AES stands for Advanced Encryption Standard, and 256 refers to the key length in bits. It is a symmetric encryption algorithm adopted by NIST in 2001 after a rigorous five-year public competition. The open selection process and decades of cryptographic scrutiny are a large part of why AES is so widely trusted today.

How AES Works

AES operates on fixed-size blocks of 128 bits. For AES-256, the algorithm applies 14 rounds of mathematical transformations: SubBytes (nonlinear substitution), ShiftRows (row shifting), MixColumns (column mixing), and AddRoundKey (key mixing). These operations work together to thoroughly scramble the data so that the output reveals nothing about the input.

The Key Space

A 256-bit key has 2^256 possible values — approximately 1.16 x 10^77. Even a hypothetical computer testing a billion billion keys per second would take longer than the age of the universe to try them all. This mathematical reality makes AES-256 practically unbreakable through brute force.

Modes of Operation

AES encrypts single blocks, but real data is larger than one block. Modes of operation like GCM (Galois/Counter Mode) define how to apply AES to arbitrary-length data. GCM provides both confidentiality and integrity — it encrypts data and detects any tampering. When evaluating encryption software, look for AES-256-GCM.

Key Derivation

In practice, you provide a password, and a key derivation function transforms it into a 256-bit key. Modern KDFs like Argon2 are deliberately slow, making brute-force password guessing impractical. The quality of key derivation is as important as the encryption algorithm itself.

The Quantum Question

Grover’s quantum algorithm could theoretically halve AES key lengths — AES-256 would offer 128-bit security against quantum computers, still far beyond practical attack capabilities. This quantum resistance is a key reason AES-256 is preferred for long-term data protection.

AES in Everyday Life

You interact with AES encryption constantly — HTTPS web traffic, phone storage encryption, VPN connections, and banking transactions all use AES. LockWhisper uses AES-256 to protect all data on your iOS device, providing the same encryption standard trusted worldwide.