations between up-stream and downstream hops of a multi-hop flow into consideration. to avoid buffer overflow at bottleneck routers, a simple but effective congestion control mechanism is proposed. simulation results demonstrate that the proposed scheme significantly improves the delay performance of real-time traffic and the end-to-end data throughput, as compared with ieee 802.11 and distributed packet reservation multiple access (dprma). the performance analysis of the proposed scheme is also presented. the accuracy of the analytical results is verified by computer simulations.
blind cooperative diversity using distributed space-time coding in block fading channels. mobile users with single antennas can still take advantage of spatial diversity through cooperative space-time encoded transmission. in this paper, we consider a scheme in which a relay chooses to cooperate only if its source-relay channel is of an acceptable quality and we evaluate the usefulness of relaying when the source acts blindly and ignores the decision of the relays whether they may cooperate or not. in our study, we consider the regenerative relays in which the decisions to cooperate are based on a signal-to-noise ratio (snr) threshold and consider the impact of the possible erroneously detected and transmitted data at the relays. we derive the end-to-end bit-error rate (ber) expression and its approximation for binary phase-shift keying modulation and look at two power allocation strategies between the source and the relays in order to minimize the end-to-end ber at the destination for high snr. some selected performance results show that computer simulations based results coincide well with our analytical results.
cognitive network access using fuzzy decision making. we consider a scenario in which wireless users want to connect to the internet using one of several available network access opportunities, possibly using different radio technologies. we propose a distributed cognitive network access scheme with the aim of providing the best quality of service with respect to both radio link and core network performance and user application requirements. knowledge of the service quality experienced by active connections is shared, and prospective users use fuzzy logic techniques to process cross-layer communication quality metrics and to estimate the expected transport-layer performance. these estimates are compared to the quality of service requirements of the application using fuzzy decision making techniques to choose the most suitable access opportunity. this scheme naturally fits into the recently proposed cognitive network paradigm in that it defines a cognition process leveraging on end-to-end and cross-layer performance evaluation techniques as well as information sharing among users; moreover, it offers a significant amount of flexibility and extensibility, thanks to its modularity and its independence from the particular technology and application being used. the proposed scheme is shown to outperform state-of-the-art solutions in several multitechnology and multi-application scenarios, while at the same time achieving similar performance to application-specific omniscient schemes that we introduce in this paper as a benchmark.