Vidor Gencel, Developer in Belgrade, Serbia
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Vidor Gencel

Verified Expert  in Engineering

Blockchain Developer

Belgrade, Serbia
Toptal Member Since
April 30, 2018

Vidor is a Computer Science Ph.D. candidate actively doing research and development in the blockchain space with a focus on Tendermint, Ethereum, and Hyperledger. He has been involved in software development since a young age and has participated in the development of different software solutions for microprocessors, core banking, the web, and money-handling equipment. Vidor has strong business English and years of remote-working experience.


Amazon Web Services (AWS), Docker, Node.js, Go, JavaScript, Cosmos SDK...
Freelance Work
Node.js, Truffle, Web 3.0, JavaScript, Solidity, Blockchain
Under NDA
Amazon Web Services (AWS), JavaScript, Go,, BigchainDB, Cosmos SDK...




Preferred Environment

Slack, Git, Visual Studio Code (VS Code), MacOS

The most amazing...

...thing I've done is discover critical security vulnerabilities in Ethereum smart contracts that could have produced great financial loss.

Work Experience

Founder | Blockchain Architect

2019 - PRESENT
  • Led development process end-to-end, from proposal development to requirements engineering, architecture, development, and delivery.
  • Defined product development guidelines for cryptocurrency wallets, claim issuance, and aggregation/selective disclosure using advanced cryptographic techniques.
  • Technically vetted and managed a team of 10 engineers and designers.
  • Architected and led the development of an advanced verifiable claim processing system to optimize fundraising processes on crypto exchanges by aggregation and selective disclosure of cryptographic claims.
  • Architected solutions based on Tendermint and Cosmos SDK.
  • Architected and participated in the development of a Quorum based blockchain used to manage reward points. Apart from the core blockchain and smart contract development, the system included a web wallet interface, an administration panel, a blockchain explorer, and a system monitoring dashboard.
  • Architected and participated in the development of a dashboard that aggregates blockchain data and displays proof of stake related economic metrics.
Technologies: Amazon Web Services (AWS), Docker, Node.js, Go, JavaScript, Cosmos SDK, Tendermint, Hyperledger, Quorum, Ethereum, Cryptography, Solution Architecture

Blockchain Developer

2017 - PRESENT
Freelance Work
  • Developed secure Solidity smart contracts for the Ethereum blockchain.
  • Conducted security audits of Solidity smart contracts.
  • Implemented interaction with Ethereum smart contracts using JavaScript and web3.
  • Created ICO smart contracts.
  • Acted as token economics consultant.
Technologies: Node.js, Truffle, Web 3.0, JavaScript, Solidity, Blockchain

Blockchain Architect | VP Engineering

2018 - 2019
Under NDA
  • Researched and implemented bleeding-edge blockchain technology including core blockchain development, network component development and development of revolving blockchain integrations.
  • Architected and led development of a blockchain platform based on Tendermint and Cosmos SDK with native KYC/AML support to be used in government applications.
  • Participated in the process of drafting a standard for an Inter Blockchain Communication protocol.
  • Conducted technical interviews and managed a remote team of 5-10 people and coordinated communication with other teams.
  • Interacted with multiple stakeholders in the process of analysing and defining business use cases.
Technologies: Amazon Web Services (AWS), JavaScript, Go,, BigchainDB, Cosmos SDK, Tendermint, Solution Architecture

CTO | Blockchain Engineer

2018 - 2019
  • Analyzed the user requirements and researched the electric power generation industry.
  • Consulted regarding blockchain choice and business tokenization.
  • Created a proof of concept in record breaking time.
  • Created a detailed estimate of blockchain transaction costs.
  • Researched, proposed and integrated several Ethereum Improvement Proposals (EIPs).
  • Developed backend services that mimic real world infrastructure.
  • Developed an fully functional decentralized application (DApp) with React.js frontend communicating with the Ethereum blockchain.
  • Implemented various transaction cost optimizations utilizing game theory principles.
  • Deployed a private PoA blockchain for closed beta testing.
Technologies: Docker Compose, Docker, Express.js, ERC-721, ERC-20, Node.js, React, Truffle, Web 3.0, JavaScript, Ethereum, Smart Contracts, Solidity, Blockchain

CTO | Blockchain Engineer

2017 - 2019
Best Millions
  • Coordinated development and developed a blockchain-backed international lottery platform infrastructure.
  • Conducted technical interviews and formed the technical development team.
  • Transformed user requirements into technical specifications and delegated development tasks.
  • Researched and developed efficient off-chain data storage and querying infrastructure with on-chain proofs.
  • Developed secure Ethereum smart contracts in Solidity with accompanying tests.
Technologies: MySQL, Solidity, Blockchain, Redis, Node.js

Blockchain Engineer

2018 - 2018
Under NDA
  • Researched Ethereum scaling solutions including payment channels and state channels with underlying theory of Conflict-free replicated data types (CRDTs).
  • Analyzed whitepapers describing different payment and state channel proposals.
  • Gathered requirements and analyzed trade-offs for different scaling solution proposals.
  • Improved an existing Layer 2 blockchain scaling protocol.
  • Worked on implementing a solution that optimizes existing payment channel implementations for low availability clients.
Technologies: MQTT, WebSockets, Node.js, TypeScript, JavaScript, Ethereum, Smart Contracts, Solidity, Blockchain

Blockchain Developer

2018 - 2018
  • Provided a comparative analysis of different blockchain technologies to be used on the project.
  • Consulted regarding the choice of blockchain and technology stack and presenting trade-offs.
  • Analyzed and implemented user requirements for medical business processes.
  • Deployed a Hyperledger Indy blockchain and implemented business logic for self-sovereign identity.
  • Reverse engineered Hyperledger Indy protocols and developed a proof of concept on top of Hyperledger Fabric and Hyperledger Composer.
  • Developed and deployed business networks with multiple participants built on top of Hyperledger Fabric with Hyperledger Composer.
  • Created maintenance scripts for analyzing and upgrading business networks.
  • Developed Docker deployment scripts for blockchain business networks.
  • Built and deployed a "blockchain bridge" that connects different blockchains and enables cross-chain integrations.
  • Developed and deployed Ethereum smart contracts including customized ERC-20 tokens.
Technologies: Docker, Node.js, Solidity, Ethereum, Hyperledger Composer, Hyperledger Fabric, Hyperledger Indy

Software Engineer

2016 - 2018
  • Designed architecture and developed a fast, reliable and scalable REST API for a cloud based recruitment and workforce management platform.
  • Introduced advanced resource planning features that take into consideration employee availability and a flexible platform for generating and maintaining user shifts.
  • Implemented tests, deployment scripts and maintained development, staging and production environments.
  • Developed scripts for live monitoring and reporting of different environments.
  • Performance enhancement with query optimization and caching.
  • Coordinated task development for backend features with other developers.
  • Conducted technical interviews with internship candidates.
  • Implemented web application features in React.js.
Technologies: React, JavaScript, Laravel, MySQL, PHP

Student Assistant

2014 - 2017
School of Electrical Engineering
  • Wrote semester development project proposals.
  • Mentored and consulted students regarding game development projects.
  • Assisted students during lab exercises in computer laboratories.
  • Tested students knowledge and graded their work.
  • Participated as a student assistant within several programming related and operating system related subjects.
Technologies: C++, C

Software Engineering Intern

2014 - 2014
  • Implemented declarative workflow automation features for core banking software platform.
  • Researched the Windows Server Service Bus and Workflow Manager platform and the way it has been embedded in the Microsoft Sharepoint Portal.
  • Sett up Proof of Concept VM environments for Workflow Manager, Service Bus and SharePoint.
  • Developed PoC proxy event analyzer of arbitrary Service Bus messages relayed to Workflow Manager.
  • Built metadata export/publishing command line tools used to move workflow definitions between different environments.
  • Created custom declarative activities that wrap calls to REST APIs.
  • Developed PoC sample workflow that uses mix of built-in and custom developed activities to orchestrate a sample scenario.
Technologies: Windows Workflow Foundation, Workflow, Oracle Service Bus (OSB), C#


2010 - 2013
Mikro Hosting
  • Piloted a one-man web hosting and domain registration service business.
  • Developed a web hosting account management and domain registration automatization software in PHP and MySQL. The system included a ticketing support center for customers.
  • Set up and maintained a Linux server including WHM, cPanel, PHP, Apache, backups, and more.
  • Provided customer support.
  • Contributed to financial planning.
Technologies: MySQL, PHP

Custom Proof of Work Blockchain

As a part of my master's thesis, I implemented a distributed proof of work blockchain in Node.js. I did a comparative analysis of the Bitcoin and the Ethereum blockchain, concluded main differences in their core blockchain way of operation, set requirements for a custom platform and developed it. I have analyzed in detail the difference of PoW algorithms and implemented my own including the miner process. While building the blockchain security considerations were made to stop malicious actors, censoring, reply attacks, etc.

Chatbot Hackathon 1st Place

Telenor organized the first Telenor Hackathon, within which 15 teams of programmers had the opportunity to develop a functional prototype of Facebook Messenger Chatbot application.

My team built an advanced chat bot which was announced as the best technical solution as well as best presented bot. The bot was build using various NLP techniques using Java and Node.js, to understand the question asked, and external APIs to provide a competent answer.

Reminder Chatbot

As a part of my bachelor's thesis, I implemented a software agent for social networks using natural language processing and machine learning techniques. The main functionality of the bot was parsing and analyzing user messages, executing reminders and providing a friendly user interface to end-users.

The bot was developed in Java using the Stanford NLP library. The database used was MongoDB.

The paper describing the process was published on the Telecommunications Forum (TELFOR) with the title "A software agent for social networks using natural language processing techniques"

IOPlac - Money Handling Kiosk

As a part of this project, I developed a functional payment kiosk for parking services. Apart from software development, I established the connections between the components. The kiosk has the ability to scan barcodes and RFID cards, receive cash and return change (both paper and coin), print different kinds of receipts with a thermal printer. The kiosks are connected to the main server through modern IoT protocols. The project was developed in Java and related technologies.

TrippyTap - Mobile Game

TrippyTap is a very fun and addicting puzzle and reflex game that was developed for the Firefox OS and Android platform. The Firefox OS version won the second place in an app competition, and the android version has experienced huge popularity in Bangladesh by being included in local provider application with over 5 million installs.


XBoost is a software agent that acts like a game server providing fake data to its clients and redirecting every connection to a real game server, thus increasing game server popularity. PHP was used both for the UDP server and the web control panel that had advanced management and billing functionality.
2018 - 2021

Progress towards a Ph.D. in Software Engineering

School of Electrical Engineering, University of Belgrade - Belgrade, Serbia

2016 - 2018

Master's Degree in Software Engineering

School of Electrical Engineering, University of Belgrade - Belgrade, Serbia

2012 - 2016

Bachelor's Degree in Software Engineering

School of Electrical Engineering, University of Belgrade - Belgrade, Serbia


Web3.js, Node.js, REST APIs, jQuery, Socket.IO, React


Git, Hyperledger Indy, BTC Wallet, Docker Compose, Slack, MQTT, WebStorm, PhpStorm


Truffle, Laravel, Express.js, Tendermint, Cosmos SDK, Windows Workflow Foundation, Redux


SQL, PHP, HTML, JavaScript, Solidity, Go, Java, C, C++, C#, TypeScript, Bash, CSS


Blockchain, Ethereum, Blockchain Platforms, Hyperledger Composer, Linux, Docker, Hyperledger Fabric, MacOS, Hyperledger, Amazon Web Services (AWS), Visual Studio Code (VS Code)


MySQL, BigchainDB, Redis, Memcached, MongoDB


Concurrent Programming, Parallel Programming, REST, Microservices


Elliptic Curve Cryptography, Public-key Cryptography, DApps, Smart Contracts, Cryptocurrency, Distributed Ledgers, Cryptocurrency APIs, Ethereum Smart Contracts, Customized Blockchains, Blockchain Architecture, Solution Architecture, HD Wallets, Quorum, Scaling, Cryptographic Protocols, Applied Cryptography, Cryptography, Bitcoin, IPFS, ERC-827, ICO, Distributed Systems, Chatbots, Cryptocurrency Wallets, Cryptocurrency Development, Data Structures, Algorithms, Mobile Wallet, IEO, Web 3.0, Oracle Service Bus (OSB), Workflow, ERC-20, ERC-721, WebSockets,

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