https://lesitedefrancois.be/en/tags/symmetric/Recent content in Symmetric on Le Site de FrançoisHugo -- gohugo.ioen© 2026 Françoishttps://lesitedefrancois.be/en/security/aes/Mon, 01 Jan 0001 00:00:00 +0000https://lesitedefrancois.be/en/security/aes/<p><strong>AES (Advanced Encryption Standard)</strong>, standardised as NIST FIPS 197 in 2001, is the symmetric block cipher that underlies virtually all data encryption in modern infrastructure. It was selected through a five-year open competition that evaluated 15 candidate algorithms; the winner, <strong>Rijndael</strong> (designed by Joan Daemen and Vincent Rijmen), became AES. A block cipher takes a fixed-size block of plaintext and a key and produces a fixed-size block of ciphertext — AES always operates on <strong>128-bit (16-byte) blocks</strong>, regardless of key size. Three key lengths are standardised: <strong>AES-128</strong> (128-bit key, 10 rounds), <strong>AES-192</strong> (192-bit key, 12 rounds), and <strong>AES-256</strong> (256-bit key, 14 rounds), providing 128, 192, and 256 bits of security respectively against classical attacks. AES-256 is the conservative choice for data with long confidentiality requirements and is mandated by CNSA 2.0 for national security systems; AES-128 is widely deployed in TLS and provides adequate security for most workloads. The internal structure — SubBytes, ShiftRows, MixColumns, AddRoundKey — is fully public and has withstood over two decades of cryptanalysis; the best known attacks against full-round AES are theoretical and computationally infeasible, requiring work far beyond brute force but not threatening practical security.</p>