I. Who am I?

Hello everyone. My name is Gurur Yetişkin and I'd like to start by briefly introducing myself. I've been involved in the cybersecurity field since 2017. My journey began when I received a prestigious merit-based scholarship that gave me the opportunity to study in Belgium and France. During my time there, I gained both academic knowledge and my first hands-on experience in the industry.

After returning to Turkey, I worked at Big Four firms and in the banking sector. For the past five years, I've been working in cybersecurity within the cryptocurrency industry, where I continue to build my career today. Throughout my professional journey, I've earned several certifications including CISM, OSWE, OSWP, CEH, BHWH, SAST, MCP, and various ISO certifications.

In this video series, we'll dive deeper into the technical side of cybersecurity. Rather than focusing solely on theoretical concepts, I'll also share real-world scenarios, challenges I've encountered, and the technical approaches used to address them.

At a time when artificial intelligence is becoming increasingly central to content creation, I want to focus on producing content that is as independent of AI as possible, grounded in my own research, hands-on experience, and technical analysis. My goal is to go beyond memorized concepts, explore the reasoning behind how things work, and approach cybersecurity from a more technical, analytical, and critical perspective. I hope this series will be both valuable and educational for all of us. Now, let's get started.

II. What are we going to cover?

Before we dive into real-world cryptocurrency hacks, security vulnerabilities and technical incidents, I believe we need to understand something fundamental: how does the financial system actually work? And why was blockchain technology introduced in the first place? Without understanding the underlying technology, it's difficult to fully understand the security problems surrounding it.

In this first episode, we'll cover five main topics:

  • Traditional finance: also known as TradFi, and how banks and financial institutions process transactions.
  • The emergence of blockchain: the origins of Bitcoin and the concept of decentralization.
  • How blockchain actually works: transactions, digital signatures, nodes, blocks, and consensus mechanisms.
  • Beyond Bitcoin: Ethereum, smart contracts, and decentralized finance.
  • Cybersecurity: why blockchain-based systems can still be vulnerable to real-world attacks.

The goal of this episode isn't to turn everyone into a blockchain developer. Instead, I want to build a solid technical foundation that will help us understand the more advanced security topics we'll explore in future episodes. So, let's begin with something we're already familiar with: traditional finance.

III. Traditional finance (TradFi)

Imagine you want to send money to someone living in another country. You open your banking application, enter the recipient's information, specify the amount, and confirm the transaction.

From your perspective, the process seems pretty simple. You press a button, and the money is sent. But have you ever wondered what actually happens behind the scenes? How does the bank know that you have enough money? Who verifies the transaction? And how does the money reach another bank, especially when that bank is located in a different country?

To answer these questions, we need to understand how traditional financial systems operate. Traditional finance, commonly referred to as TradFi, describes the financial ecosystem built around established institutions such as banks, payment providers, clearing systems, and other financial intermediaries. These institutions play an essential role in processing payments, maintaining financial records, and providing access to financial services.

IV. Following a transfer

Let's go back to our example. You want to send money from your bank account in Turkey to someone in another country. Depending on the banking infrastructure and the payment method, your transaction may involve several different institutions:

Your bank initiates the payment.
An intermediary bank may participate in routing or settling the transfer.
A payment messaging network may carry the instructions between institutions.
Eventually, the receiving bank credits the beneficiary's account.

Of course, not every transfer follows exactly the same process. Some payment systems are much faster and more direct than others. But the important point is that the process depends on a network of financial institutions and their records.

V. What your balance really is

Now, let's look at another example. When you open your banking application and see a balance of $1,000, what exactly are you looking at? You're not looking at a physical stack of money sitting inside your phone. You're looking at a financial record maintained by your bank. That record represents the amount available in your account according to the bank's systems.

When you send money to someone else, the relevant financial institutions update their records according to the transaction. In other words, traditional finance relies heavily on trusted institutions maintaining accurate financial ledgers.

VI. Trust, and its limits

This introduces an important concept: trust. You trust your bank to maintain accurate records. You trust payment systems to process transactions correctly. And you trust the institutions involved to follow applicable rules and security requirements.

Centralization isn't necessarily a bad thing. Traditional finance provides important advantages, including regulatory oversight, consumer protections, fraud monitoring, and established financial infrastructure.

However, centralized systems also have certain limitations:

  • International payments can sometimes take days to complete.
  • Transactions may involve fees from multiple institutions.
  • Access to financial services may be restricted by geography, regulations, or institutional requirements.
  • Users generally depend on financial institutions to maintain and update their account records.

This leads us to a very interesting question. What if we could transfer digital value directly between participants without relying on a single central institution to maintain the transaction history? And more importantly, what if a network of independent computers could collectively verify and maintain those records?

This question brings us to the next part of our discussion.