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  • 1 Department of Computeralgebra, Eötvös Loránd University
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In this paper we propose a decentralized privacy-preserving system which is able to share sensible data in a way, that only predefined subsets of authorized entities can recover the data after getting an additional alarm message. The protocol uses two main communication channels: a P2P network where the encrypted information is stored, and a smaller private P2P network, which consists of the authorized parties called friend-to-friend network. We describe the communication protocol fulfilling the desired security requirements. The proposed protocol achieves unconditional security. The main cryptographic building blocks of the protocol are symmetric encryption schemes and secret sharing schemes.

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