ABSTRACT
A novel, trusted, and secure durable medium electronic service is proposed in the paper. The proposed idea joins cryptographic methods (such as signing with an electronic seal and data encryption) with blockchain techniques. The e-service and blockchain databases were implemented on the TTP side, which made the presented concept trusted and secure. The proposed electronic service was oriented towards practical implementations, and it has commonly been developed together with a company from the cybersecurity field (which is considered a TTP in the proposed approach). The concept has been designed to meet the requirements of Polish law (i.e., the conditions and regulations related to the implementation of the durable medium in Poland);nevertheless, it can easily be adapted for other regions. The functionality of the presented e-service is illustrated by the example case study.