Towards Practical Security of Pseudonymous Signature on the BSI eIDAS Token

In this paper we present an extension of Pseudonymous Signature introduced by the German Federal BSI authority as a part of technical recommendations for electronic identity documents. Without switching to pairing friendly groups we enhance the scheme so that: (a) the issuer does not know the private keys of the citizen (so it cannot impersonate the citizen), (b) a powerful adversary that breaks any number of ID cards created by the Issuer cannot forge new cards that could be proven as fake ones, (c) deanonymization of the pseudonyms used by a citizen is a multi-party protocol, where the consent of each authority is necessary to reveal the identity of a user. (d) we propose extended features concerning fully anonymous signatures and a pragmatic revocation approach. (e) we present an argument for unlinkability (cross-domain anonymity) of the presented schemes. In this way we make a step forwards to overcome the substantial weaknesses of the Pseudonymous Signature scheme. Moreover, the extension is on top of the original scheme with relatively small number of changes, following the strategy of reusing the previous schemes -- thereby reducing the costs of potential technology update

Zero-Knowledge Proof-of-Identity: Sybil-Resistant, Anonymous Authentication on Permissionless Blockchains and Incentive Compatible, Strictly Dominant Cryptocurrencies

Zero-Knowledge Proof-of-Identity from trusted public certificates (e.g., national identity cards and/or ePassports; eSIM) is introduced here to permissionless blockchains in order to remove the inefficiencies of Sybil-resistant mechanisms such as Proof-of-Work (i.e., high energy and environmental costs) and Proof-of-Stake (i.e., capital hoarding and lower transaction volume). The proposed solution effectively limits the number of mining nodes a single individual would be able to run while keeping membership open to everyone, circumventing the impossibility of full decentralization and the blockchain scalability trilemma when instantiated on a blockchain with a consensus protocol based on the cryptographic random selection of nodes. Resistance to collusion is also considered. Solving one of the most pressing problems in blockchains, a zk-PoI cryptocurrency is proved to have the following advantageous properties: - an incentive-compatible protocol for the issuing of cryptocurrency rewards based on a unique Nash equilibrium - strict domination of mining over all other PoW/PoS cryptocurrencies, thus the zk-PoI cryptocurrency becoming the preferred choice by miners is proved to be a Nash equilibrium and the Evolutionarily Stable Strategy - PoW/PoS cryptocurrencies are condemned to pay the Price of Crypto-Anarchy, redeemed by the optimal efficiency of zk-PoI as it implements the social optimum - the circulation of a zk-PoI cryptocurrency Pareto dominates other PoW/PoS cryptocurrencies - the network effects arising from the social networks inherent to national identity cards and ePassports dominate PoW/PoS cryptocurrencies - the lower costs of its infrastructure imply the existence of a unique equilibrium where it dominates other forms of paymentComment: 2.1: Proof-of-Personhood Considered Harmful (and Illegal); 4.1.5: Absence of Active Authentication; 4.2.6: Absence of Active Authentication; 4.2.7: Removing Single-Points of Failure; 4.3.2: Combining with Non-Zero-Knowledge Authentication; 4.4: Circumventing the Impossibility of Full Decentralizatio

Practical backward unlinkable revocation in FIDO, German e-ID, Idemix and U-Prove

FIDO, German e-ID, Idemix and U-Prove constitute privacy-enhanced public-key infrastructures allowing users to authenticate in an anonymous way. This however hampers timely revocation in a privacy friendly way. From a legal perspective, revocation typically should be effective within 24 hours after user reporting. It should also be backward unlinkable, i.e. user anonymity cannot be removed after revocation. We describe a new, generic revocation mechanism based on pairing based encryption and apply it to supplement the systems mentioned. This allows for both flexible and privacy friendly revocation. Protocol execution takes less than a quarter of a second on modern smartcards. An additional property is that usage after revocation is linkable, allowing users to identify fraudulent usage after revocation. Our technique is the first Verifier Local Revocation scheme with backwards unlinkable revocation for the systems mentioned. This also allows for a setup resembling the well-known Online Certificate Status Protocol (OCSP). Here the service provider sends a pseudonym to a revocation provider that returns its status. As the information required for this is not secret the status service can be distributed over many cloud services. In addition to the status service our technique also supports the publication of a central revocation list

Blockchain: Developing Regulatory Approaches for the use of Technology in Legal Services

This paper charts the evolution of blockchain and other distributed ledger technologies as tools for radically simplifying common legal tasks such as identity verification and contract fulfilment

Anamorphic Signatures: Secrecy From a Dictator Who Only Permits Authentication!

The goal of this research is to raise technical doubts regarding the usefulness of the repeated attempts by governments to curb Cryptography (aka the ``Crypto Wars\u27\u27), and argue that they, in fact, cause more damage than adding effective control. The notion of Anamorphic Encryption was presented in Eurocrypt \u2722 for a similar aim. There, despite the presence of a Dictator who possesses all keys and knows all messages, parties can arrange a hidden ``anamorphic\u27\u27 message in an otherwise indistinguishable from regular ciphertexts (wrt the Dictator). In this work, we postulate a stronger cryptographic control setting where encryption does not exist (or is neutralized) since all communication is passed through the Dictator in, essentially, cleartext mode (or otherwise, when secure channels to and from the Dictator are the only confidentiality mechanism). Messages are only authenticated to assure recipients of the identity of the sender. We ask whether security against the Dictator still exists, even under such a strict regime which allows only authentication (i.e., authenticated/ signed messages) to pass end-to-end, and where received messages are determined by/ known to the Dictator, and the Dictator also eventually gets all keys to verify compliance of past signing. To frustrate the Dictator, this authenticated message setting gives rise to the possible notion of anamorphic channels inside signature and authentication schemes, where parties attempt to send undetectable secure messages (or other values) using signature tags which are indistinguishable from regular tags. We define and present implementation of schemes for anamorphic signature and authentication; these are applicable to existing and standardized signature and authentication schemes which were designed independently of the notion of anamorphic messages. Further, some cornerstone constructions of the foundations of signatures, in fact, introduce anamorphism

The Proceedings of the 23rd Annual International Conference on Digital Government Research (DGO2022) Intelligent Technologies, Governments and Citizens June 15-17, 2022

The 23rd Annual International Conference on Digital Government Research theme is “Intelligent Technologies, Governments and Citizens”. Data and computational algorithms make systems smarter, but should result in smarter government and citizens. Intelligence and smartness affect all kinds of public values - such as fairness, inclusion, equity, transparency, privacy, security, trust, etc., and is not well-understood. These technologies provide immense opportunities and should be used in the light of public values. Society and technology co-evolve and we are looking for new ways to balance between them. Specifically, the conference aims to advance research and practice in this field. The keynotes, presentations, posters and workshops show that the conference theme is very well-chosen and more actual than ever. The challenges posed by new technology have underscored the need to grasp the potential. Digital government brings into focus the realization of public values to improve our society at all levels of government. The conference again shows the importance of the digital government society, which brings together scholars in this field. Dg.o 2022 is fully online and enables to connect to scholars and practitioners around the globe and facilitate global conversations and exchanges via the use of digital technologies. This conference is primarily a live conference for full engagement, keynotes, presentations of research papers, workshops, panels and posters and provides engaging exchange throughout the entire duration of the conference

Cyber Threat Intelligence Exchange

The processing and exchange of Cyber Threat Intelligence (CTI) has become an increas- ingly important topic in recent years. This trend can be attributed to various factors. On the one hand, the exchange of information offers great potential to strengthen the knowledge base of companies and thus improve their protection against cyber threats. On the other hand, legislators in various countries have recognized this potential and translated it into legal reporting requirements. However, CTI is still a very young research area with only a small body of literature. Hence, there are hardly any guidelines, uniform standards, or specifications that define or support such an exchange. This dissertation addresses the problem by reviewing the methodological foundations for the exchange of threat intelligence in three focal areas. First, the underlying data formats and data structures are analyzed, and the basic methods and models are developed. In the further course of the work, possibilities for integrating humans into the analysis process of security incidents and into the generation of CTI are investigated. The final part of the work examines possible obstacles in the exchange of CTI. Both the legal environment and mechanisms to create incentives for an exchange are studied. This work thus creates a solid basis and a structured framework for the cooperative use of CTI