AES
acronymcryptography
Stands for: Advanced Encryption Standard
The standard symmetric block cipher used almost everywhere for bulk encryption.
Advanced Encryption Standard (NIST FIPS 197), originally the Rijndael cipher, encrypts data in 128-bit blocks with 128-, 192-, or 256-bit keys. It is the workhorse behind TLS record protection, disk encryption, and VPNs.
AES is the block cipher almost everything uses, standardized by NIST in 2001 after an open international competition, and it has resisted practical cryptanalysis ever since. Modern processors implement it in hardware, so it is typically faster than the software alternatives people reach for when they think they are optimizing.
The number in AES-128 or AES-256 is the key length, not a quality rating, and 128 remains entirely adequate against classical attack. The usual reason to choose 256 is a policy requirement or a post-quantum argument, since Grover's algorithm would halve effective symmetric security, making 256 behave like 128 against a quantum adversary. That is a far gentler degradation than public key cryptography faces.
The mistake that actually causes breaches is the mode, not the cipher. AES alone encrypts a block; how blocks are chained determines whether the result is secure. ECB mode leaks structure so visibly that the same image encrypted with it remains recognizable, and CBC without authentication invites padding oracle attacks. Modern practice is an AEAD mode such as GCM, where encryption and authentication happen together and the remaining discipline is never repeating a nonce.
Also known as: aes, Rijndael