Encrypt/Decrypt Message Plain text Type Something

SecretKey Encrypt Decrypt

IDEA (64)
CAST5 (64 Bits Block Siize)
AES/CBC/PKCS5Padding (128)
AES/ECB/NoPadding (128)
AES/ECB/PKCS5Padding (128)
DES/CBC/NoPadding (56)
DES/CBC/PKCS5Padding (56)
DES/ECB/NoPadding (56)
DES/ECB/PKCS5Padding (56)
DESede/CBC/NoPadding (168)
DESede/CBC/PKCS5Padding (168)
DESede/ECB/NoPadding (168)
DESede/ECB/PKCS5Padding (168)

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DES – Data Encryption Standard

  • Derived in 1972 as derivation of Lucifer algorithm developed by Horst Fiestel at IBM
  • Patented in 1974 - Block Cipher Cryptographic System
  • Commercial and non-classified systems
  • DES describes the Data Encryption Algorithm DEA
  • Federal Information Processing Standard FIPS adopted DES in 1977
  • Re-certified in 1993 by National Institute of Standards and Technology but will be replaced by AES Advanced Encryption Standard by Rijndael.
  • DES uses 64 bit block size and 56 bit key, begins with 64 bit key and strips 8 parity bits
  • DEA is 16 round cryptosystem designed for implementation in hardware
  • 56 bit key = 256 or 70 quadrillion possible keys
  • Distributed systems can break it. S. Government no longer uses it
  • Triple DES – three encryptions using DEA are now being used until AES is adopted

DES uses confusion and diffusion as suggested by Claude Shannon

Confusion conceals statistical connection

Accomplished through s-boxes

Diffusion spread the influence of plaintext character over many ciphertext characters

Accomplished through p-boxes

DES Operates in four modes

  • Electronic Code Book (ECB)
  • Cipher Block Chaining (CBC)
  • Cipher Feedback (CFB)
  • Output Feedback (OFB)

Electronic Code Book

  • Native encryption mode
  • Provides the recipe of substitutions and permutations that will be performed on the block of plaintext.
  • Data within a file does not have to be encrypted in a certain order.
  • Used for small amounts of data, like challenge-response, key management tasks.
  • Also used to encrypt PINs in ATM machines.

Cipher Block Chaining

  • Each block of text, the key, and the value based on the previous block is processed in the algorithm and applied to the next block of text.

Cipher Feedback

  • The previously generated ciphertext from the last encrypted block of data is inputted into the algorithm to generate random values.
  • These random values are processed with the current block of plaintext to create ciphertext.
  • This mode is used when encrypting individual characters is required.

Output Feedback

  • Functioning like a stream cipher by generating a stream of random binary bits to be combined with the plaintext to create ciphertext.
  • The ciphertext is fed back to the algorithm to form a portion of the next input to encrypt the next stream of bits.
  • DES has been broken with Internet network of PC’s

DES is considered vulnerable by brute force search of the key – replaced by triple DES and AES 

Triple DES

  • Double encryption is subject to meet in the middle attack
  • Encrypt on one end decrypt on the other and compare the values
  • So Triple DES is used
  • Can be done several different ways:
    • DES – EDE2 (encrypt key 1, decrypt key 2, encrypt key 1)
    • DES – EE2 (encrypt key 1, encrypt key 2, encrypt key 1)
    • DES –EE3 (encrypt key 1, encrypt key 2, encrypt key 3) - most secure
  • Advanced Encryption Standard
  • Block Cipher that will replace DES
  • Anticipated that Triple DES will remain approved for Government Use
  • AES announced by NIST in January 1997 to find replacement for DES

5 Finalists

  • MARS
  • RC6
  • Rijndael
  • Serpent
  • Blowfish