DeFi + TradFi = ♡

Comprehensive Smart Contract Audit with Certora Formal Verification

Wed, 17 Dec 2025 08:36:59 +0000

Hey guys, in this blog post, we’re going to perform a security assessment of a smart contract and, with the help of Certora’s formal verification tool, try to prove there are no “High” severity issues residing in the source code.

Replaying Bugs With Certora: Sorra Finance

Fri, 23 May 2025 09:38:30 +0000

In this blog post we’re going to deep dive into the Sorra Finance hack, find the root cause of the bug and create a certora rule which could’ve prevented the exploit.

Research: ERC20 Self Transfer

Tue, 13 May 2025 08:57:43 +0000

Overview

In this blog post we’re going to:{{ double-space-with-newline }}1. Understand how ERC20 self transfer vulnerability works in smart contracts{{ double-space-with-newline }}2. Create a semgrep rule for finding such contracts{{ double-space-with-newline }}3. Scan https://github.com/tintinweb/smart-contract-sanctuary to better understand how many contracts exist with such bug

How to create your own Uniswap

Fri, 20 May 2022 16:10:00 +0000

In this tutorial we’re going to build a very basic decentralized exchange (DEX) like Uniswap or PancakeSwap.

How to create your own ERC721 NFT collection and publish it on Opensea

Sat, 09 Apr 2022 15:58:00 +0000

In this tutorial we’re going to create our own ERC721 NFT collection and publish it on the Opensea marketplace.

HTB Validation writeup

Thu, 23 Sep 2021 22:02:33 +0000

In this tutorial we will get root access for the Validation machine from Hack The Box.

Web penetration testing

Tue, 21 Sep 2021 15:00:05 +0000

In this tutorial we’re going to define base steps for web penetration testing and find vulnerabilities in DVWA.

Network penetration testing

Sat, 11 Sep 2021 10:04:28 +0000

In this tutorial we’re going to identify running services on the target server and try to exploit them.

Passive information gathering

Tue, 07 Sep 2021 22:55:09 +0000

The 1st step of any penetration test is gathering information about the target company. In this tutorial we will go through all the steps required for passive information gathering.

Android reverse engineering

Wed, 01 Sep 2021 00:12:22 +0000

Hello everybody. In this tutorial we’re going to reverse engineer a vulnerable android app, find all vulnerabilities and create a report.

Your first Ethereum smart contract

Sat, 06 Jan 2018 23:01:48 +0000

In this tutorial we are going to write a smart contact in Solidity language that can prove file ownership.

Comprehensive guide to Redis. Part 6.

Tue, 15 Dec 2015 21:48:55 +0000

In this tutorial, we are going to vet some common pitfalls when using Redis.

Converting pdf file to html canvas with text selection using PDF.js

Mon, 07 Dec 2015 18:10:21 +0000

In this tutorial, we are going to display a pdf file inside an html canvas object with the ability to select the text in the page.

Comprehensive guide to Redis. Part 5.

Sun, 29 Nov 2015 19:31:21 +0000

In this tutorial, we are going to try out a Redis client library for PHP. Unlike the Node.js client we used in the previous tutorials, the chosen PHP client library is synchronous and do not require a callback function.

Comprehensive guide to Redis. Part 4.

Thu, 19 Nov 2015 13:32:51 +0000

In this tutorial, we are going to overview other Redis commands and features.

Comprehensive guide to Redis. Part 3.

Sun, 08 Nov 2015 21:42:09 +0000

A time series is an ordered sequence of values that are made over a time interval. You can use time series in statistics, communications, and social networks. I this tutorial we are going to create a simple stock time series Node.js library using Redis Strings. This library records events per second, minute, hour, and day.

Comprehensive guide to Redis. Part 2.

Mon, 02 Nov 2015 12:07:48 +0000

In this tutorial, we are going to discover a few more data types like Set, Sorted Set, Bitmap, and HyperLogLog.

Comprehensive guide to Redis. Part 1.

Sat, 24 Oct 2015 09:48:40 +0000

Redis (REmote DIctionary Server) is an advanced key-value data store. Read and write operations in Redis are very fast because it saves all data in the memory. Redis can also save data on the hard drive. The official Redis documentation can be found at http://redis.io. Redis is an open sources project used by many companies including Instagram and Twitter. In this tutorial, we will install Redis, install Node.js, and try out several data types.

Comprehensive guide to WebRTC. Part 5/5.

Fri, 09 Oct 2015 14:09:53 +0000

In this tutorial, we are going to focus on the transferring arbitrary data using WebRTC Data Channel Protocol.

Comprehensive guide to WebRTC. Part 4/5.

Thu, 01 Oct 2015 09:11:56 +0000

In this part we are going to create a client application which connects two users using signalling server we created in the previous part.

Comprehensive guide to WebRTC. Part 3/5.

Fri, 25 Sep 2015 12:06:47 +0000

In this tutorial we are going to create a basic signalling server using javascript and nodejs. It will be able to connect two users together.

Comprehensive guide to WebRTC. Part 2/5.

Fri, 18 Sep 2015 10:46:15 +0000

The first thing of any WebRTC app is creating an RTCPeerConnection. Creating an RTCPeerConnection will help us to understand the inner workings of peer connections inside the browser.

Comprehensive guide to WebRTC. Part 1/5.

Fri, 11 Sep 2015 10:41:45 +0000

WebRTC (Web Real-Time Communication) is your browser built-in technology with the aim to simplify developing applications using audio and video streams. You can easily build your own Skype in the browser using WebRTC. So the simple idea is that you open up a website and connect with another user immediately. WebRTC API includes camera and microphone capture, video and audio encoding and decoding, transportation layers, and session management.

Getting started with Kurento WebRTC

Tue, 01 Sep 2015 15:20:43 +0000

Today we are going to try kurento media server and create a simple webrtc application.

Kurento is an open-source media server with WebRTC support. So if your customer wants to integrate video/audio chat on his website Kurento may solve this problem.

Creating HTML parser using golang

Wed, 05 Aug 2015 19:35:06 +0000

This time we are going to create a HTML parser for http://www.flashscore.com/ .

Getting started with Arduino

Sat, 13 Jun 2015 11:56:18 +0000

In this tutorial we are going to create our first arduino project. It will be a simple blinking light-emitting diode.

Changing the expiration date of the 1C Bitrix CMS

Thu, 04 Jun 2015 12:16:37 +0000

Sometimes it is necessary to prolongate standard Bitrix test period because when developing a large project 30 days are not enough.

Contact

Sat, 16 May 2015 19:59:39 +0000

email: ryzhak.vladimir@gmail.com
telegram: @vryzhak

Blog

Sat, 16 May 2015 19:59:17 +0000

About

Sat, 16 May 2015 19:59:07 +0000

Hi guys! I am Vladimir, full stack developer from Krasnodar, Russia. At the moment I’m working at Ticketscloud. Feel free to contact me.

Vladimir Ryzhak - Blockchain Engineer

Sat, 16 May 2015 19:58:30 +0000

Tech Blog

AZI

Mon, 01 Jan 0001 00:00:00 +0000

AZI is an online card game. Rules are similar with Texas Holdem Poker, but with a few changes. My task was to develop backend for the game, API to communicate with desktop, android and ios apps, website and admin part of the website to make and monitor transactions, payments, users and other stuff.

BetOnRefs

Mon, 01 Jan 0001 00:00:00 +0000

BetOnRefs is a web and iOS app for predicting number of bookings and red cards in football matches.

BookieBeater

Mon, 01 Jan 0001 00:00:00 +0000

BookieBeater is a service for predicting football results. You can also watch football video streams using this service. All predictions are made with the help of neural networks and teams’ statistics. There are 13 football leagues available for prediction at the moment.

CV

Mon, 01 Jan 0001 00:00:00 +0000

Vladimir Ryzhak

DeFi Engineer

Contacts

Summary

Senior Blockchain and Full-Stack Engineer with 12+ years of experience architecting decentralized applications, smart contracts, and scalable microservices. Proven track record of leading technical strategy—from launching a fully functional USD-pegged stablecoin to building custom DAO frameworks and enterprise-grade ticketing platforms. Passionate about bridging Web3 innovation with robust, production-grade engineering, with a strong emphasis on security auditing and team leadership.

Dobrokassa

Mon, 01 Jan 0001 00:00:00 +0000

My task was to create a CRM to help people cut their overdue loans. The following features were implemented: RBAC, user management, notifications, payments and integration with the national bureau of credit histories.

Dominator Slots

Mon, 01 Jan 0001 00:00:00 +0000

Dominator is a gambling game resembling classic slots. My task was to create a technical specification, API for mobile apps, CRM for managing users and finances.

Fans in Tears

Mon, 01 Jan 0001 00:00:00 +0000

Fans in Tears is a mobile app for football fans with memes, chats, social features and telegram bot.

FC Krasnodar Medicine Application

Mon, 01 Jan 0001 00:00:00 +0000

FC Krasnodar medicine application is a CRM developed to monitor the usage of medicines by football players. My task was to develop backend and frontend parts of the web-application and transfer a database from the old version of the program to the new one.

Lawyer CRM

Mon, 01 Jan 0001 00:00:00 +0000

My task was to develop a CRM for a law company. The following features were implemented: RBAC, i18n, client application management, notifications and event log.

Psyline

Mon, 01 Jan 0001 00:00:00 +0000

PSYLINE is an online service for psychological help. My task was to integrate WebRTC video and audio broadcasting, save video and audio streams on the server, setup video conferencing and webinar support in order to connect together psychologists and their clients.

Totallo

Mon, 01 Jan 0001 00:00:00 +0000

Totallo is a web service for creating accumulator bets with the highest probability. It parses statistics of nearly 500 teams, creates a neural network for each team and makes accumulator bets with the highest probability of goals count scored in a single game.