Cloud data security is recognized as making the data confidential along with proper authentication. The Galois/Counter Mode (GCM) is used to provide data confidentiality with associated data as authentication. It aims to provide birthday bound security i.e. it is secure up to 2^(n/2) adversarial queries where n is a block size. But in some cases this much security is not sufficient. In this paper, we have proposed a new approach to authenticated encryption with associated data (AEAD), an improved AEAD scheme which can be secure up to approximately 2^n / p adversarial queries where, p = (n/m) , where n is a block size and m is a bit variance. This bit variance is introduced in the encryption process. In the proposed nonce-respecting AEAD scheme a new pseudorandom function is defined and used for implementation. To generate authentication tag universal hash function is used. In this paper security proofs of proposed scheme are given by presenting its construction and its security model.

Authenticated encryption with associated data, beyond birthday bound security, cloud data confidentiality, data authentication

[1] Chanathip Namprempre Mihir Bellare, "Authenticated Encryption: Relations among notions and analysis of the generic composition paradigm," Lecture Notes in Computer Science,Springer-Verlag, vol. 1976, pp. 531–545, July 2007.
[2] C. Jutla, "Encryption modes with almost free message integrity".
[3] V. Gligor and P. Donescu, "Fast encryption and authentication: XCBC encryption and XECB authentication modes.".
[4] M. Bellare, J. Black, andT. Krovetz P. Rogaway, "OCB: A block-cipher mode of operation for efficient authenticated encryption," 2001.
[5] Rogaway P., "Authenticated-Encryption with Associated-Data," in 9th ACM Conference on Computer and Communications Security, Washington,USA, 2002, pp. 98-107.
[6] A. Bogdanov, A. Luykx, B. Mennink, E. Tischhauser, and K. Yasuda E. Andreeva, "Parallelizable and authenticated online ciphers".
[7] S. Fluhrer, C. Forler F. Abed, "Pipelineable on-line encryption".
[8] C. Forler, and S. Lucks E. Fleischmann, "McOE: a family of almost foolproof on-line authenticated encryption schemes".
[9] M. Bellare and C. Namprempre, "Authenticated encryption: relations among notions and analysis of the generic composition paradigm".
[10] P.Jovanovic,B.Mennink,and S.Neves R.Granger, "Improved masking for tweakable blockciphers with applications to authenticated encryption".
[11] J.Viega D.A.McGrewand, "The security and performance of the Galois/counter mode (GCM) of operation".
[12] Dr. Vijay R. Ghorpade Rajani S. Sajjan, "AES-VR:A New Approach for Cloud Data Confidentiality," International Journal of Computer Technology and Applications, Accepted 2018.
[13] Hong-Gang Hu, Qian Yuan Ping Zhang, "Close to optimally secure variants of GCM," Hindawi, vol. 2018, March 2018.