AES

AES is a symmetric-key block cipher that encrypts 128-bit data blocks with 128-, 192-, or 256-bit keys. It replaced DES as a widely used encryption standard.

Substitution–permutation network: A cipher structure that repeatedly combines substitutions and permutations to transform data. AES uses repeated substitution and permutation operations to transform each block.
DES: A 1970s block cipher with a 56-bit key, later vulnerable to exhaustive search. AES replaced DES after DES's short key became inadequate.
Block cipher: A symmetric-key cipher that transforms fixed-size blocks of plaintext into ciphertext. AES is one specific block cipher in this broader family.
Triple DES: A block cipher that applies DES three times with multiple keys. Triple DES extended DES's useful life before AES became the preferred replacement.
AES round function: The sequence of transformations applied to an AES state during each encryption round. Its transformations explain how AES converts plaintext into ciphertext.
Advanced Encryption Standard process: The public NIST competition that selected a successor to DES and led to AES standardization. The selection process explains why AES was openly scrutinized before adoption.
Finite field: A field containing finitely many elements, with addition, subtraction, multiplication, and division defined. AES performs key parts of its byte arithmetic in a finite field.
Serpent: A block cipher and AES competition finalist designed by Ross Anderson, Eli Biham, and Lars Knudsen. Serpent was a more conservative finalist that lost to Rijndael in the AES competition.
Rijndael key schedule: The algorithm that derives round keys from the original Rijndael cipher key. AES expands its key into round keys used throughout encryption.
Joan Daemen: A Belgian cryptographer who co-designed the Rijndael cipher with Vincent Rijmen. Daemen helped create the cipher chosen as AES.

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