Secure Scheme Against Compromised Hash in Proof-of-Work Blockchain
Blockchain is built on the basis of peer-to-peer network, cryptography and consensus mechanism over a distributed environment. The underlying cryptography in blockchain, such as hash algorithm and digital signature scheme, is used to guarantee the security of blockchain. However, past experience showed that cryptographic primitives do not last forever along with increasing computational power and advanced cryptanalysis. Therefore, it is crucial to investigate the issue that the underlying cryptography in blockchain is compromised.
This paper aims at the challenge that the underlying hash algorithm is compromised in blockchain. In 2017, M. Sato et al. firstly addressed the issue by proposing a framework of transition approach from the compromised hash algorithm to a secure one. Nevertheless, this approach is actually a hardfork if it is applied to proof-of-work blockchain, which is much likely to cause disagreement of the blockchain community and should be avoided accordingly. To fill this gap, we propose a softfork transition scheme to deal with the challenge that compromised hash brings into proof-of-work blockchain. Our scheme provides a secure transition in the case of compromised hash, keeping the validity of past data in the blockchain as well. We also show that a proof-of-work blockchain with our scheme is much more secure than the original one (i.e. without our scheme).
KeywordsBlockchain Compromised hash Softfork transition scheme Proof of work
We would like to thank the anonymous reviewers for their helpful feedback. The authors are supported by the National Natural Science Foundation of China (Grant No. 61672347, 61572318, 61672339).
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