TL
T. Li
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1
Privacy Preserving Train Scheduling
Using homomorphic encryption to create train schedules
A substantial number of passengers in Europe rely on trains for transportation, facilitated by a network of high-speed international trains. However, the coordination of train schedules across multiple networks often poses challenges due to incompatible timings. The scheduling of multiple train networks shares similarities with multi-processor task scheduling and airline scheduling but is distinguished by its cooperative nature rather than a competitive one. Cooperative scheduling necessitates the sharing of private information. This information, 'demand', is commercial sensitive information, since it can reveal demographic information like incomes and tax returns. Privacy-preserving protocols can enable the computation of statistics without revealing this demands (in railway systems) to unauthorized parties. Despite the critical role of privacy in multi-party scheduling, research in this domain remains limited due to domain specific constraints. A model supporting such privacy considerations could significantly help Europe achieve its carbon-neutral goals while improving cross-border services. In this research, we propose a system designed to facilitate joint service scheduling, ensuring confidentiality, integrity, and authenticity. We use partial and fully homomorphic encryption techniques that mimic the outcomes achievable with a trusted third party. We conduct a comparative analysis of online and offline approaches, emphasizing how they achieve confidentiality, collusion-resistance, traceability and non-repudiation. Theoretical and experimental evaluations demonstrate the feasibility of the system for real-world applications by creating schedules for upto four parties. Our solution for scheduling seven slots takes approximately three hours, which is a feasible duration to solve a problem of this size.
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A substantial number of passengers in Europe rely on trains for transportation, facilitated by a network of high-speed international trains. However, the coordination of train schedules across multiple networks often poses challenges due to incompatible timings. The scheduling of multiple train networks shares similarities with multi-processor task scheduling and airline scheduling but is distinguished by its cooperative nature rather than a competitive one. Cooperative scheduling necessitates the sharing of private information. This information, 'demand', is commercial sensitive information, since it can reveal demographic information like incomes and tax returns. Privacy-preserving protocols can enable the computation of statistics without revealing this demands (in railway systems) to unauthorized parties. Despite the critical role of privacy in multi-party scheduling, research in this domain remains limited due to domain specific constraints. A model supporting such privacy considerations could significantly help Europe achieve its carbon-neutral goals while improving cross-border services. In this research, we propose a system designed to facilitate joint service scheduling, ensuring confidentiality, integrity, and authenticity. We use partial and fully homomorphic encryption techniques that mimic the outcomes achievable with a trusted third party. We conduct a comparative analysis of online and offline approaches, emphasizing how they achieve confidentiality, collusion-resistance, traceability and non-repudiation. Theoretical and experimental evaluations demonstrate the feasibility of the system for real-world applications by creating schedules for upto four parties. Our solution for scheduling seven slots takes approximately three hours, which is a feasible duration to solve a problem of this size.
Third-party verified credentials (e.g. passports, diplomas) are essential in our daily life. The usage of third-party verified credentials bring us convenience in authentication. The Verifiable Credential (VC) data model is a new standard proposed by the W3C association to ease the expression and verification of third-party verified credentials on the Internet. The issuance and presentation of verifiable credentials are tamper-evident and privacy-preserving by design. However, the current verifiable credential data model lacks an explicit revocation design that guarantees the secure operations of the system. The lack of a revocation mechanism significantly limits the application of verifiable credentials. This thesis studies the revocation mechanisms of existing verifiable credential implementations. The existing revocation mechanisms are either tamper-evident or privacy-preserving. None of them can achieve the two properties together. To evolve the revocation mechanism to be both tamper-evident and privacy-preserving by design, we propose a new method which combines the BBS+ signature, a cryptographic accumulator and the blockchain. Our design enables the verifier to verify the presented credential’s revocation status without compromising the credentials holders’ privacy. We implement a proof-of-concept of our revocation mechanism to show it is practical in the real world. The experimental results show that after adding our revocation mechanism, the presentation time of a five-attribute credential changes from 22.22ms to 62.11ms (+39.89ms), and the verification time changes from 13.36ms to 44.56ms (+31.86ms). Moreover, the scalability analysis shows that our revocation mechanism can satisfy the need for revocation in the real world.
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Third-party verified credentials (e.g. passports, diplomas) are essential in our daily life. The usage of third-party verified credentials bring us convenience in authentication. The Verifiable Credential (VC) data model is a new standard proposed by the W3C association to ease the expression and verification of third-party verified credentials on the Internet. The issuance and presentation of verifiable credentials are tamper-evident and privacy-preserving by design. However, the current verifiable credential data model lacks an explicit revocation design that guarantees the secure operations of the system. The lack of a revocation mechanism significantly limits the application of verifiable credentials. This thesis studies the revocation mechanisms of existing verifiable credential implementations. The existing revocation mechanisms are either tamper-evident or privacy-preserving. None of them can achieve the two properties together. To evolve the revocation mechanism to be both tamper-evident and privacy-preserving by design, we propose a new method which combines the BBS+ signature, a cryptographic accumulator and the blockchain. Our design enables the verifier to verify the presented credential’s revocation status without compromising the credentials holders’ privacy. We implement a proof-of-concept of our revocation mechanism to show it is practical in the real world. The experimental results show that after adding our revocation mechanism, the presentation time of a five-attribute credential changes from 22.22ms to 62.11ms (+39.89ms), and the verification time changes from 13.36ms to 44.56ms (+31.86ms). Moreover, the scalability analysis shows that our revocation mechanism can satisfy the need for revocation in the real world.