Abstract—GMSCF is a variant of multicast generalized signcryption designed for the authentication of messages in multi mode i.e. encryption only mode, signature only mode and signcryption only mode. These multimode messages are verified by the firewall before communicating to the multi receiver. In this paper, we propose a novel multi receiver generalized signcryption scheme based on elliptic curve for firewalls where FVerify algorithm is used for the verification of the multi mode messages. The correctness, security and cost analysis of the proposed scheme is presented which prove the security and efficiency of the scheme. Keywords— Multicast; Generalized Signcryption; Encrypted Message Authentication 1. INTRODUCTION Multicast is an emerging for group communication. In 1997, Zheng [1] coined the concept of signcryption with target to reduce the simultaneous cost of encryption and signature. In 1998 Zheng [2] extended the concept of signcryption for multi receiver. In [3][4][5][6][7] proposed signcryption schemes used authenticated key agreement, forward secrecy and public verifiability working in a single mode for single recipient. In Multicast Generalized Signcryption (MGSC), one algorithm works in multi mode i.e. signcryption only mode, encryption only mode or signature only mode with the idea to reduce memory usage. MGSC scheme works in signcryption only mode, if confidentiality and authenticity are required and works in encryption only mode or signature only mode if one of them is required. Though multicast signcryption schemes are efficient, but not be feasible when only one of three functions: confidentiality, authenticity or confidentiality and authenticity are required. In 2006 Han et al. [8] proposed ECGSC: Elliptic Curve based generalized signcryption scheme and Zhang et al [9] and Wang et al [10] posed an attack on the confidentiality of GSC in signcryption-mode and proposed an improved GSC with formal security proofs. Chuanrong et al. [11] proposed a scheme providing properties of forward secrecy and message public verification. In 2007, Han [12] first proposed a MGSC scheme in the Random Oracle model. But this scheme lacks the functionality of signature only mode. Yang et al. [13] proposed MGSC on ECDLP that can adaptively work as multi receiver signcryption, multi receiver encryption or signature but this scheme lacks confidentiality, which is the important security feature. In 2009, Han and Gui’s [14] proposed a MGSC scheme under the Computational Diffie Hellman(CDH) assumption and covered the confidentiality. Caixue Zhou [15] shows that Han and Gui’s [14] MGSC scheme is not IND-CCA2 secure in pure encryption mode and hybrid encryption mode and gave an improvement of their scheme, secure under the CDH assumption. And Caixue Zhou [16] proposed first identity-based based generalized multi- receiver signcryption. We proposed first secure MGSCF in public key infrastructure based on ECC and ciphertext verifiable in three different modes that can be used in firewall implementation. The correctness, security and cost of the proposed scheme are evaluated which shows the obvious improvement of our scheme. 2. PRELIMINARIES This section, briefly describes the basic notations and definitions used throughout the paper. Let  be a large prime number, where     and   is a finite field of order . An Elliptic curve    over finite field   Notations:   : A base point of elliptic curve with order     : Private key of the sender    : Public key of the sender    : Private key of receiver      , where  number of receiver    : Public key of receiver    : One-way hash function      : Symmetric encryption/decryption algorithm using key    : Number of receiver     : Message / Ciphertext    : Encrypted session key  : The message is not properly encrypted or signed GMSCF: An Efficient Generalization of Multicast Signcryption Based on Elliptic Curve for Firewalls Nizamud Din *+ , Arif Iqbal Umar * , Abdul Waheed * , Noor ul Amin * , Muazzam A. Khan ** * Department of Information Technology, Hazara University Mansehra Pakistan + Department of Computer Science, IQRA National University, Peshawar ** College of EME, National University of Sciences and Technology (NUST), Islamabad International Journal of Computer Science and Information Security (IJCSIS), Vol. 14, No. 5, May 2016 432 https://sites.google.com/site/ijcsis/ ISSN 1947-5500