up::[[Cryptographic Algorithms]] # Data Encryption Standard (DES) The Data Encryption Standard (DES) is a symmetric-key algorithm for the encryption of electronic data. Established in 1977 by the U.S. National Institute of Standards and Technology (NIST), DES became a federal standard and was widely adopted for commercial and government applications. ## Overview - **Block Cipher**: Operates on 64-bit blocks of data using a 56-bit key (with 8 parity bits). - **Feistel Structure**: Uses a series of permutation and substitution functions over 16 rounds. ## Key Milestones - **1973**: NIST (formerly NBS) initiated a project to develop a federal encryption standard. - **1976**: IBM's proposed cipher, named "Lucifer", was selected with modifications and renamed DES. - **1977**: Officially adopted as a federal standard (FIPS PUB 46). - **1997**: DES was publicly broken by a brute-force attack by the DESCHALL project. - **1999**: Electronic Frontier Foundation's (EFF) "Deep Crack" machine confirmed the vulnerability of DES to brute-force attacks. - **2002**: Officially deprecated by NIST and replaced by the Advanced Encryption Standard (AES). ## Strengths & Weaknesses 1. **Short Key Length**: The 56-bit key length has been proven vulnerable to brute-force attacks. 2. **S-Boxes**: DES's substitution boxes were once a source of controversy due to lack of design transparency but were later found to be resistant against differential cryptanalysis. 3. **Triple DES**: As a countermeasure to DES's vulnerabilities, 3DES was introduced, applying the DES algorithm three times with different keys. ## Legacy & Relevance Today - **Historical Significance**: DES's widespread adoption set a precedent for subsequent encryption standards. - **Legacy Usage**: Some legacy systems may still utilize DES or 3DES, though it's strongly discouraged for modern applications. - **Cryptanalysis Significance**: DES challenges led to advancements in the field of cryptanalysis, including the development of techniques like differential and linear cryptanalysis. ## Related Concepts - **Triple DES (3DES)**: An extension to counter DES's vulnerabilities. - **Advanced Encryption Standard (AES)**: Successor to DES and currently the global standard for encryption. - **Brute-Force Attack**: A method of trial and error, attempting every possible key until the correct one is found.