What Is AES-256 Encryption? How Does It Work?

Encryption is critical for overall internet security. There are different encryption systems in use today, but they all generally work by scrambling data with the help of a mathematical algorithm, encrypting information into code.

One of the most common encryption standards today is the Advanced Encryption Standard (AES). It’s a variant of the Rijndael block cipher and is available in three key sizes: 128, 192, and 256 bits.

So, what is AES-256 encryption, and how does it work?

What Is AES?

AES is a widely adopted data encryption standard that’s in use worldwide. It’s the federal standard used by the United States government, and it offers significant security and protection.

AES is a type of symmetric encryption, which uses the same key to encrypt and decrypt your data. Essentially, both the sender and the receiver require the same key to decrypt the data. Symmetric encryption is faster, though it’s a bit less secure than asymmetric encryption.

What Is a Block Cipher?

To understand how AES-256 works, it’s important to understand block ciphers. A block simply means a unit of information divided before it’s encrypted. Standard AES uses a 128-bit block size.

To visualize, 16 bytes multiplied by 8 bits gives you 128 bits in every block. So no matter the key size, the size of the block remains the same. AES has suffered quite a few attacks but hasn’t been cracked yet.

AES-256 is the most secure version, although it requires greater computing power. Given the looming threat of post-quantum cryptography, many consider AES-256 quantum-resistant, which means that quantum computers aren’t expected to crack the cipher.

How Does Block Size Affect Security?

The size of the block also has an indirect effect on the security of the cipher. Essentially, the larger the block, the more data can be encrypted without it being duplicated. But, if the block size is too small, it can impact the cipher’s secure usage.

A block cipher is meant to be a pseudorandom permutation, which simply means that if inputs are different, the outputs should automatically differ too. AES primarily uses a 128-bit block size, where data is divided into a 4×4 array containing 16 bytes.


However, while block size doesn’t directly impact cipher security, it does impact mode security. All block ciphers are generally deployed in different modes of operation, so the security of each mode depends on two elements: the security of the block cipher itself and the security of the mode when the block cipher’s replaced with a pseudorandom permutation.

Essentially, the more data you process within a mode of operation, the more it exposes the mode as the shorter block size results in an increase in opposing success probability. Over time, parts of the permutation, which are hidden, continue to get exposed, eventually revealing the full permutation.

So, if you have a block cipher of N bits, and you know that it’s no different from a pseudorandom permutation of N bits, the security of your cipher will suffer if you use it in a mode of operation. To ensure that mode security isn’t affected, it’s best to use a larger block size.

How Does AES-256 Encrypt Your Data?

The basic concept of encryption is that the cipher replaces each unit of information with another one, depending upon the security key. For example, AES-256 completes 14 rounds of encryption, making it incredibly secure.

The steps involve dividing the data into blocks, replacing different bytes, shifting rows and mixing columns, to scramble the information completely. By the end of the process, the result is a completely random set of characters that won’t make sense to anyone if they don’t have the decryption key.

AES-256 is the longest and is also the strongest level of encryption that it offers. To put things in perspective, a hacker would need to try out 2256 discrete combinations, each with a total of 78 digits, to break through the encryption.


In essence, the number is bigger than the number of stars in the universe! This makes it impervious to brute force attacks and is the most powerful encryption standard in the world.

Applications of AES-256

AES-256 is the most robust variant, so it’s not always ideal for simple application use. However, AES-256 is used by VPN providers and for securing databases.

AES libraries are available for popular programming languages ​​like C, C++, Java, and even Python. If you use a password manager like 1Pass or LastPass, you’re probably already using AES-256 to encrypt sensitive information.

Even messaging apps like WhatsApp use AES-256 encryption to scramble messages. Modern computers that use Intel or AMD processors already have AES instructions built-in, and almost all financial institutions rely on AES encryption to scramble sensitive information.

In short, AES is everywhere.

Encryption Is Only Going To Get Stronger

As the world moves towards decentralization and hackers get more creative, encryption standards will only get stronger. Already, cryptographic standards require public and private keys to verify transactions, so you can only expect security standards to get even better.

New Technology Era

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