A Secure Group Communication and Rekeying using Rabin’s Squaring Trapdoor Function in Multicasting

In today‟s world of internet, secure communication among group of members has become vital, where multicasting plays an important role. In secure multicasting, security and scalability are the two important checks. Sometimes there is tradeoff between security and scalability. In order to transmit the data in a secure and scalable way, a suitable key management protocol should be implemented which reduces the number of rekey messages generated during the join or leave of any member thereby preserving forward and backward secrecy. In our proposed work, a new key management protocol has been proposed where a hierarchical structure has been implemented to improve the scalability. Derivation key is used to generate the new keys from the existing keys and Rabin‟s Squaring Trapdoor Function is used as the key derivation function to distribute the rekey messages. The security of the key derivation function lies in the hard mathematical problem of integer factorization which cannot be solved in a polynomial time. In order to increase the security, a salt value has been used along with the derivation keys for key stretching so that original keys used in the derivation function cannot be found out. The proposed protocol reduces the rekey messages by 1/d, in a d-degree tree and the number of modular exponential operations is only 2h compared to 3h in TGDH (Tree-based Group Diffie-Hellman) protocol, where h is the height of the tree.