human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "Structure-preserving signatures and commitments to group elements"
  Abstract: A modular approach for cryptographic protocols leads to a simple design but often inefficient constructions. On the other hand, ad hoc constructions may yield efficient protocols at the cost of losing conceptual simplicity. We suggest structure-preserving commitments and signatures to overcome this dilemma and provide a way to construct modular protocols with reasonable efficiency, while retaining conceptual simplicity.

We focus on schemes in bilinear groups that preserve parts of the group structure, which makes it easy to combine them with other primitives such as non-interactive zero-knowledge proofs for bilinear groups.

We say that a signature scheme is structure-preserving if its verification keys, signatures, and messages are elements in a bilinear group, and the verification equation is a conjunction of pairing-product equations. If moreover the verification keys lie in the message space, we call them automorphic. We present several efficient instantiations of automorphic and structure-preserving signatures, enjoying various other additional properties, such as simulatability. Among many applications, we give three examples: adaptively secure round-optimal blind signature schemes, a group signature scheme with efficient concurrent join, and an efficient instantiation of anonymous proxy signatures.

A further contribution is homomorphic trapdoor commitments to group elements which are also length reducing. In contrast, the messages of previous homomorphic trapdoor commitment schemes are exponents.

Connected through hyperedge HE-1 (induced by source paper "Authenticating Computation on Groups: New Homomorphic Primitives and Applications"):
  with members:
    - "Signing on Elements in Bilinear Groups for Modular Protocol Design."
    - "More Efficient Constant-Round Multi-party Computation from BMR and SHE"

Connected through hyperedge HE-2 (induced by source paper "Signing on Elements in Bilinear Groups for Modular Protocol Design."):
  with members:
    - "Authenticating Computation on Groups: New Homomorphic Primitives and Applications"

Connected through hyperedge HE-3 (induced by source paper "Efficient Signatures with Tight Real World Security in the Random-Oracle Model"):
  with members:
    (none)

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Mathematics