Design of Anonymous Endorsement System in Hyperledger Fabric
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Permissioned Blockchain has become quite popular with enterprises forming consortium since it prioritizes trust over privacy. One of the popular platforms for distributed ledger solution, Hyperledger Fabric, requires a transaction to be endorsed or approved by a group known as endorsers as per the specifications in the endorsement policy. To endorse a transaction, an endorser mentions its identity along with the signature so that it can be verified. However, for certain transactions, difference in opinion may exist among endorsers. Disclosure of identity of endorser may lead to conflict within the consortium. In such cases, an endorsement policy which allows an endorser to support a transaction discreetly but simultaneously takes into account the decision of the majority is preferred. As a solution, we propose an Anonymous Endorsement System which uses a threshold endorsement policy. For hiding the identity of endorsers, a new ring signature scheme, called Fabric's Constant-Sized Linkable Ring Signature (FCsLRS) with Transaction-Oriented linkability has been proposed. We have implemented the signature scheme in Golang and analyzed its security and performance by varying the RSA modulus size. Feasibility of implementation is supported by experimental analysis. Signature generation and verification is quite fast, with execution time remaining constant irrespective of change in message length or endorsement set size for a given RSA modulus value. Lastly, we also discuss the integration of the scheme on v1.2 Hyperledger Fabric.
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