International Association for Cryptologic Research

Ph.D. Database

The aim of the IACR Ph.D. database is twofold. On the first hand, we want to offer an overview of Ph.D. already completed in the domain of cryptology. Where possible, this should also include a subject classification, an abstract, and access to the full text. On the second hand, it deals with Ph.D. subjects currently under investigation. This way, we provide a timely map of contemporary research in cryptology. All entries or changes need to be approved by an editor. You can contact them via phds (at)


Ruxandra F. Olimid (#984)
Name Ruxandra F. Olimid
Personal Homepage
Topic of his/her doctorate. Secret Sharing-based Group Key Establishment
Category (no category)
Keywords key management, secret sharing, cryptanalysis
Ph.D. Supervisor(s) Adrian Atanasiu
Year of completion 2013
Abstract Group applications permit multiple users to share resources or perform collaborative tasks while providing differentiate rights or responsibilities within the group. Examples include text communication, audio, video or web conferences, data sharing or collaborative computing.
Security represents an important aspect for group applications. It is a challenging task to deal with, especially when the group size is large and the members are spread across different (location or networks) areas, with diverse protection mechanisms. In order to obtain the main cryptographic properties as confidentiality, authenticity and integrity it is usually required that the group members previously share a common secret group key. This is achieved as theoutput of a group key establishment protocol.
The thesis restricts to group key establishment protocols based on secret sharing, a primitive that divides a secret into multiple shares such that only authorized subset of shares allow reconstruction. Although secret sharing brings several advantages when it is used as a building block of group key establishment protocols, two important shortcomings currently exist: (1) several insecure proposals were published in the last years and (2) very few constructions rely on a security proof. We address both this issues in the present work.
The first part of the dissertation focuses on the underlying secret sharing schemes. We review a non-classical approach of secret sharing, de ne a new visual secret sharing scheme and analyze the possibility of malicious manufacturing of the sharing device. The second part of the thesis concentrates on group key establishment constructions that use secret sharing. We introduce a multitude of attacks against recent protocols and therefore highlight the necessity of security proofs. We review the properties that impose a sufficient level of security and briefly analyze the formal models of security. Finally, we introduce a new provable secure group key establishment protocol that achieves a good level of security while it maintains a constant number of communication rounds regardless the group size.
E-Mail Address ruxandra.olimid (at)
Last Change 2014-01-26 07:58:39
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