(1) Background: Large eHealth systems should have a mechanism to detect unauthorized changes in patients’ medical documentation, access permissions, and logs. This is due to the fact that modern eHealth systems are connected with many healthcare providers and sites. (2) Methods: Design-science methodology was used to create an integrity-protection service model based on blockchain technology. Based on the problem of transactional transparency, requirements were specified and a model was designed. After that, the model’s security and performance were evaluated. (3) Results: a blockchain-based eHealth integrity model for ensuring information integrity in eHealth systems that uses a permissioned blockchain with off-chain information storage was created. In contrast to existing solutions, the proposed model allows information removal, which in many countries’ eHealth systems is a legal requirement, and is based on a blockchain using the Practical Byzantine Fault Tolerant algorithm. (4) Conclusion: A blockchain can be used to store medical data or only security-related data. In the proposed model, a blockchain is mainly used to implement a data-integrity service. This service can be implemented using other mechanisms, but a blockchain provides a solution that does not require trusted third parties, works in a distributed eHealth environment, and supports document removal.

The protection of sensitive information is very important, but also a difficult task. It usually requires a centralised access policy management and control system. However, such solution is often not acceptable in the era of users’ mobility. In the paper we propose a certificate-based group-oriented encryption scheme with an effective secret sharing scheme based on general access structure. The special design of the scheme ensures that the shared secret (encryption key information), a collection of shareholders, and the access structure can be dynamically changed without the need to update the long-term keys and shares owned by shareholders. It is also possible to delegate the access rights to another member of the qualified subgroup or to a new entity from outside the current access structure.

Certificate-based encryption (CBE) combines traditional public-key encryption and certificateless encryption. However, it does suffer to the Denial of Decryption (DoD) attack called by Liu and Au. To capture this attack, they introduced a new paradigm called self-generated-certificate public key cryptography. In this paper we show that the problem of DoD attack can be solved with a new implicit and explicit certificates-based public key cryptography paradigm. More importantly, we propose a concrete implicit and explicit certificate-based encryption (IE-CBE) scheme that defends against DoD attack. This new scheme is enhanced version of CBE scheme and preserves all its advantages, i.e., every user is given by the trusted authority an implicit certificate as a part of a private key and generates his own secret key and corresponding public key. In addition, in the IE-CBE scheme trusted authority has to generate an explicit certificate for a user with some identity and a public key. We prove that our scheme is IND-CCA2⁻ and DoD-Free secure in the random oracle model as hard is to solve p-BDHI and k-CCA problems.

Group encryption schemes based on general access structures can be used to build advanced IT systems, which store and manage confidential documents. The paper proposes a reference architecture of public key cryptography infrastructure required to implement CIBE-GAS scheme. The CIBE-GAS scheme is a certificate-based group-oriented encryption scheme with an effective secret sharing scheme based on general access structure and bilinear pairings. The security architecture required to implement the scheme must be compliant with common standards and technical specifications, e.g. X.509 certificate format and XML-encryption standard for messages. In order to encrypt arbitrary-length messages, we also suggest a new CIBE-GAS-H scheme with a key encapsulation mechanism based on the techniques of Bentahar et al., and combined with one-time symmetric-key encryption.