arXiv subjects

Alex Shafarenko

Publications and source records attributed to Alex Shafarenko.

11 recordsLinked to original sources

arXiv2024

Non-Degenerate One-Time Pad and the integrity of perfectly secret messages

We present a new construction of a One Time Pad (OTP) with inherent diffusive properties and a redundancy injection mechanism that benefits from them. The construction is based on interpreting the plaintext and key as members of a permutation group in the Lehmer code representation after conversion to factoradic. The so constructed OTP translates any perturbation of the ciphertext to an unpredictable, metrically large random perturbation of the plaintext. This allows us to provide unconditional integrity assurance without extra key material. The redundancy is injected using Foata's "pun": the reading of the one-line representation as the cyclic one; we call this Pseudo Foata Injection. We obtain algorithms of quadratic complexity that implement both mechanisms.

cs.CR↗

arXiv2022

Winternitz stack protocols

This paper proposes and evaluates a new bipartite post-quantum digital signature protocol based on Winternitz chains and the HORS oracle. Mutually mistrustful Alice and Bob are able to agree and sign a series of documents in a way that makes it impossible (within the assumed security model) to repudiate their signatures. The number of signatures supported by a single public key is limited by a large number but the security of the signature scheme is not diminished by repeated application. A single public key supports both parties. Some ramifications are discussed, security parameters evaluated and an application area delineated for the proposed concept.

cs.CR↗

arXiv2021

Indexing structures for the PLS blockchain

This paper studies known indexing structures from a new point of view: minimisation of data exchange between an IoT device acting as a blockchain client and the blockchain server running a protocol suite that includes two Guy Fawkes protocols, PLS and SLVP. The PLS blockchain is not a cryptocurrency instrument; it is an immutable ledger offering guaranteed non-repudiation to low-power clients without use of public key crypto. The novelty of the situation is in the fact that every PLS client has to obtain a proof of absence in all blocks of the chain to which its counterparty does not contribute, and we show that it is possible without traversing the block's Merkle tree. We obtain weight statistics of a leaf path on a sparse Merkle tree theoretically, as our ground case. Using the theory we quantify the communication cost of a client interacting with the blockchain. We show that large savings can be achieved by providing a bitmap index of the tree compressed using Tunstall's method. We further show that even in the case of correlated access, as in two IoT devices posting messages for each other in consecutive blocks, it is possible to prevent compression degradation by re-randomising the IDs using a pseudorandom bijective function. We propose a low-cost function of this kind and evaluate its quality by simulation, using the avalanche criterion.

cs.CR↗

arXiv2020

A PLS blockchain for IoT applications: protocols and architecture

This paper proposes an architecture and a protocol suite for a permissioned blockchain for a local IoT network. The architecture is based on a sealed Sequencer and a Fog Server running (post-quantum) Guy Fawkes protocols. The blocks of the blockchain are stored in networked Content Addressable Storage alongside any user data and validity proofs. We maintain that a typical IoT device can, despite its resource limitations, use our blockchain protocols directly, without a trusted intermediary. This includes posting and monitoring transactions as well as off-chain (post-quantum) emergency communications without an explicit public key. Keywords: blockchain, Guy Fawkes protocol, post-quantum, HORS-OTS, LoRa, concurrent transmission

cs.CR↗

arXiv2016

Configuring Cloud-Service Interfaces Using Flow Inheritance

Technologies for composition of loosely-coupled web services in a modular and flexible way are in high demand today. On the one hand, the services must be flexible enough to be reused in a variety of contexts. On the other hand, they must be specific enough so that their composition may be provably consistent. The existing technologies (WS-CDL, WSCI and session types) require a behavioural contract associated with each service, which is impossible to derive automatically. Furthermore, neither technology supports flow inheritance: a mechanism that automatically and transparently propagates data through service pipelines. This paper presents a novel mechanism for automatic interface configuration of such services. Instead of checking consistency of the behavioural contracts, our approach focuses solely on that of data formats in the presence of subtyping, polymorphism and flow inheritance. The paper presents a toolchain that automatically derives service interfaces from the code and performs interface configuration taking non-local constraints into account. Although the configuration mechanism is global, the services are compiled separately. As a result, the mechanism does not raise source security issues despite global service availability in adaptable form.

cs.SE↗

arXiv2016

A Constraint Satisfaction Method for Configuring Non-Local Service Interfaces

Modularity and decontextualisation are core principles of a service-oriented architecture. However, the principles are often lost when it comes to an implementation of services, as a result of a rigidly defined service interface. The interface, which defines a data format, is typically specific to a particular context and its change entails significant redevelopment costs. This paper focuses on a two-fold problem. On the one hand, the interface description language must be flexible enough for maintaining service compatibility in a variety of different contexts without modification of the service itself. On the other hand, the composition of interfaces in a distributed environment must be provably consistent. The existing approaches for checking compatibility of service choreographies are either inflexible (WS-CDL and WSCI) or require behaviour specification associated with each service, which is often impossible to provide in practice. We present a novel approach for automatic interface configuration in distributed stream-connected components operating as closed-source services (i.e. the behavioural protocol is unknown). We introduce a Message Definition Language (MDL), which can extend the existing interfaces description languages, such as WSDL, with support of subtyping, inheritance and polymorphism. The MDL supports configuration variables that link input and output interfaces of a service and propagate requirements over an application graph. We present an algorithm that solves the interface reconciliation problem using constraint satisfaction that relies on Boolean satisfiability as a subproblem.

cs.LO↗

arXiv2015

Interface Reconciliation in Kahn Process Networks using CSP and SAT

We present a new CSP- and SAT-based approach for coordinating interfaces of distributed stream-connected components provided as closed-source services. The Kahn Process Network (KPN) is taken as a formal model of computation and a Message Definition Language (MDL) is introduced to describe the format of messages communicated between the processes. MDL links input and output interfaces of a node to support flow inheritance and contextualisation. Since interfaces can also be linked by the existence of a data channel between them, the match is generally not only partial but also substantially nonlocal. The KPN communication graph thus becomes a graph of interlocked constraints to be satisfied by specific instances of the variables. We present an algorithm that solves the CSP by iterative approximation while generating an adjunct Boolean SAT problem on the way. We developed a solver in OCaml as well as tools that analyse the source code of KPN vertices to derive MDL terms and automatically modify the code by propagating type definitions back to the vertices after the CSP has been solved. Techniques and approaches are illustrated on a KPN implementing an image processing algorithm as a running example.

cs.PL↗

arXiv2014

AstraKahn: A Coordination Language for Streaming Networks

This is a preliminary version of the language report. It contains key definitions, specifications and some examples, but lacks completeness. The full document will include Chapter 3 (Data and Instrumentation Layer) and will comprise an appendix giving the complete syntax and some whole program examples. The purpose of the present document is to fix the concepts and major features of the language and to enable the production of the definition document that is required for implementation.

cs.PL↗

arXiv2014

A Case Study in Coordination Programming: Performance Evaluation of S-Net vs Intel's Concurrent Collections

We present a programming methodology and runtime performance case study comparing the declarative data flow coordination language S-Net with Intel's Concurrent Collections (CnC). As a coordination language S-Net achieves a near-complete separation of concerns between sequential software components implemented in a separate algorithmic language and their parallel orchestration in an asynchronous data flow streaming network. We investigate the merits of S-Net and CnC with the help of a relevant and non-trivial linear algebra problem: tiled Cholesky decomposition. We describe two alternative S-Net implementations of tiled Cholesky factorization and compare them with two CnC implementations, one with explicit performance tuning and one without, that have previously been used to illustrate Intel CnC. Our experiments on a 48-core machine demonstrate that S-Net manages to outperform CnC on this problem.

cs.PL↗

arXiv2013

S+Net: extending functional coordination with extra-functional semantics

This technical report introduces S+Net, a compositional coordination language for streaming networks with extra-functional semantics. Compositionality simplifies the specification of complex parallel and distributed applications; extra-functional semantics allow the application designer to reason about and control resource usage, performance and fault handling. The key feature of S+Net is that functional and extra-functional semantics are defined orthogonally from each other. S+Net can be seen as a simultaneous simplification and extension of the existing coordination language S-Net, that gives control of extra-functional behavior to the S-Net programmer. S+Net can also be seen as a transitional research step between S-Net and AstraKahn, another coordination language currently being designed at the University of Hertfordshire. In contrast with AstraKahn which constitutes a re-design from the ground up, S+Net preserves the basic operational semantics of S-Net and thus provides an incremental introduction of extra-functional control in an existing language.

cs.PL↗

arXiv2011

CAL: A Language for Aggregating Functional and Extrafunctional Constraints in Streaming Networks

In this article we present the {\em Constraint Aggregation Language} (CAL), a declarative language for describing properties of stateless program components that interact by exchanging messages. CAL allows one to describe functional as well as extra-functional behaviours, such as computation latency. The CAL language intention is to be able to describe the behaviour of so-called boxes in the context of S-Net. However, the language would find application in other coordination models based on stateless components.

cs.PL↗