What is AES-256 encryption? | Tom’s Guide
You may have seen some VPN providers boasting about using AES-256 encryption, but it’s not immediately apparent what this means or how it helps keep your data safe.
Essentially, VPNs use encryption to make sure that third parties can’t read your internet traffic while it’s travelling between your computer and whatever online service you’re accessing.
AES-256 is one of the most secure encryption standards available today, and is the industry standard when it comes to protecting data. You’ll often see it referred to as “military grade,” but it’s also used by banks, the government, and even common apps like WhatsApp and Signal.
That’s why the best VPNs use AES-256 to keep your data private when it’s being transferred. Here, we’ll be going over exactly why AES-256 is considered so secure, as well as how it works and why it’s a necessary part of your VPN connection.
What is AES-256 encryption?
AES-256 is a highly secure encryption protocol that is used to power private communication software across the globe, which of course includes VPN providers.
It was developed by the National Institute of Standards and Technology (NIST) in 1997 as part of an initiative to replace the US government standard at the time, DES, with a new, stronger encryption standard less vulnerable to brute force attacks.
AES stands for Advanced Encryption Standard, and the “256” in AES-256 refers to the length of the encryption key, which consists of 256 bits.
There’s so much confidence in the mathematics behind AES-256 that the NSA has approved it for encrypting top-secret classified documents.
The security of AES-256 stems from its large key size, making it virtually impossible to crack using brute-force attacks. While other encryption protocols like ChaCha20 prioritize speed and efficiency, AES-256 is specifically optimized for security.
The most private VPNs will only offer encryption protocols that are known to be bullet-proof against decryption attacks, which is why AES-256 is so popular as an encryption method.
There’s so much confidence in the mathematics behind AES-256 that the National Security Agency (NSA) has approved it for encrypting top-secret classified documents.
How does AES-256 encryption work?
AES-256 encryption takes a file or stream of data that you want to encrypt and transforms it using a “key,” so that the data you end up with is completely unreadable and totally different from what you started with.
The number at the end of AES refers to how large the key used to carry out this operation is in terms of bits. Larger keys are harder to break, so using 256-bit keys gives you the maximum amount of security against cryptographic attacks. Currently, even the most advanced supercomputers are unable to break AES through brute force.
AES-256 encryption operates using a symmetric key encryption system, which means that the same key is used to both encrypt and decrypt data. Essentially, decrypting a file with the same key just means applying all of the processes used to encrypt the key in reverse.
You might use a normal string password if you’re using AES-256 to encrypt or decrypt a file, but this password is transformed into a true 256-bit key before the algorithm actually begins.
The encryption process involves blocks of multiple steps, with each block being referred to as “rounds.” Each round involves a series of transformations which are repeated between rounds, with the difference being that every round uses a new 128-bit key derived from the overall master 256-bit key used to carry out the process.
The actual process is as follows:
- The target data is segmented into 128-bit blocks for processing.
- Each 128-bit block is transformed into a 4×4 byte array for which is used as input for each round. AES-256 uses 14 rounds of encryption.
- For every round, the scheduled round key is broken into a similar byte array and applied to the original block using an XOR operation.
- The bytes in the block then go through substitution, transposition, and mixing.
- Once the rounds have been completed on every block, the target data is considered encrypted.
This is still a slight simplification of how AES-256 actually works, but you can check out the original NIST publication if you need more detail.
Why is VPN encryption important?
Encryption is arguably the most important part of any VPN product. When you connect to a VPN, your data is encrypted before leaving your device. Without strong encryption, all of your data would be visible to prying eyes like your ISP, governments, and even potentially hackers.
Encryption algorithms like AES keep the secure tunnels you need to route your traffic through completely safe. AES-256 is virtually impenetrable by current standards, which is why the US government has trusted the algorithm for so long.
It’s not just the government, either: militaries, banks, and corporations across the world trust AES-256 to keep their data secure. Most secure VPNs will offer OpenVPN with some form of AES implemented, but for total confidence you should look for AES-256.
AES is only part of the puzzle though. It’s a symmetric key algorithm, so there’s one flaw with it.
It’s not just the government, either: militaries, banks, and corporations across the world trust AES-256 to keep their data secure
Anyone who has the password can encrypt and decrypt data at will. That means it’s unsuitable for starting up an encrypted connection, as you’d have to send the password over an unencrypted line to the other party you want to communicate with. This is where RSA, which is an asymmetric key algorithm, comes into play.
Because the encryption and decryption keys for RSA are different, you can send your AES keys encrypted using someone else’s encryption key knowing only they can decrypt it with their private decryption keys.
The reason we don’t use RSA for securing traffic tunnels is that it’s a relatively expensive, slow algorithm. AES, on the other hand, has been built from the ground up to be an extremely fast algorithm that can run even on relatively low-power systems without trouble.
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