• 3DES

Data Encryption Standard (DES)

Overview

• Status: Outdated
• Type: Symmetric-Key Block Cipher, Feilstel
• Actual Key Length: 56 bits
  • The key consists of 64 bits where every eighth bit is used for parity
  • 8 bits used as checksum (Error correction)

How DES Works

• DES's encryption works as a combination of the following:
  • One-Time Pad
  • Permutation Cipher
  • substitution ciphers applied to bit sequences
• It uses the same key in both encrypting and decrypting data.
• Each 64-bit block of plaintext is encrypted to a 64-bit block of ciphertext (To prevent the danger from Frequency Analysis)

Technical Description

DES is a standard for data encryption that uses a secret key for both encryption and decryption (symmetric cryptosystem). DES uses a 64-bit secret key, of which 56 bits are generated randomly and the other 8 bits are used for error detection. It uses a data encryption algorithm (DEA), a secret key block cipher employing a 56-bit key operating on 64-bit blocks. DES is the archetypal block cipher—an algorithm that takes a fixed-length string of plaintext bits and transforms it into a ciphertext bit string of the same length.

Implementation and Usage

The design of DES allows users to implement it in hardware and use it for single-user encryption, such as to store files on a hard disk in encrypted form. DES provides 72 quadrillion or more possible encryption keys and chooses a random key for the encryption of each message. Because of the inherent weakness of DES vis-à-vis today's technologies, some organizations use triple DES (3DES), in which they repeat the process three times for added strength until they can afford to update their equipment to AES capabilities.