Secure Trust Transfer Using Chain Signatures

Abstract

In this chapter, we discuss the concept of “trust transfer” using chain signatures. Informally, transferring trust involves creating a trust (or liability) relationship between two entities such that both parties are liable in the event of a dispute. If such a relationship involves more than two users, we say they are connected in a chained trust relationship. The members of a chained trust relationship are simultaneously bound to an agreement with the property that additional members can be added to the chain but once added, members cannot be removed thereafter. This allows members to be incrementally and noninteractively added to the chain. We coin the term “chained signatures” to denote signatures created in this incremental way. An important application of chained signatures is in e-commerce transactions involving many users. We present a practical construction of such a scheme that is secure under the Diffie- Hellman assumption in bilinear groups.