AES - PowerPoint PPT Presentation

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AES

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Triple DES (112 bits) Two 56-bit keys; Same hardware/software. Encryption. C1 = DESEncrypt(P, k1) ... Most ciphers use a Feistel structure (some of the bits in ... – PowerPoint PPT presentation

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Title: AES


1
AES Ken Dewey Networking / Cyber Security Rose
State College Midwest City, OK 73110
2
Triple DES (112 bits)
  • Two 56-bit keys Same hardware/software
  • Encryption
  • C1 DESEncrypt(P, k1)
  • C2 DESDecrypt(C1, k2)
  • C3 DESEncrypt(C2, k1)
  • Decryption
  • D2 DESDecrypt(C3, k1)
  • D1 DESEncrypt(D2, k2)
  • P DESDecrypt(D1, k1)

3
Advanced Encryption Standard (AES)
  • Rijndael Algorithm (Daeman Rijmen, 2000)
  • Federal standard (FIPS 197) in December 2001
  • Features
  • A system breaking DES in 1 second would take 149
    trillion years to break a 128-bit AES key
    (smallest key size)
  • Very good performance in hardware and software
  • Wide range of computing environments
  • Variable block and key lengths, and number of
    cycles
  • Simplicity, low memory requirements, sound design
  • Suitable for ATM, HDTV, B-ISDN, voice,
    satellite(gt 1 GBits/sec requires dedicated
    hardware)

4
AES (contd)
  • Details of AES Algorithm
  • Most ciphers use a Feistel structure (some of the
    bits in intermediate states are simply
    transposed)
  • AES uses three distinct invertible uniform
    transformations (layers)
  • AES Algorithm
  • ByteSub Linear mixing layer (diffusion)
  • ShiftRow Parallel S-boxes (confusion)
  • MixColumn Shift lefts and XORs of bits not used
    in the last round (confusion and diffusion)
  • AddRoundKey XOR of key to state (confusion)

5
AES (contd)
  • Resistance to all known attacks
  • Speed, code compactness, wide range of platforms
    (including smart card applications)
  • Design simplicity Strong math foundation
  • Number of Rounds
  • Variable Block and Key sizes (4-byte words)
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