Abstract
We introduce Attribute-Based Signatures with Controllable Linkability ABS-CL. In general, Attribute-Based Signatures allow a signer who possesses enough attributes to satisfy a predicate to sign a message without revealing either the attributes utilized for signing or the identity of the signer. These signatures are an alternative to Identity-Based Signatures for more fine-grained policies or enhanced privacy. On the other hand, the Controllable Linkability notion introduced by Hwang et al. [14] allows an entity in possession of the linking key to determine if two signatures were created by the same signer without breaking anonymity. This functionality is useful in applications where a lower level of anonymity to enable linkability is acceptable, such as some cases of vehicular ad-hoc networks, data mining, and voting schemes. The ABS-CL scheme we present allows a signer with enough attributes satisfying a predicate to sign a message, while an entity with the linking key may test if two such signatures were created by the same signer, all without revealing the satisfying attributes or the identity of the signer.