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Deim Seminar


On the optimization of non-perfect secret sharing schemes


Torben Hansen

Professor/a organitzador/a

Oriol Farrs


Aarhus University


19-12-2013 12:00


A secret sharing scheme is a method to protect data by dividing it into pieces. These pieces are called shares and are generated in such a way that data can only be fully recovered from certain subsets. Secret sharing is an important primitive in cryptography, and its security is unconditional, it derives from information theory The first secret sharing schemes were constructed by Shamir and Blakley in 1979. The original motivation was to protect keys and to safeguard information, and so the shares were sent to a set of participants. The subsets of participants whose shares can generate the secret, are called authorized. In a perfect secret sharing scheme, the subsets that are not authorized cannot obtain any information about the secret. Because of that, the length of every share is at least the length of the secret. Non-perfect secret sharing schemes are schemes in which some non-authorized subsets may obtain partial information about the secret value. These schemes were first considered by Blakley and Meadows, who introduced the threshold non-perfect secret sharing schemes, also called ramp schemes. Differently to the perfect case, in a non-perfect secret sharing scheme the length of some shares may be smaller than the length of the secret, and so using these schemes we can construct more efficient cryptographic protocols. This talk will be dedicated to new results on the size of the shares of non-perfect secret sharing schemes. Torben Hansen is a master student of mathematics from the University of Aarhus, Denmark, and he is visiting the URV.


Lab 231 (a confirmar)