AES-256 vs. ChaCha20

If you’re looking for a VPN and have been comparing providers, you’ve probably encountered the terms “AES-256” or “ChaCha20” encryption. These are called ciphers, and VPNs have used them to market that they have strong, industry-standard encryption.

But what do these terms actually mean? And more importantly, is one better than the other at encrypting and securing your connection? 

The truth is a little more nuanced than "pick the stronger one." 

Both ciphers have been studied and tested for decades, and they’re still used today to protect everything from banking apps to classified government data. As of writing, no one has found a way to break their protection. 

As someone shopping for a secure VPN, here’s what you should know about these two encryption technologies and how they protect your data.

What Is AES-256?

AES stands for Advanced Encryption Standard. AES is based on the Rijndael cipher, designed in the late 1990s by Belgian cryptographers Joan Daemen and Vincent Rijmen, and adopted as the US standard in 2001. This standard has been used by the US government to protect classified federal information since 2003. 

It’s also the same technology used by password managers like Dashlane and encrypted messaging apps like Signal. 

AES-256 works by breaking your data into small chunks and scrambling each one 14 times over using a 256-bit key—hence the 256 part in AES-256. This key is too long for any modern computer to crack. 

Because no cryptographer has found a weakness in it in its more than two decades of existence, it remains the go-to industry standard. 

Most modern communication devices come with built-in hardware that allows AES-256 to encrypt and decrypt your data almost instantly. This protects your device with practically no loss in speed and performance.

What Is ChaCha20?

On the other hand, ChaCha20 was created by cryptographer Daniel J. Bernstein in 2008 as a faster, simpler option than the ciphers that came before it.

While AES scrambles data into chunks, ChaCha20 instead creates long streams of randomized characters that get mixed with your data as it gets transmitted.

In VPNs and messaging apps, ChaCha20 is almost always paired with a second step called Poly1305, which checks that your data hasn't been altered during transit. Together, they’re usually called ChaCha20-Poly1305.

The main advantage of ChaCha20 is that, unlike AES, it doesn't need any special hardware to run quickly. It was specifically designed using simple math operations that regular processors already handle efficiently. ChaCha20 is the cipher of choice for most modern, lightweight VPN protocols.

Which One Is More Secure? 

There is no direct answer to this question because neither has been broken, and neither is expected to be anytime soon. Researchers have tested both for over a decade without a meaningful crack showing up.

The only theoretical way to crack either cipher is by trying every possible key, but that would take, quite literally, billions of years even for the most powerful computers, or even if every computer on Earth worked on it at once.

Even when looking ahead to the rise of quantum computers, the two are expected to remain safe for at least the foreseeable future. For example, when the National Institute of Standards and Technology rolled out its new post-quantum encryption standards in 2024, the focus was almost entirely on replacing other types of encryption, not ciphers like AES or ChaCha20. Simply using a long enough key, like 256 bits, is already enough to stay ahead of quantum computers.

For all intents and purposes, and based on every possible metric, both ciphers are equally secure. These two are the strongest encryption options a VPN can offer you. 

Where The Real Differences Show Up

That doesn’t mean there are no differences between the two, however. Despite being more or less equally secure, they differ in speed depending on the device you’re using. It’s why different VPN protocols make different choices.

As mentioned, AES-256 tends to run faster on devices built with dedicated encryption hardware, which most modern desktops and smartphones have. In one 2015 test, Cloudflare found that ChaCha20-Poly1305 ran roughly three times faster than AES on mobile devices, which typically lack the dedicated encryption hardware built into modern desktops and laptops.

Meanwhile, ChaCha20 will run faster on devices without that hardware. Examples include older phones, budget routers, and some smart home devices. The newer, fast, and lightweight VPN protocols typically use ChaCha20 exclusively. By contrast, older and more established VPN protocols like IKEv2/IPsec usually use AES-256 by default, but can be set up to use ChaCha20 instead on devices without dedicated AES hardware.

What This Means for Choosing a VPN

Practically speaking, a VPN’s cipher isn’t worth spending much time worrying about—or any time at all, really. AES-256 and ChaCha20 are the two strongest ciphers currently available for securing internet traffic, as neither has been cracked to this day. Either will protect you just as effectively as the other in any real-world scenario and will keep your data encrypted and unreadable as long as things are set up correctly. 

Still, there may be some slight speed differences in certain scenarios. As mentioned, ChaCha20 tends to run a bit faster on older devices without dedicated AES-256 encryption. On such devices, using a protocol that defaults to AES-256, like IKEv2, can lead to a bit of lag or extra battery drain. If your connection feels slower with the VPN on than off, it's worth switching to one of the newer lightweight protocols, which default to ChaCha20.

With that said, many VPN apps just default to "Automatic” and pick a protocol for you based on your network conditions. The option to manually select a protocol is often buried under "Advanced" settings since most users never touch it, which is a testament to the fact that the difference in security is nonexistent, and even the difference in speed is often barely noticeable.

Despite the technical nuances, the encryption algorithm is rarely the deciding factor in your overall digital security, and other features matter far more. Does it have a no-logs policy audited by independent, credible third parties? How open is the VPN company about how it operates? Is it owned by a parent company with other business interests in advertising or data collection? 

These questions are more impactful on your actual privacy than the encryption algorithm.