Brief Announcement Blockguard: Adaptive Blockchain Security

We change the security of blockchain transactions by varying the size of consensus committees. To improve performance, such committees operate concurrently. We present two algorithms that allow adaptive security by forming concurrent variable size consensus committees on demand. One is based on a single joint blockchain, the other is based on separate sharded blockchains. For in-committee consensus, we implement synchronous Byzantine fault tolerance algorithm (BFT), asynchronous BFT and proof-of-work consensus. We evaluate the performance of our adaptive security algorithms.