PLCrypto: A Symmetric Cryptographic Library for Programmable Logic Controllers

Programmable Logic Controllers (PLCs) are control devices widely used in industrial automation. They can be found critical infrastructures like power grids, water systems, nuclear plants, manufacturing etc. This paper introduces PLCrypto, a software cryptographic library that implements lightweight symmetric algorithms for PLCs using standard PLC programming language called structured text (ST). To the best of our knowledge, PLCrypto is first ST-based executable on commercial off-the-shelf PLCs. includes wide range commonly algorithms, totaling ten including one-way functions, message authentication codes, hash block ciphers, and pseudo-random functions/generators. to protect confidentiality integrity data without additional hardware or firmware modification. also presents general optimization methodologies techniques implementing primitive operations bit-shifting/rotation, substitution, permutation. The tricks we distilled from practice guide future implementation other computationheavy programs demonstrate use case practice, further realize protocol proof aliveness as study. We benchmarked protocols PLC, Allen Bradley ControlLogix 5571, which real world. Also, make source codes publicly available, so plant operators freely deploy practice.