  The constantly growing size of blockchains becomes a challenge with the
increasing usage. Especially the storage of unwanted data in a blockchain is an
issue, because it cannot be removed naturally. In order to counteract this
problem, we present the first concept for the selective deletion of single
entries in a blockchain. For this purpose, the general consensus algorithm is
extended by the functionality of regularly creating summary blocks. Previous
data of the chain are summarized and stored again in a new block, leaving out
unwanted information. With a shifting marker of the Genesis Block, data can be
deleted from the beginning of a blockchain. In this way, the technology of the
blockchain becomes fully transactional. The concept is independent of a
specific block structure, network structure, or consensus algorithm. Moreover,
this functionality can be adapted to current blockchains to solve multiple
problems related to scalability. This approach enables the transfer of
blockchain technology to further fields of application, among others in the
area of Industry 4.0 and Product Life-cycle Management.
