CITS3002 Computer Networks  
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The DES Algorithm

As an example of the first official deployment of encryption, we'll consider the Data Encryption Standard, DES.

In 1977 the US Government adopted a product cipher from IBM and later that year was defined as as the official encryption standard by the US Standards Bureau.

DES software is publicly available (see DES-crypt.c), but is more efficiently implemented in hardware. Users are confident of its security (they will openly say when it is in use - for example, Unix passwords).

  • Data is encrypted in 64 bit blocks.
  • Ciphertext is output in 64 bit blocks.
  • A 56 bit key is used.
  • The same key is used for both encryption and decryption.



CITS3002 Computer Networks, Lecture 12, Cryptography's role in networking, p7, 22nd May 2024.