In this paper we apply techniques from secret sharing and threshold decryption to show how to properly design an ID-based
threshold system in which one assumes no trust in any party.
– We avoid that any single machine ever knew the master secret s of the trusted authority (TA). Instead only shares of it will be known by parties of the distributed TA and it can be seen as a virtual key.
–The threshold t
TA
and the number of shareholders n
TA
used by the distributed TA do not need to be identical to the ones used by user ID. Moreover, each user ID can use its own values for the threshold t
i
and the number of parties n
i
that will acquire shares.
–No single machine will ever know the secret key of the user – this means no single machine in the distributed TA and no shareholder
of the user ID and not ID itself.
Like Baek and Zheng suggest, such a scheme can be turned into a mediated system.
Keywords Threshold cryptography - Mediated system - Redistribution schemes - Secret sharing - ID-based cryptography - Pairings - Distributed keys