MOF-BC: A memory optimized and flexible blockchain for large scale networks

The inherent immutability offered by Blockchains (BC) ensures resilience against modification or removal of the stored data. In large scale networks like the Internet of Things (loT), however, this feature significantly increases BC storage size and raises privacy concerns. In this paper, we propose a Memory Optimized and Flexible BC (MOF-BC) that enables the loT users and service providers to remove or summarize their transactions and age their data and thus exercise their "right to be forgotten". To increase privacy, a user may employ multiple keys for different transactions. However, to facilitate removal of the stored transactions in the future, all keys would need to be stored which complicates key management and storage. MOF-BC introduces the notion of a Generator Verifier (GV) which is a signed hash of a Generator Verifier Secret (GVS). The GV changes for each transaction to provide privacy yet is signed by a unique key, thus minimizing the information that needs to be stored. A flexible transaction fee model and a reward mechanism is proposed to incentivize users to participate in optimizing memory consumption. We propose MOF-BC as a generalized solution, which can be implemented on top of any existing or future BC instantiation. Qualitative security and privacy analysis demonstrates that MOF-BC is resilient against several security attacks. Evaluation results show that MOF-BC decreases BC memory consumption by up to 25% and the cost incurred by users by more than two orders of magnitude compared to conventional BC instantiations. (C) 2018 Elsevier B.V. All rights reserved.