A simple high-availability multiple-agent key recovery system

In symmetric cryptosystem, a session key is used for both message encryption and decryption. In case the session key is unavailable or legal investigation of transmitting messages is needed, an appropriate recovery mechanism is required. Key recovery can be achieved by a single agent or multiple agents. The latter can primarily enhance the security of the former by mitigating the risks of fabrication and collusion. The recovery of session key is usually provided by a trusted key recovery center (KRC) as a coordinator between key recovery agents (KRAs). This paper presents a key recovery system (SHAM-KRS) that has high availability. Since the session key can be recovered despite the failure of some key recovery agents, the problem of single point of failure can be avoided. It also has a feature to detect attacks on group authentication. Finally, it supports law enforcement needs and is based on the public key infrastructure.