Can you sign a quantum state?

Cryptography with quantum states exhibits a number of surprising and counterintuitive features. In a 2002 work, Barnum et al. argue that these features imply that digital signatures for quantum states are impossible (Barnum et al., FOCS 2002). In this work, we ask: can all forms of signing quantum data, even in a possibly weak sense, be completely ruled out? We give two results which shed significant light on this basic question.First, we prove an impossibility result for digital signatures for quantum data, which extends the result of Barnum et al. Specifically, we show that no nontrivial combination of correctness and security requirements can be fulfilled, beyond what is achievable simply by measuring the quantum message and then signing the outcome. In other words, only classical signature schemes exist.We then show a positive result: a quantum state can be signed with the same security guarantees as classically, provided that it is also encrypted with the public key of the intended recipient. Following classical nomenclature, we call this notion quantum signcryption. Classically, signcryption is only interesting if it provides superior performance to encypt-then-sign. Quantumly, it is far more interesting: it is the only signing method available. We develop "as-strong-as-classical" security definitions for quantum signcryption and give secure constructions based on post-quantum public-key primitives. Along the way, we show that a natural hybrid method of combining classical and quantum schemes can be used to "upgrade" a secure classical scheme to the fully-quantum setting, in a wide range of cryptographic settings including signcryption, authenticated encryption, and CCA security.

HARDWARE SUPPORT PROCEDURES FOR ASYMMETRIC AUTHENTICATION OF THE INTERNET OF THINGS

Subject of research: procedures of asymmetric authentication of Internet of Things nodes to ensure the highest level of security using cryptographic chips. The aim of the article is to study the ways of potential use of cryptographic chips to ensure secure authentication of Internet of Things sites using asymmetric cryptography procedures. The article solves the following tasks: analysis of hardware support technologies for asymmetric cryptography of the Internet of Things; definition of secure procedures for asymmetric authentication of Internet of Things sites and their constituent elements: creation of certificates, verification of public and private keys. Research methods: method of structural and functional analysis and design of complex systems, methods of identification and authentication of information objects, cryptographic methods of information protection, methods of security analysis of distributed information systems. The novelty of the study is the analysis of hardware support technologies for asymmetric cryptography of Internet of Things with cryptographic chips and the definition of structural and functional schemes for the implementation of procedures for asymmetric authentication of Internet of Things. Distinctive features of the provided asymmetric authentication schemes and procedures are: ensuring an increased level of information security through secure storage of cryptographic keys, digital signatures, certificates, confidential data in a novelty security environment protected from external attacks and no need to store private keys on the host side. The results of the work are procedures and schemes of application of cryptomicrops of asymmetric authentication to ensure the protection of Internet of Things. Analysis of the functioning of the presented schemes allowed to draw the following conclusions. The proposed structural and functional schemes for the implementation of procedures for asymmetric authentication of Internet of Things using cryptographic chips give the user an easy opportunity to implement cryptography without expertise in this field. These chips use the ECDSA digital signature computing and verification hardware with elliptical curve advantages, as a proven and reliable authentication algorithm, and the ECDH symmetric encryption session key generation unit. The provided schemes and procedures support three components of information security, namely: confidentiality, integrity and authenticity of data. Examples of potential applications of the provided schemes and procedures can be implemented using any asymmetric authentication chip, but it is recommended that they be used to generate encryption session keys and where digital signatures are required to verify data and code for integrity and authenticity.

Using I2P Encrypted Virtual Tunnels for a Secure and Anonymous Communication in VANets: I2P Vehicular Protocol (IVP)

Providing security and anonymity within VANet requires application of robust and secure models that meet several characteristics of VANet. I2P as a secure protocol designed to anonymize the communication on the internet, can be used as a reference model to develop new mechanisms of security and anonymity in VANet. I2P uses robust mechanisms and strong algorithms to reinforce the security and the anonymity of the communication. However, the difference between internet and VANet in terms of mobility and connectivity of nodes presents a big issue that needs to be treated when using I2P mechanisms in VANet. In the previous work [1], we propose a protocol based on tunnels and encryption algorithms that use digital signatures and authentication mechanisms. Tunnels are created in static scenarios and without maintaining their existence. In this paper, we complete the last version of the proposed protocol (I2P Vehicular Protocol) by integrating a tunnel maintenance algorithm for maintaining the existence of the created tunnels during the communication. This algorithm allows the implementation of the protocol in mobile scenarios of VANet. The effectiveness and security of IVP protocol are proved by analyzing the added part related to the tunnel maintenance process and showing performance results (end-to-end delay, PDR and overhead). Simulation scenarios were executed using NS3 simulator.

P2P PROTOCOL FOR TRANSFERRING DIGITAL INHERITANCE

This document proposes a new protocol for sharing sensitive digital data in the form of digital inheritance. Main goals of the protocol are ensuring the integrity and confidentiality of the data as well as the anonymity of the receiver. The protocol makes use of different cryptographic algorithms in order to ensure certain features of transmitted data, including digital signatures, MAC codes and stealth addresses.

Image Forensic Tool (IFT)

Images now-a-days are often used as an authenticated proof for any cyber-crime. Images that do not remain genuine can mislead the court of law. The fast and dynamically growing technology doubts the trust in the integrity of images. Tampering mostly refers to adding or removing important features from an image without leaving any obvious trace. In earlier days, digital signatures were used to preserve the integrity, but now a days various tools are available to tamper digital signatures as well. Even in various state-of-the-art works in tamper detection, there are various restrictions in the type of inputs and the type of tampering detection. In this paper, the researchers propose a prototype model in the form of a tool that will retrieve all the image files from given digital evidence and detect tampering in the images. For various types of tampering, different tampering detection algorithms have been used. The proposed prototype will detect if tampering has been done or not and will classify the image files into groups based on the type of tampering.

Shuffling Public Keys (A Peer-to-peer Voting Algorithm)

A peer-to-peer, permissionless, and distributed cryptographic voting system that relies only on the existence of generic digital signatures and encryption.

Quantum digital signatures with smaller public keys

We introduce a variant of quantum signatures in which nonbinary symbols are signed instead of bits. The public keys are fingerprinting states, just as in the scheme of Gottesman and Chuang \cite{GC2001}, but we allow for multiple ways to reveal the private key partially. The effect of this modification is a reduction of the number of qubits expended per message bit. Asymptotically the expenditure becomes as low as one qubit per message bit. We give a security proof, and we present numerical results that show how the improvement in public key size depends on the message length.