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: "Rethinking Definitions of Security for Session Key Agreement."
  Abstract: We consider session key agreement (SKA) protocols operating in a public key infrastructure, with pre-specied peers, that take no session ID as input, and output only a session key. Despite much work on SKA, we argue that there is no good denition of security for this (very natural) protocol syntax. The diculty is that in this setting the adversary may not be able to tell which processes share a key, and thus which session keys may be revealed without trivializing the security condition. We consider security against adversaries that control all network trac, can register arbitrary public keys, and can retrieve session keys. We do not attempt to mitigate damage from hardware failures, such as session-state compromise, as we aim to improve our understanding of this simpler setting. We give two natural but substantially dierent game based denitions

Connected through hyperedge HE-1 (induced by source paper "Composability of bellare-rogaway key exchange protocols"):
  with members:
    - "Reconciling Two Views of Cryptography (The Computational Soundness of Formal Encryption)"

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: Computer science