Adopted in 1977 by the National Bureau of Standards, Data are encrypted in 64 bits blocks using 56 bit key. Algorithm[^1] transforms input in a series of steps to output with the same 64 bit length. The same steps and keys are used for decryption terms: - **Feistel Structure** - A network architecture in which data is divided into two parts, and only one part is modified in each round. - **S-boxes (Substitution boxes)** - Substitution tables converting 6-bit inputs to 4-bit outputs, introducing non-linearity to the algorithm. - **E Expansion** - A function expanding 32-bit input to 48 bits by repeating certain bits. - **Subkeys** - A set of 16 derivative keys, generated from the master key, used in consecutive rounds. - **PC-1 and PC-2 Permutations** - Special permutations used in the subkey generation process. - **Key Parity Bits** - In the original 64-bit DES key, every eighth bit is a parity bit used to verify key correctness. --- #Cybersecurity #TerminologyDefinitions #ConceptExplanation #Beginner [^1]: [[Cryptography and network security principles and practice (fifth edition) by William Stallings]]