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Computer Science editorial

Open AccessOA2026

Blockchain-Enabled Secure Logging for Fiscal Electronic Mechanisms: Evaluation of the Greek eSEND and myDATA Tax Systems

A comparative analysis of hardware-based fiscal devices and software-based e-invoicing platforms reveals critical gaps in transaction integrity guarantees.
Panagiotis Mavridis; Anargyros Baklezos; Christos Nikolopoulos· 2026· DOI 10.48550/arXiv.2609.04356

The core problem

The digitalization of tax systems has introduced new challenges for ensuring the integrity and immutability of fiscal transactions. In Greece, the Fiscal Electronic Mechanisms (FEMs) and the central tax information system eSEND have incorporated blockchain-based integrity mechanisms to secure transaction logging. This paper analyzes the cryptographic architecture of various fiscal devices, including Electronic Cash Registers, Fiscal Printers, Fiscal Signing Machines, and FEMAS devices, which utilize double or triple hash-chain structures to guarantee transaction immutability. In contrast, the architecture of Electronic Invoicing Provider Services and the myDATA central platform is examined, revealing an absence of blockchain-based integrity guarantees. The study aims to compare these two approaches and propose improvements for ensuring transaction integrity in digital tax ecosystems.

Innovation

The analysis reveals that hardware-based fiscal mechanisms implement robust cryptographic integrity measures. Fiscal devices such as Electronic Cash Registers, Fiscal Printers, Fiscal Signing Machines, and FEMAS devices employ double or triple hash-chain structures, ensuring that any modification to a transaction would invalidate all subsequent hashes. The transmission protocol to eSEND includes encryption, sequential validation, and blockchain verification, providing end-to-end integrity from the device to the central database. In contrast, the Electronic Invoicing Provider Services and the myDATA platform lack blockchain-based integrity guarantees. Their architecture relies on software-based logging without cryptographic chaining, making them susceptible to undetected tampering and incomplete transaction records. The comparison demonstrates that hardware-based fiscal mechanisms provide stronger guarantees for transaction completeness and tamper resistance than purely software-based invoicing infrastructures.
The digitalization of tax systems has introduced new challenges for ensuring the integrity and immutability of fiscal transactions. In Greece, the Fiscal Electronic Mechanisms (FEMs) and the central tax information system eSEND have incorporated blockchain-based integrity mechanisms to secure transaction logging. This paper analyzes the cryptographic architecture of various fiscal devices, including Electronic Cash Registers, Fiscal Printers, Fiscal Signing Machines, and FEMAS devices, which utilize double or triple hash-chain structures to guarantee transaction immutability. In contrast, the architecture of Electronic Invoicing Provider Services and the myDATA central platform is examined, revealing an absence of blockchain-based integrity guarantees. The study aims to compare these two approaches and propose improvements for ensuring transaction integrity in digital tax ecosystems.
The study employs a comparative architectural analysis of two distinct fiscal transaction systems: the hardware-based FEMs with eSEND, and the software-based Electronic Invoicing Provider Services with myDATA. The cryptographic mechanisms of fiscal devices are examined, focusing on the implementation of hash-chain structures. For a sequence of transactions , each device computes a hash chain where the hash of transaction incorporates the hash of the previous transaction:

Why it matters

The findings highlight a significant architectural disparity between the two systems. The hash-chain structures in FEMs create a tamper-evident log where any alteration is detectable through hash verification. The blockchain verification at eSEND further anchors the integrity of the entire chain. However, the software-based myDATA platform lacks such mechanisms, relying instead on the trustworthiness of the invoicing providers. This creates a vulnerability where transactions could be altered or omitted without detection. The study proposes improvements for the e-invoicing framework, including the integration of hash-chain logging and blockchain-based verification. A potential architecture for an enhanced myDATA platform could involve a distributed ledger where each invoice is recorded as a transaction, as illustrated in the following Mermaid diagram:

Such improvements would align the software-based system with the security guarantees of hardware-based FEMs, ensuring transaction integrity in digital tax ecosystems.

Who should read this

CS practitioners and researchers

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