Industry 4.0 will revolutionize industrial automation. Yet, future smart factories will not be created from scratch. They will rather evolve from existing legacy installations. Consequently, also industrial networks will evolve and the result will be a mixture of new and legacy components. This will make new security mechanisms necessary, that are specifically designed for this industrial use case. This work proposes modifications for MACsec [1], a new security protocol for protecting communication traffic. These modifications enable MACsec to work within future industrial settings, circumventing drawbacks introduced by legacy networking technologies. Furthermore, we managed to significantly increase the performance of MACsec.