  Industrial Ethernet is a technology widely spread in factory floors and
critical infrastructures where a high amount of data need to be collected and
transported. Fiber optic networks at gigabit rates fit well with that type of
environments where speed, system performance and reliability are critical. In
this work a new encryption method for high speed optical communications
suitable for such kind of networks is proposed. This new encryption method
consists of a symmetric streaming encryption of the 8b/10b data flow at PCS
(Physical Coding Sublayer) level. It is carried out thanks to an FPE (Format
Preserving Encryption) blockcipher working in CTR (Counter) mode. The overall
system has been simulated and implemented in an FPGA (Field Programmable Gate
Array). Thanks to experimental results it can be concluded that it is possible
to cipher traffic at this physical level in a secure way. In addition, no
overhead is introduced during encryption, getting minimum latency and maximum
throughput.
