  Sharding has emerged as one of the common techniques to address the
scalability problems of blockchain systems. To this end, various sharding
techniques for blockchain systems have been proposed in the literature. When
sharded blockchains process personal data, the data controllers and the data
processors associated with the sharded blockchains need to be compliant with
the General Data Protection Regulation (GDPR). To this end, this article makes
the first attempt to address the following key question: to what extent the
existing techniques developed by different communities such as the distributed
computing community, the distributed systems community, the database community,
identity and access control community and the dependability community can be
used by the data controllers and data processors for complying with the GDPR
requirements of data subject rights in sharded blockchains? As part of
answering this question, this article argues that there is a need for
cross-disciplinary research towards finding optimal solutions for implementing
the data subject rights in sharded blockchains.
