A Stream Cipher Model for Hardware Constraint Environments

In this study by inspiring from use of error correcting codes in communications, we propose a new stream cipher model which contradicts with the argument -- a known plaintext/ciphertext pair explicitly gives corresponding keystream block -- for binary additive stream ciphers. According to this model, the transmitter produces a nondeterministic keystream, composed of two sequences as the deterministic and the nondeterministic sequences. The receiver can perfectly decrypt the message without knowledge of the nondeterministic component, whereas it turns out to be hard problem for a cryptanalyst who intends to obtain the deterministic part though corresponding  plaintext/ciphertext pair is available to him. Indeed, this is the prominent property of the model and we show that it enhances the security of the scheme against non tolerant attacks. In addition, we give a tradeoff between Hardware Area Cost (HAC) and information rate for the proposed model. Hence, we consider this issue in the remaining part of the work and construct a tradeoff between HAC and information rate. We show that it is possible to decrease the threshold for HAC, without undermining the security level, at a cost of increasing the communication overhead. This tradeoff can provide efficient solutions in resource constrained environments such as RFID tags.