RadChain: Integration of Radio Frequency and Blockchain Technologies for Secure Document Validation

Document validation and authenticity remain critical challenges due to the risk of fraud and the need for secure and trustworthy processes. This paper presents RadChain, a system that links physical documents to a blockchain record through radio-frequency tags. The proof of concept implements the Near-Field Communication (NFC) pathway; other Radio-Frequency Identification (RFID) tags that can provide the same URL or hash are supported by design but were not tested. RadChain places a lightweight edge service close to the user, with the intended benefit of reducing latency and load on the blockchain node, and uses Alastria, a hybrid public–private blockchain platform, to balance security, privacy and transparency. Each physical document carries an NFC tag storing a URL that embeds the SHA-256 hash of the document, which can be certified, signed and queried against a smart contract through a decentralized application. A successful verification shows that the hash was registered, and by which accounts and when; whether those accounts are trusted is decided by an explicit on-chain authorization registry plus the verifier’s policy, and the check relies on the assumption that the tag is securely bound to the physical document, since retrieving a registered hash does not verify the current printed content. A functional evaluation on the Alastria network covers valid, modified, unregistered and duplicate-operation cases and reports preliminary measurements of the edge service on a Raspberry Pi 4 and a Raspberry Pi 5 (a registered-hash verification takes a median of 28 and 14.5 ms, respectively, measured on the device with a localhost client and therefore excluding the smartphone-to-device hop) and of the blockchain operations. The results show that combining NFC tags with blockchain provides a practical mechanism to trace documents and check the registration of their hash, which may help reduce document fraud in sectors that demand high levels of security, such as the legal system.