Definition
AES (Advanced Encryption Standard) is a symmetric block cipher standardised by NIST in 2001 that has since become the de facto global encryption standard. Symmetric means the same key encrypts and decrypts - unlike the asymmetric algorithms used in certificates and TLSCryptographic protocol that secures data in transit between two systems - the successor to SSL, and the reason data cannot be intercepted or altered along the way. handshakes. AES operates on 128-bit blocks with key lengths of 128, 192 or 256 bits; the number in "AES-256" is the key length, not the block size. Longer keys give greater resistance to exhaustive search, and AES-256 is what public procurement and security standards typically require. AES and TLS are not competitors but complementary layers: a TLS handshake uses asymmetric cryptography to agree a session key, then encrypts the traffic itself symmetrically - usually with AES.