Tesis doctoral de Alexandre Ruiz Rodriguez
Nowadays people are involved in different digital activities in their professional life as well as in their private life. Many paper items, such as money and tickets, are more and more being replaced with digital objects. Cryptography plays a crucial role in this transformation, because it provides security in the communication between the different players using a digital channel. Depending on the specific situation, some security requirements in the communication can include privacy (or confidentiality), authentication, integrity or non-repudiation. In some situations, spreading the secret operation among a group of parties makes the process more secure and reliable than when the secret information is centralized in one single party; distributed cryptography is the area of cryptography that studies these situations. the present thesis deals with primitives related to the field of distributed cryptography. First, we study signcryption schemes, which provide at the same time the functionalities of encryption and signature, where the unsigncryption operation is distributed. We consider this primitive from a theoretical point of view and set a security framework for it. Then, we present two signcryption schemes with threshold unsigncryption, with different properties. Furthermore, we use their authenticity property to apply them in the development of a different primitive: digital signatures with distributed verification. The second block of the thesis deals with the primitive of multi-secret sharing schemes. After stating some efficiency limitations of multi-secret sharing schemes in an information-theoretic scenario, we present several multi-secret sharing schemes with provable computational security. Finally, we use the results in multi-secret sharing schemes to generalize the traditional framework of distributed cryptography (with a single policy of authorized subsets) into a multi-policy setting, and we present both a multi-policy distributed decryption scheme and a multi-policy distributed signature scheme. Additionally, we give a short outlook on how to apply the presented multi-secret sharing schemes in the design of other multi-policy cryptosystems, like the signcryption schemes considered in this thesis. for all the schemes proposed throughout the thesis, we follow the same formal structure. After defining the protocols of the primitive and the corresponding security model, we propose the new scheme and formally prove its security, by showing a reduction to some computationally hard mathematical problem.
Datos académicos de la tesis doctoral «Contributions to secret sharing and other distributed cryptosystems«
- Título de la tesis: Contributions to secret sharing and other distributed cryptosystems
- Autor: Alexandre Ruiz Rodriguez
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 22/07/2013
Dirección y tribunal
- Director de la tesis
- Javier Herranz Sotoca
- Tribunal
- Presidente del tribunal: vanessa Daza fernandez
- michel Abdalla (vocal)
- (vocal)
- (vocal)