group 01 foucher s thontat y shaduka s n.
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Group 01 Foucher , S Thontat , Y Shaduka , S. Brute Force Cryptic Attack on DES encrypted Data. Encryption History. WWII and breaking the Enigma code 10 000 people full time. DES and Brute Force Attacks. 56 bit keys to stop Birthday Attacks 7.2 x 10^16 possibility 64 bits of Data

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Presentation Transcript
encryption history
Encryption History
  • WWII and breaking the Enigma code
  • 10 000 people full time
des and brute force attacks
DES and Brute Force Attacks
  • 56 bit keys to stop Birthday Attacks
  • 7.2 x 10^16 possibility
  • 64 bits of Data
  • Weakness (advantage):

easily implemented in HDW

cryptanalysis
Cryptanalysis
  • Partial knowledge about encoded message

“DreaGro”… (64 bits)

  • Exploit Human weaknesses

“aaaaaaa” to “9999999”

20 500 Reduction in Explored key space

probabilities
Probabilities
  • 56 bit key space: 2^56 = 7.2 * 10^16
  • Collisions Expected every:

2^(OutputSz/2) = 2^32 = 4.3 * 10^9

  • p(collision) = 2.33 * 10^-10
  • p(2 simultaneous collisions) =

8.14 * 10^-19 (Every 779 years)

  • E(collisions) = 50,794
slide9

Structure of the Encrypter

  • 18 pipelined stages
  • The first and final stages are key independent permutations
  • Encryption is performed in the 16 middle stages
  • Subkeysare applied to the middle stages in order, from K1 to K16
slide10

DES Core Algorithm

  • Feistel structure:
    • Encryption and Decryption are similar processes
  • The Feistelfunction operates on the right-half block and consists of four stages:
    • Expansion
    • Key mixing
    • Substitution
    • Permutation
slide11

Structure of the Decrypter

  • Same algorithm used for encryption/decryption
  • Subkeysare applied in reverse order, from K16 to K1
  • Keys are aged
  • Decrypted data block is applied to a look-up