302 Int. J. Information and Communication Technology, Vol. 2, No. 4, 2010 Copyright © 2010 Inderscience Enterprises Ltd. Efficient key management FPGA-based cryptosystem using the RNS and iterative coding N. Ntomambang Ningo ACL, ENSP, University of Yaoundé 1, P.O. Box 8370, Yaounde, Cameroon E-mail: ndeh.ningo@yahoo.com M. Ekonde Sone* Faculty of Science, University of Buea, P.O. Box 63, Buea, Cameroon E-mail: ekonde.sone@gmail.com *Corresponding author Abstract: The paper reports the development of a new cryptosystem with a multilevel structure for encryption and decryption. At the first level, RNS-based implementation of a public-key RSA signature converts the original plaintext into a ciphertext. Iterated wavelet-based subband coding splits the ciphertext into different levels of decomposition. At subsequent levels of decomposition, the ciphertext from the preceding level serves as plaintext for encryption using convolutional codes. Attack is difficult since the cryptographic complexity is propagated from one level of decomposition to another. By using the RNS, there is efficient key management since long secret keys are replaced by short parallel keys which depend on the residue set. Moduli set {111, 115, 119} is used to implement a multilevel non-linear (8, 8, 2) two-cascaded model on a Virtex-4 FPGA. To our knowledge, this is the first proposal of a hardware implementation of a cryptosystem using lossless compression and convolutional codes. Keywords: subband coding; SBC; convolutional codes; ciphertext; moduli set; field-programmable gate array; FPGA; residue number system; RNS; very-high-speed hardware description language; VHDL; Rivest, Shamir and Adleman cryptosystem; RSA. Reference to this paper should be made as follows: Ningo, N.N. and Sone, M.E. (2010) ‘Efficient key management FPGA-based cryptosystem using the RNS and iterative coding’, Int. J. Information and Communication Technology, Vol. 2, No. 4, pp.302–322. Biographical notes: N. Ntomambang Ningo received his PhD from Rensselaer Polytechnic Institute in Troy, New York in 1982. He is currently a Lecturer at the ‘Ecole Nationale Superieure Polytechnique’ of the University of Yaounde 1, Cameroon and the Head Scientist of the Automation and Control Laboratory (ACL) of the same institution. His research interests include signal detection and computer networks.