Sanitizable Signatures with Different Admissibility Policies for Multiple Sanitizers

Sanitizable signatures authorize semi-trusted sanitizers to modify admissible blocks of a signed message. Most works consider only one sanitizer while those considering multiple sanitizers are limited by their capacity to manage admissible blocks which must be the same for all of them. We study the case where different sanitizers with different roles can be trusted to modify different blocks of the message. We define a model for multi-sanitizer sanitizable signatures which allow managing authorization for each sanitizer independently. We also provide formal definitions of its security properties. We propose two secure generic constructions FSV-k-SAN and IUT-k-SAN with different security properties. We implement both constructions and evaluate their performance on a server and a smartphone.