  A blockchain is redactable if a private key holder (e.g. a central authority)
can change any single block without violating integrity of the whole
blockchain, but no other party can do that. In this paper, we offer a simple
method of constructing redactable blockchains inspired by the ideas underlying
the well-known RSA encryption scheme. Notably, our method can be used in
conjunction with any reasonable hash function that is used to build a
blockchain. Public immutability of a blockchain in our construction is based on
the computational hardness of the RSA problem and not on properties of the
underlying hash function. Corruption resistance is based on the computational
hardness of the discrete logarithm problem.
