Data%20Encryption%20Standard

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Data Encryption Standard
A presentation on the

• Nicolas Rowcroft
• Final Year Electronics Communication
  Engineering Honours Student
• University of Tasmania

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Outline

• History of the DES
• Data Encryption principles
• How DES works
• Triple DES
• Project

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History of DES

• Designed by IBM during the 1970s.
• Made standard in 1977 by NBS (US)
• No longer considered secure, but still widespread
• 3-DES latest standard accepted in late 1999 as
  reaffirmation of DES.

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Data Encryption Principles

• Modern encryption algorithms assume that anybody
  can gain access to the encrypted data, and to the
  algorithm itself.
• The security of most modern algorithm is in the
  key.

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Data Encryption Principles

• Key is a piece of data (usually unique to each
  user) used to manipulate original data
• Public Key algorithms Different keys for
  encryption and decryption.
• Private Key algorithms Same key used for
  encryption and decryption.
• DES is a private key algorithm.

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How DES Works (1)

• DES is designed for implementation in hardware
• Uses 64-bit key
• 8 Bits of key are discarded, so effective key
  length is 56-bit.

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How DES Works (2)

• Calculate 16 sub-keys from 64-Bit key
• 64-Bit input block undergoes initial permutation
• Split into left and right halves

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How DES Works (3)

• Each iteration (performed 16 times)
• Function of right half and sub-key is XORed with
  left half to form new left half
• Old right half forms new left half.
• Output from final iteration undergoes inverse
  initial permutation.
• To decrypt, same algorithm is used, but sub-keys
  are applied in reverse order.

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DES Functional Diagram
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Function Calculation
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Key Calculation
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Triple-DES (3-DES)

• NIST Standard uses 3 keys (K1, K2, K3) as follows
  (Encryption)
• Encrypt with first key
• Decrypt with second key
• Encrypt with third key
• Decryption is then as follows
• Decrypt with third key
• Encrypt with second key
• Decrypt with first key

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Triple DES (3-DES)

• The standard provides 3 keying options
• Option 1 K1, K2 and K3 are independent
• Option 2 K1, K2 are independent, K3 K1
• Option 3 K1 K2 K3

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Project

• I intend to design and implement a DES hardware
  architecture using VHDL design tools.
• If time permits, I intend to modify the
  architecture to incorporate 3-DES on real-time
  voice data.

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References

• NIST FIPS Publication 46-3 entitled Data
  Encryption Standard (DES). Reaffirmed 1999.
• Schneier, Bruce. Applied Cryptography Second
  Edition. John Wiley Sons Inc. 1996.