AES

AES (Advanced Encryption Standard) is the symmetric-key block cipher used worldwide to encrypt stored data and internet traffic.

AES (Advanced Encryption Standard) is a symmetric-key block cipher: the same secret key both encrypts and decrypts the data, unlike RSA or elliptic curve cryptography, where a public key and a private key do different jobs. It processes data in fixed 128-bit blocks and supports three key lengths - 128, 192 and 256 bits - with 256-bit keys giving the largest security margin.

The algorithm was originally designed under the name Rijndael and became a US federal standard, published by NIST as FIPS 197, after an open, multi-year public competition among cryptographers. It replaced the older DES and 3DES ciphers and is now the default choice almost everywhere symmetric encryption is needed: disk and database encryption, VPNs, the bulk-data phase of TLS connections, and the protection of key material inside a hardware security module.

Because it is symmetric, AES needs the encrypting and decrypting parties to share the same key in advance, which is itself a distribution problem. In practice it is combined with asymmetric cryptography (PKI, TLS key exchange) that securely establishes a fresh AES key for each session, after which the bulk of the traffic is encrypted with AES because it is far faster than public-key algorithms.

Note: AES is a confidentiality tool, not a signing tool - it hides content but says nothing about who created it or that it has not been altered. Integrity and authenticity of a document are the job of hashing and an electronic signature, not of AES.