Pipelined Statistical Cipher Feedback: A New Mode for High-Speed Self-Synchronizing Stream Encryption

Abstract

In this paper, we introduce a new block cipher mode of operation targeted to providing high-speed hardware-based self-synchronizing stream encryption. The proposed mode is a modification of statistical cipher feedback (SCFB) mode and is designed to be implemented using pipeline architectures for the block cipher. We refer to the mode as pipelined SCFB mode or PSCFB. In this paper, we consider the implementation characteristics and show that PSCFB is able to achieve speeds that are very close to pipelined block cipher implementations configured for counter mode. Such speeds are achieved with modest latency through the system and a small amount of memory required for the system queues with a provable guarantee of no queue overflow. Further, we examine the characteristics of PSCFB mode in response to bit errors and synchronization losses in the communication channel. Specifically, we show that the error propagation factor is modest and comparable to conventional SCFB and that synchronization recovery delay is reasonable given the expectation that synchronization loss is infrequent. Given the high efficiency and good communication characteristics of the mode, it is concluded that PSCFB is an excellent choice for high-speed network applications requiring stream-oriented encryption with self-synchronizing capabilities.