Abstract: Transaction protocols and network applications are rapidly changing from a simple client-server model towards multi-party, multi�purpose, multi� device models. The main objective of a model of Multi-Party Security System (Multi-PaSS) provides the security services like Security infrastructure, supporting secure transactions between several parties in an open global environment with registration, certification, distributed remote authentication and trusted security administration, Secure multi-party protocolsfor protection of transactions in transfer, storage, authenticity delegation, authorization forwarding, etc. and Security extensions of various network applications suitable for multi-party transactions providing user authentication, cryptography, certification function, message protection, etc.. The structure of the Multi-PaSS may be shown in the form of three layers. The bottom layer, called security platform, contains cryptographic modules and security tokens, such as ATM cards. The middle layer comprises a collection of security proxies (Multi-PaSS proxies), which can securely communicate with each other performing security operations in a multi-party environment. The top layer, security infrastructure, comprises multiple cross-certified Public Key Infrastructure (Multi-PKI domains) and other supporting servers. All participants of a transaction must communicate through Multi-PaSS proxyservers and they handle authentication and all transactions between them. This authentication is performed using sequentialand parallelconcept. Since, MPT protocol messages contain corresponding timestamps, verifiers can verify creation time and verification time. Multiple signatures together with timestamps provide authenticity, integrity and non-repudiation security services for multi-party transactions.