Attribute-based digital signatures

Abstract

An attribute-based digital signature system is disclosed. A first signature generating unit (1) is used for generating a first signature (10) for a document (11), based on a first signature key (12) and the document (11). A re-signing unit (2) is used for generating a second signature (13) for the document (11), based on the first signature (10) and a re-signing key (14), wherein the re-signing unit (2) is arranged for handling attributes (15, 16) associated with the first signature (10) and/or the second signature (13). The second signature (13) is associated with a second set of attributes (16,16′) determined by the re-signing key (14), wherein the second set of attributes (16) comprises a plurality of attributes. The first signature (10) is associated with a first set of attributes (15), wherein the first set of attributes (15) comprises a plurality of attributes, and the re-signing unit (2) is arranged for generating the second signature (13) only if the first set of attributes (15) satisfies a set of conditions (17, 17′).

Dependencies are inferred from the claim text.