Introduction

Modern medicine is undergoing a period of digital transformation, during which blockchain technology is emerging as one of the key catalysts for change, implying further patient involvement in the management of their own medical data and treatment processes [1, 2].

The relevance of this study is due to the growing need for secure, transparent, and patient-controlled systems for managing medical data.

Successful implementation of blockchain technologies in healthcare requires a multi-level personnel training system, integrating theoretical foundations with practical skills. Healthcare professionals need to understand the principles of blockchain architecture, cryptographic methods of data protection, consensus algorithms, and their applicability in medical systems. Special attention should be paid to the study of consortium blockchains as the most promising model for healthcare.

Traditional centralized data storage systems are vulnerable to cyberattacks, unauthorized access, and information falsification.

Blockchain is a distributed system for recording transactions, where each block contains cryptographically linked information with previous blocks, ensuring data immutability [3]. Although blockchain technology gained the most fame as the fundamental platform for cryptocurrencies like Bitcoin, equating these concepts is incorrect. Blockchain is a more general technology whose application potential significantly exceeds the financial sphere. In healthcare, in particular, this technology opens up possibilities for creating immutable, decentralized, cryptographically protected, and chronologically verifiable registries for the permanent storage of medical documentation, including medical reports, extracts, and prescriptions [1, 2].

Objective of this article is to analyze existing and promising patient-oriented applications of blockchain in medicine, identify key technological and organizational challenges, and outline directions for further research.

Materials and methods

The choice of technological solution based on the degree of openness is decisive when selecting a platform. The choice of a specific platform type is determined by system characteristics such as the level of confidentiality, performance, governance model, and degree of decentralization.

Three main types of blockchain networks are distinguished: public, private, and consortium (federated).

Public blockchains, or permissionless blockchains, are fully open and decentralized networks. Anyone can join the network, participate in the consensus process, read data, and send transactions for inclusion in the ledger [4].

Due to their transparency and low throughput, public blockchains in their pure form are poorly suited for storing medical data. For instance, the Bitcoin network processes 5-7 transactions per second and has a block formation time of about 10 minutes; Ethereum processes 20-25 transactions per second, forming a block in 5-6 minutes, which is completely insufficient on a national scale, currently handling millions of transactions per day. However, they can be used for public verification and immutable timestamping of hashes of medical documents stored off-chain, thereby confirming their integrity and creation time without disclosing the actual content [5-7].

Private blockchains, or permissioned blockchains, are managed by a single organization, where the central authority determines who can join the network, view data, and perform transactions. This type is optimal for internal processes of large medical organizations. It can be used to create a secure internal repository and manage access to electronic medical records (EMRs) within an institution [5-7].

Consortium or federated blockchains represent a hybrid model, governed by a group of pre-defined organizations rather than a single entity or an undefined circle of entities. This model is also permissioned, but decentralization is achieved at the consortium level. This model appears, in our view, to be the most promising for most medical applications. Due to the balance between decentralization and control, it will allow the creation of secure networks for data exchange between various participants in the healthcare system, regional and federal centers, laboratories, insurance companies, research institutes, and regulatory bodies. This ensures interoperability while maintaining strict control over access and data confidentiality [5-7].

Table. Comparison of blockchain platforms

CharacteristicPublic BlockchainPrivate BlockchainConsortium BlockchainAccess ManagementPermissionlessPermissionedPermissionedParticipantsAnyoneSingle organizationMultiple organizations (consortium)ConsensusDetermined by all participants (e.g., Proof-of-Work)Controlled by network owner (e.g., Proof-of-Authority)Determined by consortium members (e.g., PBFT)Transaction SpeedLowHighHighConfidentialityLow (pseudonymous)HighHigh (within the consortium)Platform ExamplesBitcoin, EthereumHyperledger Sawtooth, Geth (Go Ethereum), Waves EnterpriseHyperledger Fabric, R3 CordaMedical ApplicationsPublic verification, timestampingInternal audit, data management within a single clinicInter-organizational EMR exchange, clinical trials, drug supply chains, etc.

Next-generation electronic medical records

The traditional model of managing electronic medical records (EMRs) is characterized by a centralized architecture with fragmented data distribution across various medical information systems (MIS) in different healthcare institutions, without the possibility of unified access.

Blockchain solutions offer a patient-controlled model where the patient becomes the steward of their data and can selectively grant access to medical professionals. In this model, the blockchain functions as a cryptographically protected registry of access permissions, not as a repository for the medical data itself. Two layers of operation are used [8, 9]:

Storing large volumes of medical data, such as MRI or CT scans, directly on the blockchain is impractical and expensive. A more realistic approach is a hybrid model where the files themselves are stored in a secure distributed storage, while only their hashes and metadata, confirming their integrity and access history, are recorded on the blockchain.

To solve the scalability problem, the use of distributed file systems such as the InterPlanetary File System (IPFS) is necessary. IPFS provides content-addressed file storage using cryptographic hashes, geographically distributed data replication to ensure high availability, and versioning of medical records preserving the complete history of changes [9].

Telemedicine and remote patient monitoring

The potential applications of blockchain are not limited to in-hospital and corporate solutions. The COVID-19 pandemic demonstrated the importance of telemedicine solutions and the need for secure data transfer between patients and medical specialists.

Basic solutions include the integration of IoT devices and wearable sensors for health monitoring. The technology guarantees that this data is recorded in the ledger in an immutable form directly from the device, eliminating the possibility of forgery or accidental distortion, ensuring high reliability of information for clinical decision-making.

Smart contracts are programmable algorithms that automatically execute when predefined conditions are met. In telemedicine, they can be used to automate processes such as processing payments for consultations or sending notifications to a doctor when sensor readings reach critical levels.

During a teleconsultation, a physician can obtain authorized access to a complete and reliable medical history, test results, and data from monitoring devices, regardless of which institution created this data. The patient retains full control over their information, using private keys to grant or revoke access [7, 11]. By flexibly managing access to their data through smart contracts, the patient can grant temporary access to the attending physician for the duration of the consultation or allow a research organization to use anonymized data for scientific purposes. All data access operations are recorded on the blockchain, ensuring complete transparency and accountability [10].

Patient dynamic informed consent management

Traditional informed consent models are static and do not adapt to the changing needs of treatment or research. Blockchain platforms enable the implementation of dynamic consent, where patients, through a digital interface, can manage permissions for the use of their data in a detailed and interactive manner, allowing them to make granular decisions as needed.

To address these challenges, the dynamic consent system METORY, adapted for clinical research, was developed on the Hyperledger Fabric platform [12]. The patient reviews the study materials in an application and then provides an electronic signature; the researcher also signs the form. Each stage of this process is recorded in the ledger as a transaction.

When changes are made to the study protocol, a new version of the consent form is created. The hash value (a unique digital fingerprint) of the document is recorded on the blockchain, guaranteeing that even the slightest change in the document is captured, ensuring data integrity. Participants receive a notification and must sign the updated form [13]. The platform also includes a chat for communication between the participant and the researcher during and after the consent process.

Further development of the informed consent model from dynamic to proactive (predictive) mode is possible: the patient not simply accepts/rejects requests for changes but predefines and formalizes a comprehensive set of rules and conditions under which their medical data may be used in the future, even for purposes not yet formulated at the time of giving consent. The technological basis for implementing the "prosent" concept is the synergy of blockchain technologies and smart contracts. Blockchain provides the necessary trust infrastructure, and smart contracts provide the logic for automation. For example, the ConsentChain platform demonstrates the practical implementation of dynamic consent for clinical-genomic research [13-15].

The challenges of implementing blockchain in medicine

The fundamental characteristic of blockchain—immutability—comes into conflict with one of the data subject's rights enshrined in modern regulatory acts—the "right to be forgotten." In the context of patient-oriented medicine, this requires specialized architectural solutions. For instance, extended use of distributed file systems (IPFS) and storage of appended documents on certified servers of medical organizations, accompanied by the possibility of deleting the cryptographic key, making decryption of the original records practically impossible. At the same time, the blockchain retains an immutable record of the very fact of the data's existence and the transaction that destroyed the access key, providing a complete audit trail while simultaneously guaranteeing the integrity of the interaction history and satisfying the patient's right to be forgotten [16, 17]. It must also be considered that a participant who previously gained access to the decrypted document and has a local copy of it operates beyond the control of the blockchain system.

In conditions where the confidentiality of stored data must be ensured for decades ahead, considering the development of digital technologies (particularly quantum computing, where future attacks could retrospectively decrypt records protected today), the implementation of robust post-quantum encryption is a necessary preventive measure. A transition from current standards, such as elliptic curve cryptography, to lattice-based cryptosystems and other cryptographic methods, such as CRYSTALS-Kyber [18], appears relevant. Lattice-based cryptography, besides cryptographic strength, is compatible with homomorphic encryption, allowing arbitrary computations to be performed directly on encrypted data without decrypting it.

Another constraining factor is the high energy resource consumption for complex computations (such as the Proof-of-Work consensus mechanism, raising environmental concerns). The development of "green" models with low energy consumption is underway, for example, the Proof-of-Stake mechanism, where the right to create a new block is granted to validators proportionally to their stake in the network, reducing computational demands and energy consumption. In the context of medical consortium networks, where participants are known and trusted, energy-efficient algorithms like Proof-of-Authority have become even more widespread [19].

In practical application, existing MIS are based on principles of centralized data management, strict component hierarchy, and synchronous interaction between modules. Most medical institutions in the Russian Federation operate legacy information systems characterized by proprietary data formats and limited capabilities for integration with external systems.

Russia's legal system is still at the stage of adapting to new digital realities. The lack of a clear legislative framework defining the status of medical data in blockchain systems and standards for their use is one of the main obstacles [16]. There is a conflict between the classical legal definition of a document as information recorded on a tangible medium and the decentralized nature of blockchain. In a distributed network, a medical document is not a single file but a logical entity identified by its cryptographic hash, whose replicas and fragments may simultaneously exist on multiple nodes. The information is in a state of constant synchronization and verification, and its medium is the entire network as a whole, not an individual component. The legal focus should shift from physical localization to cryptographic proof of the integrity and provenance of information [5, 16].

Technically, the most interesting implementation for application in the healthcare system of the Russian Federation is the Masterchain platform, built on Hyperledger Fabric and included in the Register of Domestic Software. It supports GOST cryptography algorithms and architectural solutions compliant with Federal Law-152 "On Personal Data." The platform's modular structure, using isolated channels and private data collections, allows for the creation of complex consortium networks.

Conclusion

The presented analysis of the application of blockchain technologies in healthcare demonstrates the promise of transitioning from centralized architectures to patient-oriented models of medical data management. Blockchain will enable a cryptographically protected infrastructure for implementing dynamic patient consent, decentralized management of electronic medical records, and secure data exchange in telemedicine applications.

Scalability and performance remain significant limitations for the widespread adoption of solutions in Russian healthcare. Public blockchains like Bitcoin and Ethereum demonstrate insufficient throughput for processing millions of medical transactions on a national scale. Consortium blockchains, Masterchain, and other platforms based on Hyperledger Fabric represent the optimal solution, providing a balance between decentralization and control with high performance.

In the short term, it is necessary to focus on a hybrid architecture, where medical data and larger files are stored in distributed file systems like IPFS, creating a cost-effective model, while the blockchain ensures the consistency of the distributed ledger, guaranteeing data integrity through cryptographic hashes.

The long-term security of medical data requires a preventive transition to post-quantum cryptographic algorithms. The introduction of lattice-based cryptosystems, such as CRYSTALS-Kyber, will ensure resistance to quantum attacks while maintaining compatibility with homomorphic encryption.

The lack of a clear international and domestic legislative framework defining the status of medical data in blockchain systems slows down the practical implementation of the technology. Standardization of interaction protocols between blockchain platforms and traditional MIS is also necessary.

Further development should concentrate on creating a national consortium network involving federal and regional medical institutions, insurance companies, research organizations, other participants in the healthcare system, and counterparties.

In addition to enhancing control over personal medical information, the introduction of these technologies will increase trust in medical services due to transparency and the possibility of audit.

The successful implementation of blockchain solutions in Russian healthcare requires synchronized development of technological infrastructure, legal framework, and continuous improvement of the competencies of medical professionals in the field of digital technologies. The formation of a new type of medical specialist—cyberneticists who integrate clinical expertise with deep knowledge of information technology—is a task for Russian healthcare, being addressed, among others, at the Yaroslavl State Medical University and other leading medical universities in the country.