Abstract: This work presents an adaptive profitable discriminatory pricing mechanism for cloud computing based on secure function decomposition, cryptographic commitments and zero knowledge proof. Cloud computing is an emerging trend of enterprise resource planning where a selling agent or service provider (S) wants to allocate a set of computational resources and related IT services optimally and fairly among many buying agents or service consumers (B) within its capacity constraint. Each service consumer discloses its demand plan for an IT portfolio within its budget constraint and rank of preference. An IT portfolio may include SaaS, PaaS, IaaS, CaaS, DaaS and dSaaS. The basic objective of the service provider is to optimize its expected revenue within target profit margin. It is basically a problem of secure function evaluation where the concept of decomposition of a function is considered. It is a constrained nonlinear optimization problem; the search is governed by a set of intelligent moves. The communication complexity of the pricing mechanism depends on the time constraint of the negotiating agents, their information state and the number of negotiation issues; it also depends on number of negotiation rounds and the complexity of IT portfolio. The computational cost depends on the complexity of function decomposition. The security and privacy of strategic data of the trading agents provides business intelligence to the pricing mechanism. The ultimate objective of the mechanism is to predict a profitable discriminatory pricing plan for each consumer.
cAMP signaling and the control of Schwann cell fate: The ubiquitous second messenger cyclic adenosine monophosphate (cAMP) controls a variety of cellular responses in a cell type-specific and stimulus-dependent manner through an elaborate network of signaling intermediaries that connect stimulation of cell membrane receptors (typically G protein-coupled receptors, GPCRs) to transcription factor activation. Schwann cells (SCs) are highly responsive to cAMP throughout their lifespan, as extensive research has shown that SC survival, lineage specification, proliferation and differentiation into myelin-forming cells require cAMP signaling. The first evidence concerning the relevance of cAMP to SC function was documented in the 1970s with the discovery that mitotic cell division of isolated SCs was enhanced by cAMP-stimulating agents. Further mechanistic studies indicated that cAMP acts together with growth factors such as neuregulin to synergistically increase the rate of S-phase entry. In addition, cAMP has been known since the 1980s to directly drive the expression of proteins and lipids specific to the myelin sheath, including protein zero, periaxin, myelin associated glycoprotein (MAG) and galactocerebroside (Jessen et al., 1991). Yet, it was not until recent years that the molecular basis of cAMP-mediated signal transduction in SCs began to be understood. As described below, emerging data from independent in vitro and in vivo approaches have highlighted the identity of some key molecular players operating both upstream and downstream of cAMP biosynthesis that act in conjunction with other signals to differentially control SC proliferation and differentiation. It is understood that myelination in SCs is an inducible process sensitive to extracellular signals. Whereas oligodendrocytes autonomously turn on the expression of myelin-related genes upon or even when deprived of axon contact, SCs tend to remain indefinitely undifferentiated despite maintaining extensive contact with axons. Examples provided by in vitro myelination studies and models of nerve regeneration in vivo have shown that some SCs may effectively extend their processes along those of axons and form a basal lamina, a pre-requisite for myelination, yet still do not proceed to form a myelin sheath. If axon contact is not sufficient for myelination, what are the factors limiting the process? In a recent study, we argued that one such factor is cAMP, as activation of cAMP signal transduction in SCs is sufficient to bundle and synchronize the differentiating responses of axon-associated SCs in such a way as to accelerate and greatly enhance myelin formation in vitro (Bacallao and Monje, 2015). By promoting the transition from an immature (proliferative) to a differentiated (growth arrested) state, cAMP acts in concert with, but still independently of, other axonal signals such as neuregulin to initiate myelin membrane wrapping. Indeed, cAMP seems to function as an on/off control switch for myelination, as the simple removal of the cAMP stimulus is sufficient to readily suppress the expression of myelin-associated genes and shift the SC's phenotype back to an immature proliferative state that resembles the one derived through dedifferentiation in response to nerve injury (Monje et al., 2010). Though at first glance it may seem contradictory to assert that a single second messenger could positively control proliferation and differentiation, a specific cellular outcome is achieved via the use of distinct and independent signaling mechanisms (Figure 1A). Whereas the synergistic effect of cAMP on SC proliferation is achieved through gating or cross-talk with signals emanating from ligand-activated receptor tyrosine kinases such as neuregulin-activated ErbB/HER receptors (Monje et al., 2008), the effect of cAMP on differentiation is direct and seems not to require the concurrent activation of receptor tyrosine kinase pathways. The use of separate transduction elements also contributes to the specificity of outcome. As such, SC proliferation rather than differentiation relies on the activation of the transmembrane adenylyl cyclase (tmAC)-dependent, protein kinase A (PKA)-dependent pathway. SC myelination, by contrast, seems to be controlled by non-canonical cAMP signaling, as this process is mediated by effectors and upstream activators that have been relatively understudied in comparison to the classical tmAC-PKA pathway. Novel transduction elements reported to control myelination include: (1) the exchange protein activated by cAMP (EPAC), which is a guanine nucleotide exchange factor for the small GTP-binding protein Rap1 and transduces cAMP signals through direct binding to cAMP (Bacallao and Monje, 2013); (2) the soluble adenylyl cyclase (sAC), which is an ubiquitous forskolin- and GPCR-insensitive adenylyl cyclase subtype that generates cAMP in various cell compartments (Bacallao and Monje, 2015); and (3) the adhesion receptor Gpr126, which is a highly conserved orphan GPCR that signals via G protein activation and cAMP to control myelination in vivo (Mogha et al., 2013). These signal transduction molecules represent attractive targets to control the state of differentiation that is conducive to myelination independently of the control of proliferation.Figure 1: Balancing Schwann cell (SC) fate via cyclic adenosine monophosphate (cAMP).A mechanistic model for the differential control of SC proliferation and differentiation by cAMP signals based on available data (A) and a suggested general strategy for otimizing cAMP-mediated, SC-dependent regeneration and myelination (B). Krox-20, a cAMP-dependent transcription factor that is a master regulator of myelination; O1: The myelin lipid galactocerebroside; EPAC: exchange protein activated by cAMP; GPCR: G protein-coupled receptor; PKA: protein kinase A; sAC: soluble adenylyl cyclase; tmAC: transmembrane adenylyl cyclase.Manipulating and optimizing cAMP signaling in SCs for therapeutic applications: Our improved understanding of cAMP regulation of SC fate, along with the well-recognized role of cAMP in promoting axon growth in different types of neurons (Spencer and Filbin, 2004), can be exploited to delineate novel approaches to improve the outcome of SC-mediated nerve repair. The basic argument discussed herein postulates that balancing proliferation and differentiation through differential targeting of the cAMP signaling system may have an impact on the extent to which endogenous or transplanted SCs promote peripheral and central axon regeneration and myelination, thus contributing to functional repair. SCs have been grafted in the injured or dysmyelinated CNS and PNS for decades on the assumption that they can foster axon growth and subsequently form a myelin sheath to insulate regenerated and/or spared axons. Because the benefits of SC transplantation can be improved significantly if additional treatments are provided, attempts have been made to combine SC transplants with modulators of intracellular cAMP levels to augment nervous tissue repair (Fortun et al., 2009). One advantage of targeting the cAMP signaling system is that a single therapeutic approach can potentially improve various aspects linked to functional repair. Another advantage is that many of the molecular players within this system lend themselves suitable to pharmacological intervention; in addition, extensive information is available on their mechanism of action at the cellular and molecular levels. Considering the sophistication of cAMP networks, the potential for cross-talk, and the multiple cellular targets that are expected to react to cAMP stimulation, one may reason that any given cAMP therapy should be tailored to a desired cellular outcome. Most studies performed so far have relied on the use of broad-spectrum cAMP-stimulating agents administered either locally or systemically [see (Knott et al., 2014) for a recent review]. Though useful for proof of principle and feasibility assessment, this type of traditional approach may limit our understanding of the mechanism of action by which a given treatment promotes repair. An example is provided by a SC transplantation study in the contused spinal cord which showed a dramatic increase in axon growth and myelination within the SC transplants upon co-administration of dibutyryl-cAMP (a non-hydrolyzable cAMP analog) and rolipram (a phosphodiesterase, PDE, IV inhibitor); yet, whether the effect of cAMP was mediated by the SCs, the neurons or both could not be defined simply on the basis of the results obtained (Pearse et al., 2004). The implementation of a cAMP-based strategy designed to modulate the rate and/or extent of myelin formation by SCs, alone or while concurrently preventing myelin loss, seem in principle rather straightforward based on our current knowledge on how the initiation and maintenance of myelination is controlled by cAMP. Yet, a strategy for SC-mediated nerve repair is more challenging, as treatment should balance at least two independent events: (1) promotion of axonal growth, which can be achieved by targeting cAMP-dependent pathways within the SCs and/or the neurons; and (2) promotion of myelination, which can be achieved by targeting pathways within the SCs. Novel research in the SC field has suggested that axon regeneration and SC differentiation are highly interdependent events (Jessen and Mirsky, 2008). Whereas the initiation and maintenance of an immature SC phenotype may foster axon growth, a premature or exacerbated differentiation of the SC may determine a poor or suboptimal regenerative response. The axon growth-promoting benefits of the SCs themselves are expected to be reduced upon their differentiation into myelin-forming cells. Not only do SCs cease to proliferate, migrate and secrete neurotrophic factors as they undergo differentiation, but the expression of myelin-specific proteins such as MAG on their surface may elicit a stop signal for axonal growth, a phenomenon which is particularly relevant in the context CNS regeneration. The present line of reasoning implies that several independent parameters should be considered when optimizing cAMP therapies for SC-mediated repair and myelination. These parameters include: (1) the properties and specificity of the cAMP-inducing treatment on downstream effectors, (2) the possibility of positive or negative cross-talk of cAMP signaling with other pathways; (3) the timing of administration and the duration of the cAMP stimulus; (4) the expected cell type-specific outcome of cAMP elevation in SCs and neurons; and (5) the effect of environmental or context-specific factors. Multiple tools currently available offer an exceptional opportunity to fine-tune cAMP signaling into a desired cellular outcome. Selective targeting and specificity of signaling is plausible if we understand that cAMP does not act as a unitary signaling pathway but orchestrates many differentially regulated pathways that are built around a common second messenger. First generation cAMP-modulating agents, which offered low or little power for target discrimination, can nowadays be replaced by the wide range of chemical agents (activators and inhibitors) with potential to distinguish among distinct cAMP-specific PDEs, adenylyl cyclase subtypes and downstream cAMP effectors. Novel pathway-specific, cell permeable cAMP derivatives offer the possibility to potently and selectively manipulate PKA and EPAC activation within living cells (Holz et al., 2008). We and others have used some of these analogs to more selectively control the rate of proliferation (via PKA) and differentiation (via EPAC) of SCs in vitro. Isoform-specific EPAC antagonists have also become available, which brings the unique potential to block EPAC signaling while maintaining PKA-initiated pathways. Differential targeting of tmAC and sAC activities can also provide a feasible route for selective pathway modulation based on their clearly different modes of activation and inhibition. Non-pharmacological treatments such as electrical stimulation, which is known to stimulate sAC, may contribute to modulating the potency and pathway specificity through cAMP in selected cell populations. In optimizing the timing and duration of treatment, one should consider that SC differentiation may counterbalance axon growth. Thus, cAMP therapies aimed to increase myelination may be better implemented independently of those aimed to increase axon regeneration or alternatively, during the later stages of the regeneration process. Additive or synergistic effects on SC-mediated axon regeneration may be achieved if treatments aimed at enhancing SC proliferation (by targeting SCs) are coupled to those aimed at enhancing axon growth (by targeting the neurons) as long as these are provided while concurrently halting or delaying SC differentiation (Figure 1B). A faster or more efficient myelination may be derived from the synchronization of the differentiating responses expected to result from cAMP elevation in SCs, if a similar phenomenon is observed during nerve development or repair in vivo. Despite no evidence so far indicates that the environment per se would preclude cAMP-induced SC proliferation and/or differentiation, the scenarios may differ considerably in light of the expected effects of cAMP on axon regeneration in PNS and CNS neurons. To conclude, our significantly expanded understanding of cAMP signal transduction in SCs offers a unique opportunity for new therapeutic developments for SC-mediated nervous tissue repair. A re-interpretation of already available data in the context of new discoveries in signal transduction research is also needed, as the field continues to evolve swiftly. Remaining challenges include achieving complete elucidation of the non-canonical cAMP pathway that underlies myelination as well as a more in-depth understanding of the receptor-ligand interactions that differentially mediate the cAMP-dependent control of SC proliferation and myelination in vivo. In light of the revitalized concept that SCs myelinate (or not) as determined at least in part by cAMP, there is, in my opinion, extensive room for innovation in addressing the treatment of nerve system injuries and myelin diseases through cAMP-based therapies. This work was supported by NIH-NINDS Grants NS009923 and NS084326, The Miami Project to Cure Paralysis and The Buoniconti Fund.
Today's Internet is full of applications by which users share potentially private information with each other. Recently, the privacy concerns of users are rising and users gradually become more suspicious with respect to the use of their (personal) information. In this thesis, we aim at bringing secure multi-party computation closer to common Internet users. The main goal is to design and implement privacy-preserving reconciliation-based applications for multiple users which are secure against passive and active attackers. Additionally, our solutions should be efficient enough to be practical and usable enough even for non-technical users.As a main contribution in theory, we present different privacy-preserving multi-party reconciliation protocols based on an additively homomorphic cryptosystem that are secure against passive attackers (semi-honest model). We also propose reconciliation protocols that are secure against active attackers (malicious model) by applying zero-knowledge proof techniques. The stronger security model comes at the price of efficiency. As a prerequisite, we develop several novel cryptographic tools in the areas of privacy-preserving set operations and zero-knowledge proofs of knowledge. We also analyze to what extent fully homomorphic cryptosystems can be used for multi-party privacy-preserving reconciliation protocols. As a main contribution in practice, we introduce SMC-MuSe, a framework for Secure Multi-Party Computation on MultiSets. SMC-MuSe is a carefully designed framework for secure multi-party computation including an implementation of different cryptographic components, a support infrastructure, multi-party privacy-preserving reconciliation protocols, and two user-friendly applications for the desktop and mobile environment. We also evaluate the efficiency of the SMC-MuSe framework. In particular, we measure the computation and communication overhead of all implemented components within the SMC-MuSe framework. As a third line of work, we propose different application scenarios in the areas of event scheduling, e-voting, and electronic auctions for reconciliation protocols. We examine the practicability of one particular user-friendly application of SMC-MuSe by conducting a user study on our Android application Prefer. The user study shows that Prefer is a useful and very interesting application for today's smartphone users. Finally, we show the potential of reconciliation protocols for common Internet users by conducting a user study on privacy-preserving reconciliation in the Internet. The user study shows that our reconciliation protocols are useful in different application scenarios for common Internet users.
According to the development of the Internet of Things,the paper put forward a newkind of RFID mutual authentication protocol. This is different from the traditional based on the encryption algorithm processing authentication information authentication protocol,the newprotocol used of the authentication method of zero-knowledge proof to member certification,and make the member authentication's security is equal to its own code of identity's security. The newprotocol solves the problem about member's certified safety depends on information security of all members who participate in the traditional authentication protocol. Newprotocol can satisfy a tag's security authentication when it is applied to multiple RFID system. This paper discusses the newprotocol's detailed description and using the Strand Space Model to prove the protocol at least meet the authentication,secrecy and tag untraceability.
For the cheating problem in group signature,With the discrete logarithm problem and zero-knowledge proof protocol,and combined with the participants'identity,agroup signature scheme without trusted center is presented.In the scheme,there is no trusted key distribution center,and the dealer is also a participant,each participant's secret shadow is composed of participants through the shadow of their own secret calculation to get,the group public key recovery is invisible recovery.The analysis shows that the scheme is safe and efficient.
This paper presents Secure Comparator, a way to implement Zero Knowledge Proof algorithm called Socialist Millionaire’s Problem, to compare secrets between two parties. Compared to existing implementations, Secure Comparator provides better security guarantees, stronger cryptographic math, and, possibly, more integration-friendly architecture.
<p>This thesis develops Bayesian latent class models for nested categorical data, e.g., people nested in households. The applications focus on generating synthetic microdata for public release and imputing missing data for household surveys, such as the 2010 U.S. Decennial Census.</p><p>The first contribution is methods for evaluating disclosure risks in fully synthetic categorical data. I quantify disclosure risks by computing Bayesian posterior probabilities that intruders can learn confidential values given the released data and assumptions about their prior knowledge. I demonstrate the methodology on a subset of data from the American Community Survey (ACS). The methods can be adapted to synthesizers for nested data, as demonstrated in later chapters of the thesis.</p><p>The second contribution is a novel two-level latent class model for nested categorical data. Here, I assume that all configurations of groups and units are theoretically possible. I use a nested Dirichlet Process prior distribution for the class membership probabilities. The nested structure facilitates simultaneous modeling of variables at both group and unit levels. I illustrate the modeling by generating synthetic data and imputing missing data for a subset of data from the 2012 ACS household data. I show that the model can capture within group relationships more effectively than standard one-level latent class models.</p><p>The third contribution is a version of the nested latent class model adapted for theoretically impossible combinations, e.g. a household with two household heads or a child older than her biological father. This version assigns zero probability to those impossible groups and units. I present a proof that the Markov Chain Monte Carlo (MCMC) sampling strategy estimates the desired target distribution. I illustrate this model by generating synthetic data and imputing missing data for a subset of data from the 2011 ACS household data. The results indicate that this version can estimate the joint distribution more effectively than the previous version.</p>
Cryptography relies on Mathematics in all its aspects, beginning from the constructions relying on various mathematical theories, continuing with security evaluation of cryptographic systems, and proving their security, and finally ending in implementation.Recently, new security threats are posed by the emerging quantum computing technology.Specifically, quantum algorithms can break some public-key encryption schemes such as RSA and Elgamal, which are widely used for protection of computer systems and networks.This issue demands us to develop a new generation of cryptographic systems, which will serve as secure alternatives to the currently used ones.Such the new systems are referred to as the post-quantum cryptography.One promising direction in post-quantum cryptography is the systems whose security is based on hardness of mathematical problems arising in the context of coding theory.In particular, the problem of decoding random linear codes has been studied for over 30 years, and still no polynomial-time solution has been proposed, even when using quantum algorithms.In this thesis, we focus on this area, which is called the code-based cryptography.The first code-based public-key encryption (PKE) scheme was introduced by R.J. McEliece in 1978.Since then, various code-based public-key encryption, digital signature and identification schemes were introduced, but currently, one of the main challenges is to introduce more advanced cryptographic functionalities based on coding.In this thesis, first, we give a brief introduction about post-quantum cryptography and codebased cryptography, and then we provide the background information about the cryptographic primitives, which we will study, as well as the relevant notions and results from coding theory and cryptography.Next, we introduce our contributions as follows.Firstly, we study zero-knowledge (ZK) identification schemes based q-ary linear codes.We show that when q < 5, a straightforward generalization of Stern's ZK identification scheme (1993) is more efficient in terms of both communication and computation, as compared to the ZK identification scheme by Cayrel, Vron and El Yousfi Alaoui (2010), which is specifically designed for q-ary codes.Secondly, we introduce the first proof of plaintext knowledge (PPK) for the McEliece PKE and the Niederreiter PKE.These protocols allow the encryptor to prove the knowledge of the plaintext contained in a given ciphertext to any party, who does not hold the secret key for decryption.We also provide a performance evaluation for the proposed schemes.
We give a new proof of the existence of public-coin concurrent zero-knowledge arguments for NP in the plain model under standard assumptions (the existence of one-to-one one-way func-tions and collision-resistant hash functions), which was originally proven by Goyal (STOC’13). In the proof, we use a new variant of the non-black-box simulation technique of Barak (FOCS’01). An important property of our simulation technique is that the simulator runs in a straight-line manner in the fully concurrent setting. Compared with the simulation technique of Goyal, which also has such a property, the analysis of our simulation technique is (arguably) simpler. This article is a minor revision of the version that appears in the proceedings of TCC 2015. 1
In this thesis we present our contribution in the field of post-quantum cryptography. We introduce a new notion of weakly Random-Self-Reducible public-key cryptosystem and show how it can be used to implement secure Oblivious Transfer. We also show that two recent (Post-quantum) cryptosystems can be considered as weakly Random-Self-Reducible. We introduce a new problem called Isometric Lattice Problem and reduce graph isomorphism and linear code equivalence to this problem. We also show that this problem has a perfect zero-knowledge interactive proof with respect to a malicious verifier; this is the only hard problem in lattices that is known to have this property.
Rafail Ostrovsky, Giuseppe Persiano, Ivan Visconti
In this work, we show how to use the positive results on succinct argument systems to prove impossibility results on leakage-resilient black-box zero knowledge. This recently proposed notion of zero knowledge deals with an adversary that can make leakage queries on the state of the prover. Our result holds for black-box simulation only and we also give some insights on the non-black-box case. Additionally, we show that, for several functionalities, leakage-resilient multi-party computation is impossible (regardless of the number of players and even if just one player is corrupted). More in details, we achieve the above results by extending a technique of [Nielsen, Venturi, Zottarel – PKC 13] to prove lower bounds for leakage-resilient security. Indeed, we use leakage queries to run an execution of a communication-efficient protocol in the head of the adversary. Moreover, to defeat the black-box simulator we connect the above technique for leakage resilience to security against reset attacks. Our results show that the open problem of [Ananth, Goyal, Pandey – Crypto 14] (i.e., continual leakage-resilient proofs without a common reference string) has a negative answer when security through black-box simulation is desired. Moreover our results close the open problem of [Boyle et al. – STOC 12] for the case of black-box simulation (i.e., the possibility of continual leakage-resilient secure computation without a leak-free interactive preprocessing).
Project development in a power enterprise always needs to authorize external devices access to the enterprise intranet for testing. In order to avoid an external device with a virus and pose a security risk to the power information system, external devices should have strict security assessment before access the enterprise intranet. But after the security assessment, the device user still be possible to change the platform configuration. Remote attestation is one of important measures when two sides need to communicate. It is concernful to attest the remote platform is trusty but not revealing the any private information of the platform. For this reason, we designed a novel remote anonymous attestation protocol based on TCM. The proposed protocol does not need extra zero knowledge proof and the involvement of the third trusted party and the composite signature scheme is proved secure against existential forgery on adaptively chosen message. So this protocol has better security and execution property.
As for the security of digital signature,this paper takes advantage of the discrete logarithm problem and zeroknowledge proof protocol,combines with( t,n) threshold signature scheme and the identity of the participants,and presents a digital signature scheme based on secret sharing. In the scheme,there is no trusted key distribution center,and the secret share of the participants is generated by the participants themselves and can be used repeatedly,furthermore,the identity of the participants is generated by their own secret share. Only the public information can be updated,which will not affect the participants' secret share. Anyone can detect whether the dealer is cheating the participants or whether there is cheating between participants. Only the authorized subset client can represent group to sign; the generation and verification of the partial signature and group signature are effective. The discrete logarithm problem and zero-knowledge proof protocol guarantees the security of information transmission,which further improves the security of the scheme. The analysis indicates that the scheme is safe and efficient.
Can an exchange be “dark,” so that orders are not displayed, while simultaneously trustworthy, so that the execution of trades and flow of information occur as promised? SEC actions against dark pools suggest cause for concern, and regulators seem to be moving towards requiring more disclosure. Yet there is a clear tension: trading order information is widely exploited. Therefore, institutional investors have a strong interest in keeping pre-trade information about large trades hidden. Secrecy-preserving proofs of correctness can be used to build trust without revealing unnecessary information. By performing operations on obfuscated representations of orders (perhaps encrypted or otherwise hidden), a zero knowledge proof can be provided, allowing anyone to verify correctness of trades. Crucially, this can be done without revealing any information beyond this correctness. This technology can be usefully applied to construct provably trustworthy dark pools. Additional practical protocols relax the definition of “zero knowledge" to reveal limited information, providing necessary transparency for efficient market operation while limiting information that can be exploited by observers. Coupled with Trusted Computing hardware, these protocols can provide an excellent balance of practicality with secrecy
Randomized encodings of functions can be used to replace a “complex” function $f(x)$ by a “simpler” randomized mapping $\hat{f}(x;r)$ whose output distribution on an input $x$ encodes the value of $f(x)$ and hides any other information about $x$. One desirable feature of randomized encodings is low online complexity. That is, the goal is to obtain a randomized encoding $\hat{f}$ of $f$ in which most of the output can be precomputed and published before seeing the input $x$. When the input $x$ is available, it remains to publish only a short string $\hat{x}$, where the online complexity of computing $\hat{x}$ is independent of (and is typically much smaller than) the complexity of computing $f$. Yao's garbled circuit construction gives rise to such randomized encodings in which the online part $\hat{x}$ consists of $n$ encryption keys of length $\kappa$ each, where $n=|x|$ and $\kappa$ is a security parameter. Thus, the online rate $|\hat{x}|/|x|$ of this encoding is proportional to the security parameter $\kappa$. In this paper, we show that the online rate can be dramatically improved. Specifically, we show how to encode any polynomial-time computable function $f:\{0,1\}^n\to\{0,1\}^{m(n)}$ with online rate of $1+o(1)$ and with nearly linear online computation. More concretely, the online part $\hat{x}$ consists of an $n$-bit string and a single encryption key. These constructions can be based on the decisional Diffie--Hellman (DDH) assumption, the learning with errors (LWE) assumption, or the RSA assumption. We also present a variant of this result which applies to arithmetic formulas, where the encoding only makes use of arithmetic operations, as well as several negative results which complement our positive results. Our positive results can lead to efficiency improvements in most contexts where randomized encodings of functions are used. We demonstrate this by presenting several concrete applications. These include protocols for secure multiparty computation and for noninteractive verifiable computation in the preprocessing model which achieve, for the first time, an optimal online communication complexity, as well as noninteractive zero-knowledge proofs which simultaneously minimize the online communication and the prover's online computation.
Abstract. Functional encryption (FE) enables sophisticated control over decryption rights in a multi-user scenario, while functional signature (FS) allows to enforce complex constraints on sign-ing capabilities. This paper introduces the concept of functional signcryption (FSC) that aims to provide the functionalities of both FE and FS in an unified cost-effective primitive. FSC provides a solution to the problem of achieving confidentiality and authenticity simultaneously in digital communication and storage systems involving multiple users with better efficiency compared to a sequential implementation of FE and FS. We begin by providing formal definition of FSC and formu-lating its security requirements. Next, we present a generic construction of this challenging primitive that supports arbitrary polynomial-size signing and decryption functions from known cryptographic building blocks, namely, indistinguishability obfuscation (IO) and statistically simulation-sound non-interactive zero-knowledge proof of knowledge (SSS-NIZKPoK). Finally, we exhibit a number of rep-resentative applications of FSC: (I) We develop the first construction of attribute-based signcryption (ABSC) supporting signing and decryption policies representable by general polynomial-size circuits from FSC. (II) We show how FSC can serve as a tool for building SSS-NIZKPoK system and IO, a result which in conjunction with our generic FSC construction can also be interpreted as establishing an equivalence between FSC and the other two fundamental cryptographic primitives.
Abstract. In a secure physical computation, a set of parties each have physical inputs and jointly compute a function of their inputs in a way that reveals no information to any party except for the output of the function. Recent work in CRYPTO’14 presented examples of physical zero-knowledge proofs of physical properties, a special case of secure physical two-party computation in which one party has a physical input and the second party verifies a boolean function of that input. While the work suggested a general framework for modeling and analyzing physi-cal zero-knowledge protocols, it did not provide a general theory of how to prove any physical property with zero-knowledge. This paper takes an orthogonal approach using disposable circuits (DC)—cheap hardware tokens that can be completely destroyed after a computation—an ex-tension of the familiar tamper-proof token model. In the DC model, we demonstrate that two parties can compute any function of their physical inputs in a way that leaks at most 1 bit of additional information to either party. Moreover, our result generalizes to any multi-party physical computation. Formally, our protocols achieve unconditional UC-security with input-dependent abort. 1