Andrea Tesei, Domenico Lattuca, Alexandr Tardo, Luca Di Mauro · 8 authors
Major maritime carriers are globally demanding improvements in the efficiency of port operations. Cargo carried by ships must be loaded and unloaded quickly with minimal stopover time in the port. This requirement mandates seaports to deploy cutting-edge technology to the port area so that logistic processes are increasingly efficient and reliable. In this scenario, the attack surface of such critical infrastructure is growing very rapidly and advanced security techniques must be deployed to enforce a high attack resilience. A Distributed Ledger-based Credential Management System exploiting a Distributed Ledger Technology (DLT) to enable transparent and real-time tracking of logistic vehicles and cargos within a terminal is presented in this paper. Based on a customization of Vehicular Ad-Hoc Network (VANET) security standards, the proposed scheme provides authentication, authorization, and revocation capabilities to promptly exclude misbehaving logistic vehicles from the system, while maintaining an immutable record of all the logistic vehicles' activity. The laboratory validation demonstrates that the delay of the devised scheme is not dependent on the quay area capacity, thus being applicable in seaports of any size. Furthermore, the effectiveness of the solution is demonstrated with the field trial results obtained with the EU Horizon 2020 COREALIS project testbed deployed in the Port of Livorno.
The articles in this special section focus on distributed ledger technologies (DLT). DLT, of which blockchain is a popular example, are increasingly becoming a popular means to maintain transactional integrity and achieve consensus among competing parties in many modern distributed data exchanges. Indeed, a Gartner survey estimates that by 2020, DLT and blockchain will support the global movement and tracking of $2 trillion of goods and services annually. Unlike centralized files and databases, distributed ledgers rely on peering nodes to record, share, and synchronize transactions and data in their individually maintained local ledgers. In the case of blockchain, information is organized into blocks that are securely and transparently chained together. These blocks become immutable global knowledge among all peers using consensus algorithms to achieve data synchronization. The “append-only, globally accepted” transactions supported by blockchain technologies have given rise to both opportunities and challenges compared to traditional data storage systems. One of the challenges faced by current information sharing systems, and a key concept that makes DLT appealing is the support for the creation of large scale systems from nodes and components that do not trust each other. Being able to reach consensus and share a commonly verifiable ledger is a very powerful primitive, which is already being considered for data sharing applications in energy, pharmaceuticals, and many other domains.
Lăcrămioara Aştefănoaei, Pierre Chambart, Antonella Del Pozzo, Thibault Rieutord · 6 authors
First-generation blockchains provide probabilistic finality: a block can be revoked, albeit the probability decreases as the block "sinks" deeper into the chain. Recent proposals revisited committee-based BFT consensus to provide deterministic finality: as soon as a block is validated, it is never revoked. A distinguishing characteristic of these second-generation blockchains over classical BFT protocols is that committees change over time as the participation and the blockchain state evolve. In this paper, we push forward in this direction by proposing a formalization of the Dynamic Repeated Consensus problem and by providing generic procedures to solve it in the context of blockchains. Our approach is modular in that one can plug in different synchronizers and single-shot consensus. To offer a complete solution, we provide a concrete instantiation, called {{Tenderbake}}, and present a blockchain synchronizer and a single-shot consensus algorithm, working in a Byzantine and partially synchronous system model with eventually synchronous clocks. In contrast to recent proposals, our methodology is driven by the need to bound the message buffers. This is essential in preventing spamming and run-time memory errors. Moreover, {{Tenderbake}} processes can synchronize with each other without exchanging messages, leveraging instead the information stored in the blockchain.
Access control management is an integral part of maintaining the security of an application. Although there has been significant work in the field of cloud access control mechanisms, however, with the advent of Distributed Ledger Technology (DLT), on-chain access control management frameworks hardly exist. Existing access control management mechanisms are tightly coupled with the business logic, resulting in governance issues, non-coherent with existing Identity Management Solutions, low security, and compromised usability. We propose a novel framework to implement dynamic role-based access control for decentralized applications (dApps). The framework allows for managing access control on a dApp, which is completely decoupled from the business application and integrates seamlessly with any dApps. The smart contract architecture allows for the independent management of business logic and execution of access control policies. It also facilitates secure, low cost, and a high degree of flexibility of access control management. The proposed framework promotes decentralized governance of access control policies and efficient smart contract upgrades. We also provide quantitative and qualitative metrics for the efficacy and efficiency of the framework. Any Turing complete smart contract programming language is an excellent fit to implement the framework. We expect this framework to benefit enterprise and non-enterprise dApps and provide greater access control flexibility and effective integration with traditional and state of the art identity management solutions.
Budankailu Kumar Subudhi, Faruk Catal, Nikolay Tcholtchev, Kin Tsun Chiu · 7 authors
VoIP-based emergency communication is a promising approach to improving the safety of citizens worldwide. The transition required in this scope includes substituting the legacy PSTN/SS7 based emergency call system by Next Generation IP based components for call establishment and control. Thereby, SIP is used as a session control protocol and RTP as the means to transfer emergency data between the caller and the corresponding Public Safety Access Point (PSAP). The emergency data is not only restricted to voice communication but can cover a rich variety of data, which can be acquired by different means (including the end-user devices) and transmitted over IP. This includes video, geopositioning data, voice, Real-Time Text, and sensor data in line with emerging IoT architectures and approaches. A vital aspect in this scope is given by the performance of the underlying network, including its capability to establish calls in emergencies and to transfer the data required for serving the situation. Therefore, in this paper, we evaluate the computational performance of the most recent VoIP emergency system implementation, which was developed by the H2020-EMYNOS project as a realisation of the EENA NG112 Long Term Definition (LTD) vision. We perform a series of trials and evaluate the performance of the EMYNOS system in a multi-party lab environment established during the project. We evaluate the time needed to perform basic emergency call operations over IP, whilst in parallel generating Internet type of background traffic. Correspondingly, we worked out a methodology and implemented it in our testbed, both of which are presented in the current paper. The obtained numerical results lead to the conclusion that SIP-based emergency services stand a good chance to replace legacy systems when it comes to their performance. Additionally, we also provide a perspective on how the blockchain technology could potentially be put to use to enhance the quality of the next-generation emergency services. We propose the utilisation of blockchain technology for tracking emergency calls and enabling efficient recognition of fraud calls, which is a critical aspect for PSAP providers concerning the potential denial of service attacks. In this context, we provide evaluations and numerical results based on a private Ethereum based blockchain playground running at the premises of Fraunhofer FOKUS.
We describe MaGPoS, a novel consensus mechanism which is well suited to decentralized blockchain based protocols. MaGPoS is based on a combination of the well known physics of nano-scale magnetism, and previous implementations of proof of stake. This system has been studied by hundreds of thousands of scientists worldwide for over a hundred years, giving it an extreme level of reliability that is needed for a consensus mechanism. We start by explaining the physics, and study the properties that make it particularly beneficial for use in a consensus mechanism. We then show how to apply the physical model to a decentralized network of nodes, each with their own copy of a blockchain. After this, we describe some example calculations that a node in the decentralized network would make, and provide pseudo code for implementation. Finally, we discuss the how the model achieves all of the important properties that one expects of a consensus mechanism.
Abstract Modern distributed data management systems face a new challenge: how can autonomous, mutually distrusting parties cooperate safely and effectively? Addressing this challenge brings up familiar questions from classical distributed systems: how to combine multiple steps into a single atomic action, how to recover from failures, and how to synchronize concurrent access to data. Nevertheless, each of these issues requires rethinking when participants are autonomous and potentially adversarial. We propose the notion of a cross-chain deal , a new way to structure complex distributed computations that manage assets in an adversarial setting. Deals are inspired by classical atomic transactions, but are necessarily different, in important ways, to accommodate the decentralized and untrusting nature of the exchange. We describe novel safety and liveness properties, along with two alternative protocols for implementing cross-chain deals in a system of independent blockchain ledgers. One protocol, based on synchronous communication, is fully decentralized, while the other, based on semi-synchronous communication, requires a globally shared ledger. We also prove that some degree of centralization is required in the semi-synchronous communication model.
The rapid evolution of distributed systems during the 2010s fundamentally altered how software systems were designed, deployed, and operated, particularly in cloud-based and service-oriented environments. As organizations increasingly decomposed monolithic applications into microservices and event-driven components, traditional monitoring approaches centered on host-level metrics and reactive alerting proved insufficient. Failures became probabilistic rather than deterministic, symptoms emerged far from root causes, and system behavior could no longer be fully inferred from static architecture diagrams or predefined dashboards. Within this context, observability emerged not merely as an operational concern but as an engineering discipline that directly influences how systems are designed, instrumented, and evolved over time. Observability driven engineering refers to the practice of designing software systems such that their internal states can be inferred through externally visible signals under real-world operating conditions. By 2019, this concept had gained traction across distributed systems research and industry practice, informed by earlier control theory definitions and reinforced by practical challenges in debugging production microservices. Rather than treating telemetry as an afterthought added during operations, observability driven engineering integrates metrics, logs, and distributed traces into the development lifecycle itself, shaping interface contracts, failure semantics, and deployment strategies. This shift reflects a recognition that correctness, reliability, and performance in complex systems cannot be validated solely through pre-production testing. In regulated domains such as financial services, the need for observability carries additional significance. Payment processing systems, fraud detection pipelines, and ledger services operate under strict latency, consistency, and auditability requirements, while simultaneously being subject to partial failures, traffic bursts, and external dependencies. In such environments, the inability to explain system behavior during anomalies is not merely an inconvenience but a material operational and regulatory risk. Observability driven engineering therefore intersects with compliance obligations, incident response processes, and risk management practices, extending its relevance beyond purely technical concerns. This paper examines observability driven engineering as understood and practiced by May 2019, situating it within the broader evolution of software architecture from monolithic systems to distributed, cloud-native platforms. It synthesizes academic literature and industry experience to articulate a conceptual model for observability-aware system design, emphasizing the relationship between instrumentation, architectural layering, and operational feedback loops.
Elie Kfoury, Jose Gomez, Jorge Crichigno, Elias Bou‐Harb · 5 authors
Network Address Translation (NAT) is a method that enables devices with private IP addresses to connect to the Internet by sharing a public IP address. Traversing the NAT device remains a challenge for a wide range of applications such as Voice over IP (VoIP) and Internet of Things (IoT). The Port Control Protocol (PCP) is a relatively new protocol standardized by the Internet Engineering Task Force (IETF) to solve the NAT traversal issues. It allows a NATed device to request and manage a mapping between its private IP address and transport-layer port to a public IP address and port. As PCP requires an application-dependent method for distributing the mappings to remote hosts, several attacks can target the distributing server and render the communication channel vulnerable. In this paper, we propose and implement a decentralized Blockchain-based approach for distributing PCP-mappings, enabling secure end-to-end (e2e) direct communications without any trusted third party server. NATed devices register their PCP mappings and public keys into the Blockchain, and other peers can then learn about these mappings to establish end-to-end secure direct communications. The implementation verifies that the system is feasible in terms of transactions fees, can simplify and secure end-to-end direct communications, and can interwork with conventional security methods.
In this paper, we describe LUNES-Blockchain, an agent-based simulator of blockchains that is able to exploit Parallel and Distributed Simulation (PADS) techniques to offer a high level of scalability. To assess the preliminary implementation of our simulator, we provide a simplified modelling of the Bitcoin protocol and we study the effect of a security attack on the consensus protocol in which a set of malicious nodes implements a filtering denial of service (i.e. Sybil Attack). The results confirm the viability of the agent-based modelling of blockchains implemented by means of PADS.
Centralized network solution have been around for a long time, despite having a considerable issue of trust, in which users need to rely on the implementation of the system. During unfortunate incidents such as centralized server hacking attacks, users' data can be stolen and distorted, as well as not available while requested. Blockchain is discovered and believed to be a distributed network solution which can mitigate the above issue. \n \nThis bachelor's thesis studies how blockchain network can be integrated into a social financial mobile application. The research is completed by developing a smart contract and connect it with the mobile application. The smart contract is written in the Solidity programming language and run on the Ethereum network.
Konstantnim povećanjem postotka ljudske populacije u gradovima povećava se i broj automobila u gradovima. S povećanjem broja automobila dolazi do većeg opterećenja prometa te zahtjeva za novim parkirnim mjestima. Kako bi smanjilo opterećenje prometnica i potražnja za parkirnim mjestima potrebno je osmišljavati nove metode. Jedna od tih metoda je i dijeljenje automobila kojoj je cilj smanjiti vrijeme koje vozilo provode na parkirnom mjestu. Za implementaciju takve metode potrebno je kreirati sustav koji će omogućivati iznajmljivanje i dijeljenje automobila te plaćanje usluge. U ovome radu izraditi će se dio aplikacije za dijeljenje automobila koja će funkcionirati na pametnom ugovoru unutar blockchain-a odnosno distribuiranog zapisnika. Postupak izrade te funkcionalnosti aplikacije objašnjene su unutar rada. Aplikacija se fokusira na plaćanje koristeći pametne ugovore te su opisani ostali dijelovi sustava potrebni za implementaciju aplikacije koje nisu unutar okvira ovoga rada.
Stefano Angieri, Alberto García-Martínez, Bingyang Liu, Zhiwei Yan · 6 authors
The current system to manage the global pool of IP addresses is centralized\nin five transnational organizations, the Regional Internet Registries (RIRs).\nEach of these RIRs manage the address pool for a large number of countries.\nBecause the RIRs are private organizations, they are subject to the legal\nframework of the country where they are based. This configuration results in a\njurisdictional overflow from the legal framework of the countries where the RIR\nis based to all the countries that the RIRs are serving (the countries served\nby the RIRs de facto become subjects of the legal system of the country where\nthe RIR is hosted). The situation is aggravated by the deployment of new\nsecurity techniques such as the RPKI and BGPsec, that enable enforcement of\nallocations by the RIRs. In this paper we present InBlock, a blockchain-based\ndistributed governance body aimed to provide de-centralized management of IP\naddresses. InBlock also aims to fulfil the same objectives as the current IP\naddress allocation system, namely, uniqueness, fairness, conservation,\naggregation, registration and minimized overhead. InBlock is implemented as a\nDecentralized Autonomous Organization, i.e., as a set of blockchain's smart\ncontracts in Ethereum. Any entity may request an allocation of addresses to the\nInBlock registry by solely performing a (crypto)currency transfer to the\nInBlock. The fee required, along with the annual renewal fee, serves as a\nmechanism to deter stockpiling and other wasteful practices. As with any novel\ntechnology, there are many open questions about the usage of blockchains to\nbuild an IP address registry. For this reason, we believe that practical\nexperimentation is required in order to have hands-on experiences about such a\nsystem. We propose to conduct an experiment on distributed address management\nusing InBlock as a starting point to inform future directions in this area.\n
La aparición de las tecnologías Blockchain/Distributed Ledger está significando una revolución en los paradigmas de Internet. En el presente proyecto, se ha aplicado HyperLedger Fabric, una tecnología de Distributed Ledger permisionado y privado, en un escenario entre varias empresas.
To effectively participate in modern collaborations, member organizations should be able to share digital resources with various partners, while ensuring their digital resources are protected from inappropriate access.In the existing literature, a substantial amount of research on centralized access control in the context of a single organization has been carried out.However, research on decentralized access control in a collaborative environment is scarce.To advance research in this area, I implemented a prototype of a decentralized access control system, which supports transparency, auditability, immutability, and equality in a collaboration environment, using the Multichain blockchain platform, RESTful web services, and Java programming language.The prototype was developed to evaluate two primary metrics: average response time and throughput.To achieve this, I carried out a number of experiments to measure both metrics on a Local Area Network (LAN) and on Amazon Web Services (AWS) under 84 different experimental conditions.The LAN setup provides a baseline for system performance under optimal conditions, while the cloud infrastructure represents a real-world use case.With low-system loads (comprising one to thirty concurrent clients and a single server running the system), the LAN setup outperformed the AWS setup by a factor of 2.5 based on throughput.On the other hand, when the system load is significantly increased, with more servers running the system, the AWS and LAN setups showed only a marginal difference in their performance.This demonstrates the potential to horizontally scale the decentralized access control system using blockchain on cloud infrastructure.
Purwono Purwono, Alfian Ma’arif, Wahyu Rahmaniar, Qazi Mazhar ul Haq · 6 authors
Blockchain technology has a promising future in a number of industries and enterprises. Formerly connected to virtual currency like Bitcoin, blockchain has evolved into a versatile technology with many applications. In the upcoming years, it is predicted that blockchain will revolutionize a variety of industries, including banking, supply chain management, healthcare, voting systems, and more. The future of blockchain technology depends critically on its ability to increase security and transparency. By providing a decentralized and unchangeable record, eliminating the need for middlemen, and boosting participant confidence, blockchain promotes secure and traceable transactions. This transparency has the potential to transform whole industries by reducing fraud, streamlining processes, and increasing output. Blockchain also has the power to change financial systems. Blockchain-based smart contracts facilitate faster, more efficient transactions by automating and enforcing contractual agreements without the need for middlemen. By enabling speedier cross-border transactions, reducing costs, and boosting financial inclusion, tokenization and blockchain-based digital currencies have the potential to overturn conventional banking institutions. Blockchain’s key attributes, including decentralization, transparency, immutability, and security, make it a desirable choice for a range of organizations. Cross-border payments, trade finance, and smart contracts are just a few of the financial sector processes that blockchain technology has the potential to enhance and automate, lowering costs and increasing productivity. Additionally, the tamper-resistance of blockchain technology can boost transaction security and reliability, allowing for a wider use in traditional financial institutions. Outside of the financial industry, blockchain technology has a lot of promise, particularly in industries like supply chain management, healthcare, energy, intellectual property, and governance. By enabling transparent and traceable transactions, blockchain may improve supply chain efficiency, ensure product authenticity, and boost customer trust. By facilitating the secure exchange of patient data and research data, the decentralized nature of blockchain technology can enhance data security, interoperability, and privacy in the healthcare sector. A more decentralized and sustainable energy ecosystem may be supported by blockchain technology through peer-to-peer energy exchange, grid management, and monitoring of renewable energy certificates in the energy sector. Additionally, blockchain technology has the potential to transform decentralized governance structures, voting procedures, intellectual property rights, and digital identity management. By allowing people to own and manage their digital identities, blockchain can enhance privacy and reduce identity theft. Blockchain-based voting systems can offer transparency, security, and verifiability, thereby increasing voter turnout and public trust in democratic institutions. Blockchain can also enable the secure and transparent management of intellectual property rights, fostering author credit and just compensation.
Distributed ledger technology, a method of storing and maintaining the integrity of multiple copies of critical data using a massively redundant network of participating machines, has found a “killer application” in blockchain, a type of distributed ledger. A blockchain consists of sequential blocks that may never be modified or reordered, leaving a public, auditable record that is consistent and highly resistant to tampering and deletion. These qualities make blockchain eminently suitable for its most common use, cryptocurrency, and its occasional variants in the form of cryptocurrency tokens, used to represent ownership or some other right to virtual or physical goods and capabilities. Blockchain also enables smart contracts, discrete bodies of software written to serve both as the memorial and the means of execution of an agreement between parties. Smart contracts can have all the elements of a traditional contract, and as jurisdictions legislate or jurists rule on the fine points of enforceability and the acceptability of smart contracts as traditional contracts, applications in nearly every area of commerce have emerged. Digital lawyers may not need to become software developers, but deepening their understanding of the capabilities and limitations of the technology, developing a keen awareness of the issues at the intersection between code and the law, as well as the law’s readiness in this area, will be of great advantage to them and their clients in this rapidly evolving area at the intersection of technology, commerce and law.
Die Möglichkeit der Programmierbarkeit des Bitcoins ist fast ein nachträglicher Einfall, auch wenn Sidechain‐Vorschläge diese Programmierbarkeit ein wenig leichter machen wollen und es bereits Altcoins mit verschiedenen spezifischen Anwendungen gibt. Im Gegensatz dazu wurde das Kryptowährungstechnologieprojekt Ethereum von Vitalik Buterin, seinem Erfinder, von Tag 1 als Software‐Entwicklungsplattform für dezentrale Applikationen konzipiert, und ihre Blockchain wurde speziell entwickelt, um die Ausführung dieser dezentralen Apps (auch Dapps genannt) zu unterstützen. Vitalik Buterin, 1994 in Russland geboren, war vor der Gründung von Ethereum auch involviert in die Entwicklungsprojekte Colored Coins und Mastercoins. Er gewann 2014 den "World Technology Award" und ein Stipendium des Risikokapitalgebers Peter Thiel. In dem Diskussionspapier zu Ethereum skizzierte Buterin vor allem die Grenzen einer Programmierbarkeit der Bitcoin‐Blockchain und schlug die Erstellung einer neuen komplett programmierbaren Blockchain mit einer turing‐vollständigen Programmiersprache vor. Anders als andere Blockchain‐Projekte soll die Ethereum Software nicht nur für einen Zweck nutzbar sein – sondern soll die Basis für die Erarbeitung aller möglichen Arten von Lösungen sein und dabei die Umsetzung intelligenter Verträge (Smart Contracts) ebenso erfassen als auch die Ethereum‐spezifische Idee von dezentralen autonomen Organisationen (DAOs).
Future factory production and assembly environments require smart automation and are controlled by a massively increasing number of computers with sensorial feedback from machines, parts, products, and humans, consisting of a wide variety of different networked devices and software programs, which can be considered as one big use case of pervasive and cloud computing with vanishing boundaries between the computing and the environment, and with a strong focus on decentralized distributed computing and information storage. These new complex information processing architectures are composed of hierarchical network graphs, and require some kind of self-organization and adaptability to overcome single-point of failure and robustness constraints. The data acquired from machines and sensitive products or parts are growing at a fast rate, leading to a large data volume that must be handled distributed with pre-processing, map- and reduce, and filtering algorithms. Mobile Agents can be deployed in such large-scale and hierarchical network environments crossing barriers transparently, for example, industrial manufacturing and assembly environments, the Internet, Sensor Networks, and Cyber-Physical Systems. The networks can consist of high- and low-resource nodes ranging from generic computers to microchips, and the supported network classes range from body area networks to the Internet including any kind of sensor and ambient network. Mobile Agents can perform distributed computation in an autonomous manner.In this work Agents are represented by mobile program code that can be modified at run-time by the Agents themselves. The presented approach enables the development of sensor clouds and smart systems of the future integrated in daily use computing environments and the Internet. Agents can migrate between different hardware and software platforms by migrating the program code of the agent, which embeds the control state and the private data of an agent, finally encapsulated in self-initializing and self-containing code frames.This cross-platform interoperability is ensured by a modular and scalable Agent Processing Platform. The entire information exchange and co-ordination of Agents with other Agents and the environment is performed by using a Tuple Space database, unifying the platform and architecture specific data representation. The Tuple Space is used for any kind of information exchange including program code and directory and file system services mapped on the Tuple Space. Beside architecture specific hardware and software implementations of the agent processing platform, there is a JavaScript (JS) implementation layered on the top of a distributed co-ordination and management layer including distributed file and name services. The JS platform enables the integration of Multi-Agent Systems (MAS) in Internet server and application environments (e.g., WEB browser). Agents can migrate transparently between different classes of computing devices and environments, ranging from hardware-level sensor networks (embedded in technical structures) to WEB browser applications or network servers without any required transformation.
The notion of Multi-Agent System (MAS) environment, as remarked by recent literature, has gained a key role, becoming a mediating entity, functioning as enabler but possibly also as a manager and constrainer of agent actions, perceptions, and interactions 1 while addressing the requirements of openness and scalability. According to such a perspective, the environment is not a merely passive source of agent perceptions and target of agent actions which is, actually, the dominant perspective in agency, but a first-class abstraction that can be suitably designed to encapsulate some fundamental functionalities and services, such as coordination and organization, besides agent mobility, communications, security, etc [2]. Then, the environment dimension appears to intersect with all the dimensions that should be addressed to define an agreement between autonomous agents, that is, all the different Agreement Technologies giving support to the building, development and management of agreements in decentralized and open systems between autonomous agents. Those dimensions are the ones related to the development of technologies dealing with: Semantics, Norms, Organizations, Argumentation & Negotiation, and Trust.
Autonomous Decentralized System (ADS) has been making progress in these 31 years since it was proposed in 1977. During these long years in the rapidly advancing computer and communication technologies, the ADS concept has not been changed but its technologies have been growing in accordance with the change and diversity of the social, economical and personal requirements and through the globalization of the market and the restructuring organizations. The ADS technologies are system-atized to cover all processes of system design, operation, maintenance and modification. This paper reviews the work done in fields of ADS in past 31 years from not only technological perspectives, but it also encompasses users requirements and value, system design, industrial activity, academic activity and standardization [1]-[26]. Moreover the new directions of the ADS are suggested.
The recent developments in the mobile technology (mobile phones, middleware) created a need for new methods of protecting the code transmitted through the network. The proposed mechanisms not only secure the compiled program, but also the data, that can be gathered during its "journey". The oldest and the simplest methods are more concentrated on integrity of the code itself and on the detection of unauthorized manipulation. Other, more advanced proposals protect not only the code but also the execution state and the collected data. The paper is divided into two parts. The first one is mostly devoted to different methods of securing the code and protecting its integrity; starting from watermarking and fingerprinting, up to methods designed specially for mobile agent systems: encrypted function, cryptographic traces, time limited black-box security, chained-MAC protocol, publicly-verifiable chained digital signatures The second part presents new concept for providing mobile agents with integrity protection, based on a zero-knowledge proof system.