Jakub Kubík
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Portfolio

Projects

Websites, research, university projects and a hobby project. Links go to the live site, source code or the publication.

Websites

ozjuliana.sk home page on desktop

P-01 · website2026

ozjuliana.sk

New website · design, development, operations

A website for a small non-profit that collects goods for people in need all year round – fast on mobile, with a simple news admin and no WordPress.

People from the non-profit post collection updates themselves, mostly from their phones.

47.4 kB

Home page HTML and CSS. Half of all mobile sites ship more than that in CSS alone (77 kB, HTTP Archive 9/2026).

Home page size after each change, April–October 2026 (38 versions).

  • Framework-free PHP, articles as JSON files, no database
  • Admin login with a password and Google Authenticator (TOTP in plain PHP)
  • Accessibility: 0 axe findings (WCAG 2 A/AA) in 30 runs over 10 pages
  • PHP
  • HTML
  • CSS
  • JavaScript
  • Apache

Live site : ozjuliana.skCase study : ozjuliana.sk

Redesign proposal in progress for the DentSpark.com home page (mockup, not published)
proposal

in progressP-02 · website2026

DentSpark.com

Existing shop · fixes and redesign proposal

A redesign and fixes for a Wix shop selling paintless dent repair tools. The product and search fixes are done; the FAQ draft and the new design are in progress.

The new design goes live in one go once the owner approves it; the shop keeps selling in the meantime.

151 messages

from the contact form, distilled into a 15-question FAQ draft

  • Done4 of 4 product pages fixed through the Wix API, a new main-product URL with a 301 redirect
  • In progressAn FAQ draft with 15 questions from 151 contact-form messages
  • In progressA redesign plan and A/B mockups, to go live in one go only once the owner approves
  • Wix
  • Wix API
  • SEO
  • HTML

Case study : DentSpark.comShop (original design)

Research

P-03 · research2023–2026

Selfish mining in blockchains

The simulation framework from my master’s thesis compares how the Nakamoto, Subchain and Strongchain protocols resist selfish miners. The paper in Springer LNCS 16231 (CBT workshop at ESORICS 2025) builds on it and evaluates Nakamoto, Fruitchain and Strongchain with multiple attackers.

  • Single- and multi-attacker scenarios
  • Open source in Python on GitHub (smasf)
  • Python
  • simulations

Paper (Springer LNCS) Full text on arXiv smasf on GitHub

Diagram: an attacker’s private branch grows next to the public chain of blocks.public chainattacker’s private branch

University

P-04 · university2022–2023

University projects (Brno University of Technology)

Projects from my cybersecurity master’s: simulating attacks on blockchains, machine-learning anomaly detection in industrial network traffic and a Dockerised monitor for peer-to-peer network nodes.

  • Python
  • scikit-learn
  • pandas
  • Docker

Applications

P-05 · application2020

Sequence Prediction Tool

A Chrome extension that predicted English text with a recurrent neural network running directly in the browser. Published on the Chrome Web Store in 2020; it is not available there today, but its listing is archived.

  • Model trained in TensorFlow, inference in tensorflow.js with no server
  • Built for my bachelor’s thesis at Brno University of Technology
  • TensorFlow
  • tensorflow.js
  • JavaScript

Bachelor’s thesis Archived Chrome Web Store listing (2025)

Infrastructure (hobby)

P-06 · hobby project2025 – present

Homelab

My own server where I practise running services the way it’s done at work: isolated services, monitoring, tested backups and documentation.