Hello everyone. It's been quite a while since I last wrote something here.
Today I want to talk about something really interesting in cryptography: why no cryptographic algorithm survives forever, and how cryptography keeps evolving with technology.

The Rise and Fall of Old Algorithms

DES (Data Encryption Standard)

Back in the late '70s, DES was the standard. Everyone used it. Governments approved it. It felt unbreakable.

Then in 1998, it was publicly broken. The key size (56-bit) had simply become too small for the computing power of the time. What once took years to brute-force could now be done in hours.

RC4

RC4 was fast and simple — perfect for streaming data. It was widely used in protocols like SSL/TLS and WEP (Wi-Fi).

By 2001, serious weaknesses started showing up. Over the years, the attacks only got better. Eventually, major browsers and standards bodies deprecated it completely. Another once-popular algorithm sent to the graveyard.

Triple DES (3DES)

After DES died, we didn't jump straight to AES. Instead, we tried extending DES's life by running it three times (hence the name). It worked as a temporary fix.

But by 2016, even Triple DES was considered too weak for most practical purposes. The security margin just wasn't enough anymore.

Where We Stand Today: AES

Right now, AES (Advanced Encryption Standard) is the most used one, and honestly, it's holding up very well. Most modern systems use AES-128 or AES-256.

But until now, we were only talking about symmetric encryption — where the same key is used for both encryption and decryption.

Things become much more interesting when we move into asymmetric cryptography.

One of the most famous asymmetric algorithms is RSA. The name actually comes from the first letters of its creators: Rivest, Shamir, and Adleman.

Unlike AES, RSA uses two different keys:

• one public key for encryption
• one private key for decryption

And you can't simply reverse their roles.

At first, RSA might sound strictly better than AES. After all, sharing a public key sounds much safer than sharing a secret key directly.

But there's a catch.

AES is extremely fast. RSA is comparatively slow.

That's why, in real-world systems, we usually combine them together:

• AES encrypts the actual data
• RSA securely exchanges the AES key

This hybrid approach is basically how much of modern secure communication works today.

Recently I've been learning more about cryptography and PQC (Post-Quantum Cryptography), and honestly, this part of cryptography became much more fascinating to me once I started understanding the history behind it.

Before this, I knew about RSA and AES individually, but I never really understood how cryptography constantly evolves.

The Real Lesson

The history of cryptography teaches us one important thing:

No algorithm lasts forever.

Every cryptographic standard is basically a temporary agreement between mathematics, hardware limitations, and the current state of computing power. Eventually, technology catches up.

I’ll probably make this a small series because the deeper I learn about cryptography and post-quantum systems, the more interesting the entire field becomes.

In the next post, I’ll talk about the Post-Quantum era and how researchers are trying to build cryptographic systems that can survive it.