  In the industry, blockchains are increasingly used as the backbone of product
and process traceability. Blockchain-based traceability participates in the
demonstration of product and/or process compliance with existing safety
standards or quality criteria. In this perspective, services and applications
built on top of blockchains are business-critical applications, because an
intended failure or corruption of the system can lead to an important
reputation loss regarding the products or the processes involved. The
development of a blockchain-based business-critical application must be then
conducted carefully, requiring a thorough justification of its dependability
and security. To this end, this paper encourages an engineering perspective
rooted in well-understood tools and concepts borrowed from the engineering of
safety-critical systems. Concretely, we use a justification framework, called
CAE (Claim, Argument, Evidence), by following an approach based on assurance
cases, in order to provide convincing arguments that a business-critical
blockchain-based application is dependable and secure. The application of this
approach is sketched with a case study based on the blockchain HYPERLEDGER
FABRIC.
