Deep Random based Key Exchange protocol resisting unlimited MITM

We present a protocol enabling two legitimate partners sharing an initial secret to mutually authenticate and to exchange an encryption session key. The opponent is an active Man In The Middle (MITM) with unlimited computation and storage capacities. The resistance to unlimited MITM is obtained through the combined use of Deep Random secrecy, formerly introduced and proved as unconditionally secure against passive opponent for key exchange, and universal hashing techniques. We prove the resistance to MITM interception attacks, and show that (i) upon successful completion, the protocol leaks no residual information about the current value of the shared secret to the opponent, and (ii) that any unsuccessful completion is detectable by the legitimate partners. We also discuss implementation techniques.Comment: 14 pages. V2: Updated reminder in the formalism of Deep Random assumption. arXiv admin note: text overlap with arXiv:1611.01683, arXiv:1507.0825

Equivalent efficiency of a simulated photon-number detector

Homodyne detection is considered as a way to improve the efficiency of communication near the single-photon level. The current lack of commercially available {\it infrared} photon-number detectors significantly reduces the mutual information accessible in such a communication channel. We consider simulating direct detection via homodyne detection. We find that our particular simulated direct detection strategy could provide limited improvement in the classical information transfer. However, we argue that homodyne detectors (and a polynomial number of linear optical elements) cannot simulate photocounters arbitrarily well, since otherwise the exponential gap between quantum and classical computers would vanish.Comment: 4 pages, 4 figure

Coherence of marine alien species biosecurity legislation: A study of England and Wales

The marine environment is particularly at risk from the intentional and unintentional introduction and spread of invasive alien species (IAS); preventing their introduction and spread from occurring is therefore, a key component in the on-going management of marine IAS. Ensuring legislation is coherent and consistent is essential to the success of managing the existing and future impacts of marine IAS. We explore the coherence (determined as consistency and interaction) of marine biosecurity legislation for IAS at different geopolitical scales. There was consistency between both the Bern Convention and Convention on Biological Diversity and European and national legislation that had been created in response. There was a lack of interaction evidenced by the Ballast Water Management Convention, which had not yet been transposed into regional (mainly European) or national legislation. Implementation measures such as legislation should be coherent as any failure in the chain could potentially weaken the overall effort to establish and maintain biosecurity and achieve behaviour change

Exploring the attitudes to and uptake of biosecurity practices for invasive non-native species: views amongst stakeholder organisations working in UK natural environments

Invasions by invasive non-native species (INNS) can have profound consequences for natural environments, impacting on biodiversity and the biophysical landscape in ways that can endanger other species, human wellbeing and infrastructure. The financial costs of dealing with established INNS populations can be extremely high. Biosecurity measures (simple procedures designed to reduce the risk of human activities spreading INNS to new areas) are being promoted in order to minimize these negative impacts and associated costs. This paper reports on research undertaken with stakeholder organisations that operate within UK natural environments. It aims to evaluate stakeholder perceptions of their role in INNS biosecurity practice in the UK, and the implications of this for INNS strategy more broadly. Semi-structured interviews were undertaken with organisation representatives to explore current practices and communications about INNS and perceptions of barriers and opportunities to implement better biosecurity. Whilst participants generally agreed on the need for biosecurity, there were variations among participants in levels of knowledge about INNS (related to background) and the capacity of organisations to engage in biosecurity practices (related to organisational size). Critical barriers to biosecurity were identified as costs, lack of clear guidance, difficulties changing attitudes and implementing collective responsibility, and reactionary versus precautionary approaches. As a result, partnership working on INNS is difficult and action tends to focus on individual species perceived as the most threatening to a particular organisations’ interests. In this way, action on INNS biosecurity faces the kinds of barriers that are common to many environmental problems where individuals/organisations prioritise self-interest despite the potential to obtain greater benefits if collective action could be achieved

Quantum key distribution using gaussian-modulated coherent states

Quantum continuous variables are being explored as an alternative means to implement quantum key distribution, which is usually based on single photon counting. The former approach is potentially advantageous because it should enable higher key distribution rates. Here we propose and experimentally demonstrate a quantum key distribution protocol based on the transmission of gaussian-modulated coherent states (consisting of laser pulses containing a few hundred photons) and shot-noise-limited homodyne detection; squeezed or entangled beams are not required. Complete secret key extraction is achieved using a reverse reconciliation technique followed by privacy amplification. The reverse reconciliation technique is in principle secure for any value of the line transmission, against gaussian individual attacks based on entanglement and quantum memories. Our table-top experiment yields a net key transmission rate of about 1.7 megabits per second for a loss-free line, and 75 kilobits per second for a line with losses of 3.1 dB. We anticipate that the scheme should remain effective for lines with higher losses, particularly because the present limitations are essentially technical, so that significant margin for improvement is available on both the hardware and software.Comment: 8 pages, 4 figure

Quantum Noise Randomized Ciphers

We review the notion of a classical random cipher and its advantages. We sharpen the usual description of random ciphers to a particular mathematical characterization suggested by the salient feature responsible for their increased security. We describe a concrete system known as AlphaEta and show that it is equivalent to a random cipher in which the required randomization is effected by coherent-state quantum noise. We describe the currently known security features of AlphaEta and similar systems, including lower bounds on the unicity distances against ciphertext-only and known-plaintext attacks. We show how AlphaEta used in conjunction with any standard stream cipher such as AES (Advanced Encryption Standard) provides an additional, qualitatively different layer of security from physical encryption against known-plaintext attacks on the key. We refute some claims in the literature that AlphaEta is equivalent to a non-random stream cipher.Comment: Accepted for publication in Phys. Rev. A; Discussion augmented and re-organized; Section 5 contains a detailed response to 'T. Nishioka, T. Hasegawa, H. Ishizuka, K. Imafuku, H. Imai: Phys. Lett. A 327 (2004) 28-32 /quant-ph/0310168' & 'T. Nishioka, T. Hasegawa, H. Ishizuka, K. Imafuku, H. Imai: Phys. Lett. A 346 (2005) 7

Restoration of the rabbit corneal surface after total epithelial debridement and complete limbal excision

How is the corneal epithelium restored when all of it plus the limbus have been eliminated? This investigation explored the possibility that this may be achieved through the conjunctival epithelium. The corneal epithelium of the right eye of 12 rabbits (Oryctolagus cuniculus) was totally scraped followed by surgical excision of the limbus plus 1.0-1.5 mm of the adjacent conjunctiva. Antibiotics and corticosteroids were applied for 1 week after surgery. Histological and immunohistochemical techniques were used to monitor the events taking place on the eye surface 2 weeks and 1, 3 and 6 months thereafter. Initially, the corneal surface was covered by conjunctival-like epithelium. After 1 month and more prominently at 3 and 6 months an epithelium displaying the morphological features of the cornea and reacting with the AE5 antibody was covering the central region. It is likely that the corneal epithelium originated from undifferentiated cells of the conjunctiva interacting with the corneal stroma.CNPqCNPqFAPESPFAPESPFAEPA-HC-FMRPFAEPAHCFMR

Quantum information can be negative

Given an unknown quantum state distributed over two systems, we determine how much quantum communication is needed to transfer the full state to one system. This communication measures the "partial information" one system needs conditioned on it's prior information. It turns out to be given by an extremely simple formula, the conditional entropy. In the classical case, partial information must always be positive, but we find that in the quantum world this physical quantity can be negative. If the partial information is positive, its sender needs to communicate this number of quantum bits to the receiver; if it is negative, the sender and receiver instead gain the corresponding potential for future quantum communication. We introduce a primitive "quantum state merging" which optimally transfers partial information. We show how it enables a systematic understanding of quantum network theory, and discuss several important applications including distributed compression, multiple access channels and multipartite assisted entanglement distillation (localizable entanglement). Negative channel capacities also receive a natural interpretation

Multiscale Modeling of a Nanoelectromechanical Shuttle

In this article, we report a theoretical analysis of a nanoelectromechanical shuttle based on a multiscale model that combines microscopic electronic structure data with macroscopic dynamics. The microscopic part utilizes a (static) density functional description to obtain the energy levels and orbitals of the shuttling particle together with the forces acting on the particle. The macroscopic part combines stochastic charge dynamics that incorporates the microscopically evaluated tunneling rates with a Newtonian dynamics. We have applied the multiscale model to describe the shuttling of a single copper atom between two gold-like jellium electrodes. We find that energy spectrum and particle surface interaction greatly influence shuttling dynamics; in the specific example that we studied the shuttling is found to involve only charge states Q=0 and Q=+e. The system is found to exhibit two quasi-stable shuttling modes, a fundamental one and an excited one with a larger amplitude of mechanical motion, with random transitions between them.Comment: 9 pages, 9 figure

Quantum authentication with key recycling

We show that a family of quantum authentication protocols introduced in [Barnum et al., FOCS 2002] can be used to construct a secure quantum channel and additionally recycle all of the secret key if the message is successfully authenticated, and recycle part of the key if tampering is detected. We give a full security proof that constructs the secure channel given only insecure noisy channels and a shared secret key. We also prove that the number of recycled key bits is optimal for this family of protocols, i.e., there exists an adversarial strategy to obtain all non-recycled bits. Previous works recycled less key and only gave partial security proofs, since they did not consider all possible distinguishers (environments) that may be used to distinguish the real setting from the ideal secure quantum channel and secret key resource.Comment: 38+17 pages, 13 figures. v2: constructed ideal secure channel and secret key resource have been slightly redefined; also added a proof in the appendix for quantum authentication without key recycling that has better parameters and only requires weak purity testing code