AES256 (Asymmetric Key Algorithm)

AES-256 is the 256-bit key variant of the Advanced Encryption Standard, a symmetric block cipher that the U.S. National Institute of Standards and Technology standardized in 2001 (FIPS 197) to replace the aging DES. Unlike an asymmetric key algorithm, which uses a mathematically linked public and private key pair, AES-256 encrypts and decrypts with one shared secret key, making it far faster and cheaper to run on ordinary hardware.

The algorithm processes data in fixed 128-bit blocks through 14 rounds of substitution, row-shifting, column-mixing and key-mixing operations, expanding the original 256-bit key into a series of round keys via the Rijndael key schedule. With 2^256 possible keys, brute-forcing AES-256 is considered computationally infeasible even for large-scale attackers, which is why it remains the baseline symmetric cipher in the NSA's Commercial National Security Algorithm Suite and in most government and banking systems.

In crypto specifically, AES-256 rarely stands alone. Wallet software commonly uses it to encrypt a private key or seed phrase at rest on a device, while protocols such as TLS pair it with an asymmetric handshake: RSA or elliptic-curve key pairs negotiate a temporary shared secret, and AES-256 then does the heavy lifting of encrypting the actual session traffic. This combination balances the strong key distribution of asymmetric cryptography with the raw speed of symmetric encryption.

AES-256 should not be confused with hashing algorithms like SHA-256, which produce a fixed-size fingerprint of data and cannot be reversed to recover the original input; AES is reversible by design, given the correct key.