Privacy-Preserving Electronic Ticket Scheme with Attribute-based Credentials

Electronic tickets (e-tickets) are electronic versions of paper tickets, which enable users to access intended services and improve services' efficiency. However, privacy may be a concern of e-ticket users. In this paper, a privacy-preserving electronic ticket scheme with attribute-based credentials is proposed to protect users' privacy and facilitate ticketing based on a user's attributes. Our proposed scheme makes the following contributions: (1) users can buy different tickets from ticket sellers without releasing their exact attributes; (2) two tickets of the same user cannot be linked; (3) a ticket cannot be transferred to another user; (4) a ticket cannot be double spent; (5) the security of the proposed scheme is formally proven and reduced to well known (q-strong Diffie-Hellman) complexity assumption; (6) the scheme has been implemented and its performance empirically evaluated. To the best of our knowledge, our privacy-preserving attribute-based e-ticket scheme is the first one providing these five features. Application areas of our scheme include event or transport tickets where users must convince ticket sellers that their attributes (e.g. age, profession, location) satisfy the ticket price policies to buy discounted tickets. More generally, our scheme can be used in any system where access to services is only dependent on a user's attributes (or entitlements) but not their identities.Comment: 18pages, 6 figures, 2 table

Anonymous Single-Sign-On for n designated services with traceability

Anonymous Single-Sign-On authentication schemes have been proposed to allow users to access a service protected by a verifier without revealing their identity. This has become more important with the introduction of strong privacy regulations. In this paper we describe a new approach whereby anonymous authentication to different verifiers is achieved via authorisation tags and pseudonyms. The particular innovation of our scheme is that authentication can occur only between a user and its designated verifier for a service, and the verification cannot be performed by any other verifier. The benefit of this authentication approach is that it prevents information leakage of a user's service access information, even if the verifiers for these services collude. Our scheme also supports a trusted third party who is authorised to de-anonymise the user and reveal her whole service access information if required. Furthermore, our scheme is lightweight because it does not rely on attribute or policy-based signature schemes to enable access to multiple services. The scheme's security model is given together with a security proof, an implementation and a performance evaluation

A Symbolic Analysis of ECC-based Direct Anonymous Attestation

Direct Anonymous Attestation (DAA) is a cryptographic scheme that provides Trusted Platform Module (TPM)- backed anonymous credentials. We develop TAMARIN modelling of the ECC-based version of the protocol as it is standardised and provide the first mechanised analysis of this standard. Our analysis confirms that the scheme is secure when all TPMs are assumed honest, but reveals a break in the protocol’s expected authentication and secrecy properties for all TPMs even if only one is compromised. We propose and formally verify a minimal fix to the standard. In addition to developing the first formal analysis of ECC-DAA, the paper contributes to the growing body of work demonstrating the use of formal tools in supporting standardisation processes for cryptographic protocols

Anonymous Single Sign-on with Proxy Re-Verification

An anonymous single sign-on (ASSO) scheme allows users to access multiple services anonymously using one credential. We propose a new ASSO scheme, where users can access services anonymously through the use of anonymous credentials and unlinkably through the provision of designated verifiers. Notably, verifiers cannot link a user’s service requests even if they collude. The novelty is that when a designated verifier is unavailable, a central authority can authorize new verifiers to authenticate the user on behalf of the original verifier. Furthermore, a central verifier can also be authorized to de-anonymize users and trace their service requests. We formalize the scheme along with a security proof and provide an empirical evaluation of its performance. This scheme can be applied to smart ticketing where minimizing the collection of personal information of users is increasingly important to transport organizations due to privacy regulations such as general data protection regulations (GDPRs)

Formal Analysis and Implementation of a TPM 2.0-based Direct Anonymous Attestation Scheme

Direct Anonymous Attestation (Daa) is a set of cryptographic schemes used to create anonymous digital signatures. To provide additional assurance, Daa schemes can utilise a Trusted Platform Module (Tpm) that is a tamper-resistant hardware device embedded in a computing platform and which provides cryptographic primitives and secure storage. We extend Chen and Li’s Daa scheme to support: 1) signing a message anonymously, 2) self-certifying Tpm keys, and 3) ascertaining a platform’s state as recorded by the Tpm’s platform configuration registers (PCR) for remote attestation, with explicit reference to Tpm 2.0 API calls.We perform a formal analysis of the scheme and are the first symbolic models to explicitly include the low-level Tpm call details. Our analysis reveals that a fix proposed by Whitefield et al. to address an authentication attack on an Ecc-Daa scheme is also required by our scheme. Developing a finegrained, formal model of a Daa scheme contributes to the growing body of work demonstrating the use of formal tools in supporting security analyses of cryptographic protocols. We additionally provide and benchmark an open-source C++ implementation of this Daa scheme supporting both a hardware and a software Tpm and measure its performance

A Symbolic Analysis of ECC-based Direct Anonymous Attestation

Direct Anonymous Attestation (DAA) is a cryptographic scheme that provides Trusted Platform Module (TPM)- backed anonymous credentials. We develop TAMARIN modelling of the ECC-based version of the protocol as it is standardised and provide the first mechanised analysis of this standard. Our analysis confirms that the scheme is secure when all TPMs are assumed honest, but reveals a break in the protocol’s expected authentication and secrecy properties for all TPMs even if only one is compromised. We propose and formally verify a minimal fix to the standard. In addition to developing the first formal analysis of ECC-DAA, the paper contributes to the growing body of work demonstrating the use of formal tools in supporting standardisation processes for cryptographic protocols

Personalised rail passenger experience and privacy

In this article the authors discuss the implications of this data collection in terms of its potential benefits to the customer experience, its impact on passenger privacy, the information security risks to the industry from storing all this personal data as well as the need for data provenance and how anonymisation of data will impact its provenance and utility.It is imperative for the industry to look at the trade-offs between the need to store personal data to provide an improved customer service and the legal ramifications of doing so, especially in the light of the incoming General Data Protection Regulation (GDPR) [1] (to be enacted in UK law by May 2018) which makes organisations liable for a substantial fine in the case of a serious data security breach.To help operators address these data protection and legal compliance issues, the authors provide a brief overview of existing privacy and security frameworks, standards and guidelines which can assist the industry in utilising a best practice and well-established approach