it – Information Technology 2018; 60(5-6): 283–291 Thomas Hepp*, Matthew Sharinghousen, Philip Ehret, Alexander Schoenhals, and Bela Gipp On-chain vs. of-chain storage for supply- and blockchain integration https://doi.org/10.1515/itit-2018-0019 Received July 14, 2018; accepted November 12, 2018 Abstract: Supply chains are the basis of most everyday life products. Both data integrity and authenticity of re- lated information have severe implications for quality and safety of end-products. Hence, tamper-proof storage is necessary that prevents unauthorized modifcations. We examine peer-reviewed blockchain technologies accord- ing to four criteria relevant to supply chains: On-chain storage, of-chain storage, verifcation cost and secure data sharing. Our evaluation yields an overview of concepts for modeling supply chain processes and points out that on- chain storage is currently not practical. Keywords: decentralized storage system, blockchain, sup- ply chain ACM CCS: Information systems → Information storage sys- tems 1 Introduction Everything from the clothes on our backs to the food we eat is the end result of a supply chain. Even something as simple as a toothbrush requires the coordination of materi- als, intermediate processes, and distribution before it can be purchased by the consumer in the grocery store. More complex products such as computers or medications rely on similar, if not more complex, supply chains. Figure 1 shows a high level example of a supply chain. The physical product is modifed or transported at each step and even- tually the chain terminates. The information pertaining to the chain, however, is bi-directional and exists more stat- *Corresponding author: Thomas Hepp, University of Konstanz, Information Science Group, D-78464 Konstanz, Germany, e-mail: thomas.hepp@uni-konstanz.de, ORCID: http://orcid.org/0000-0002-7671-0602 Matthew Sharinghousen, University of Konstanz, Distributed Systems Laboratory, D-78464 Konstanz, Germany, e-mail: matthew.sharinghousen@uni-konstanz.de Philip Ehret, Alexander Schoenhals, Bela Gipp, University of Konstanz, Information Science Group, D-78464 Konstanz, Germany, e-mails: philip.ehret@uni-konstanz.de, alexander.schoenhals@uni-konstanz.de, bela.gipp@uni-konstanz.de Figure 1: A high level supply chain from a retail environment show- ing the relationship between the physical product and the informa- tion for each link in the chain. Each link can be further abstracted into its own supply chain [20]. ically. It is this information that needs to be verifed and stored immutably. When considering a long and complex supply chain, how can we be sure of what was performed during each in- termediate step? First approaches are already introduced for tracing products in supply chain cycles, such as [13, 15, 23, 14, 28] Further, if a problem is identifed with the f- nal product, how can we efectively determine which link in the chain produced the problem? Finally, once we have answers to these questions, how can we be sure that the information is correct? To answer this question, the fol- lowing criteria need to be fulflled: All parties in the chain can trust the information, there is no opportunity to make unauthorized modifcations, and the information is avail- able to all authorized parties. This essentially describes a blockchain. There are several problems, however, with using a blockchain to maintain the integrity of and store sup- ply chain information. First, a blockchain technology may have a limit to the amount of data that can be stored in a single block. Second, the cost of committing a transaction to a block may be prohibitively expensive. Third, it may be necessary to share information for computation or verif- cation, but the data itself is confdential or should not be readable by all parties in the chain. The remainder of this paper examines a selection of available technologies in order to gain an overview of which features are currently available, and discuss how these features can be applied to supply chains to answer the open questions from above. Section 2 outlines how the Brought to you by | Stockholm University Library Authenticated Download Date | 12/10/18 1:40 PM