# Potential of Homomorphic Encryption for Cloud Computing Use Cases in Manufacturing
## 5 Conclusions and Outlook  
This paper evaluated the potential of homomorphic encryption for cloud computing use cases in manufacturing. After presenting the fundamentals in Section 2, Section 3 presented encryption for cloud computing, analyzing the limitations of classic encryption, as well as the potential and challenges of homomorphic encryption. This showed that homomorphic encryption has a big advantage regarding security over the whole data lifecycle, but has the consequence of higher computing times, thus leading to higher computing energy and costs. However, the section also showed that the potential and challenges of homomorphic encryption highly depend on the use case. Therefore, Section 4 identified use cases for homomorphic encryption for cloud computing in manufacturing and analyzed how homomorphic encryption improves this use case. This showed that, in general, several beneficial manufacturing use cases exist. However, mainly FHE and SWHE methods are applicable in manufacturing. Furthermore, it is probably only beneficial if using public or community clouds, as private clouds generally fulfill security requirements per se; thus, using homomorphic encryption does not have any further benefits. Sections 3.3 and 4 represented the main contribution and novelty of this paper, as this paper is the first to simulate homomorphic encryption applicability for manufacturing and present in detail manufacturing use cases on the level of data transfer. Despite the shown potential of homomorphic encryption for manufacturing, there is further research necessary to increase the use of homomorphic encryption in manufacturing. For increased use in manufacturing, the development of efficient manufacturing specific FHE methods is necessary, which offer correspondingly extensive functionality, but entail less computing time and reduced costs in the application. For this purpose, the specific requirements of manufacturing applications could first be determined, which can be sensibly outsourced to a cloud. This includes, e.g., the definition of error threshold of the bootstrapping for manufacturing, as well as necessary operations other than addition and multiplication. Furthermore, a tradeoff between the use of cloud computing and data security should take place for the consideration of the topic. A mathematical modeling could be envisaged, which weighs the additional effort caused by homomorphic encryption against the advantages of cloud computing. In this way, the decision on the use of homomorphic encryption could be systematized and, thus, facilitated. Interesting developments also exist around business models and current implementation of homomorphic encryption. For example, IBM offers so-called homomorphic encryption services. This is a service offering that includes the option of using a fully homomorphic encryption process [49]. Research in this area could be further expanded in the future and continued by other companies. On the other hand, many public libraries already exist, such as SEAL or HElib, which can be used to implement homomorphic encryption [50]. At this point, another property of homomorphic encryption should be mentioned that might become relevant in the context of cryptographic security in the future. FHE theoretically provides complete security with respect to the threats posed by the advancement and improvement of quantum computers. The development of viable homomorphic encryption systems may, therefore, offer important advantages for the future of cryptography [29]. Conceptualization, R.K., M.L. and K.L. ; methodology, R.K. and M.L. ; software, A.M.; validation, A.M., R.K. and M.L. ; writing--original draft preparation, R.K. and M.L. ; writing--review and editing, K.L., F.S. and R.H.S. ; visualization, R.K.; supervision, R.H.S. All authors read and agreed to the published version of the manuscript. This research received no external funding. Not applicable.