Secure Stateless Trust Negotiation

Trust establishment is a challenge for services in distributed open environments. Trust Negotiation is a requirements- driven method for establishing trust between strangers and parties with limited mutual trust. Protocols for stateless trust negotiation use messages which contain the whole negotiation state. Stateless trust negotiation systems are advantageous in open environments due to their ability to recover from failures by simply processing the last message again. Furthermore stateless negotiation reduces resource consumption at the negotiating parties for long lasting negotiations. A drawback of stateless negotiation systems is that the complete negotiation state is prone to forgery by the other party in the negotiation. Stateless negotiation can not be used if it does not address this vulnerability. We propose a security extension to an existing XML based trust negotiation protocol in order to allow for secure stateless negotiations. Our novel alternating signature protocol detects manipulations of the negotiation state and introduces non- repudiation to agreements. Stateless trust negotiation extended with the alternating signature protocol can be a viable alternative to stateful negotiation approaches especially for long lasting negotiations in unreliable environments.