Group based applications have gained popularity in recent years. As these applications typically involve communication over open network, security is an important requirement. Group key management is one of main block in securing group communication. Though, centralized and distributed group key schemes rely on at least one explicit key manager for generating traffic key, contributory schemes employ the contribution of all members of a group for initiating new traffic key. This work presents an

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... overview of existing contributory group key management schemes which specifically employ public key exchange algorithms for generating traffic key among members of a group. The initial operation which is used to generate first traffic key among members of group is demonstrated. Subsequently, required operations for provision of backward and forward secrecy during upon any changes in group membership are explored. And finally, the investigated schemes are analyzed and then compared in term of their communication cost. Index Terms-Group communication, group key managemen, cryptographic algorithms