ADVANCED ENCRYPTION STANDARD

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ADVANCED ENCRYPTION STANDARD

• PREPARED BY
• KRISTEN NAIR A/L SRIDERAN
• 012010030490
• VIVIANNA MUJAN AK NICHOLAS
• 012010050424

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INTRODUCTION

• The Advanced Encryption Standard(AES) is an
  encryption algorithm for securing sensitive but
  unclassified material by U.S Government agencies
  and as a likely consequence, may eventually
  become the real encryption standard for
  commercial transaction in the private sector.
• AES is based on a design principle known as a
  substitution permutation network. It is fast in
  both software and hardware. Unlike its
  predecessor, DES, AES does not use a feistel
  network.

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INTRODUCTION

• A strong encryption algorithm need only meet only
  single main criteria
• There must be no way to find the unencrypted
  clear text if the key is unknown, except brute
  force, example, to try all possible keys until
  the right one is found
• A secondary criterion must also be met
• The number of possible keys must be so large it
  is computationally infeasible to actually stage a
  successful brute force attack in short enough a
  time.

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METHOD IN ADVANCED ENCRYPTION STANDARD

• AddRoundKey
• The AddRoundKey routine is simple XOR step. It is
  the step that incorporates the round key, a
  portion of the expanded key, into the plaintext.

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METHOD IN ADVANCED ENCRYPTION STANDARD

• SubBytes
• In the SubBytes step, each byte in the matrix is
  updated using an 8-bit substitution box, the
  Rijndael S-box. This operation provides the
  non-liearity in the cipher. The S-box used is
  derived from the multiplicative inverse over
  GF(28),known to have good non-linearity
  properties, the s-box is constructed by combining
  the inverse function with an invertible affine
  transformation. The S-box is also chosen to avoid
  any fixed points(and so is a derangement), and
  also any opposite fixed points.

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METHOD IN ADVANCED ENCRYPTION STANDARD

• ShiftRows
• Arranges the state in a matrix and then performs
  a circular shift for each row. This is not a bit
  wise shift. The circular shift just moves each
  byte one space over. A byte that was in the
  second position may end up in the third position
  after the shift. The circular part of it
  specifies that the byte in the last position
  shifted one space will end up in the first
  position in hte same row.

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METHOD IN ADVANCED ENCRYPTION STANDARD

• MixColumns
• This is perhaps the hardest step to both
  understand and explain. There are two parts to
  this step. This first will explain which parts of
  the state are multiplied against which parts of
  the matrix. The second will explain how this
  multiplication is implemented over whats called
  a Galois Field.

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CONCLUSION

• There is currently no evidence that AES has any
  weakness making any attack other than exhaustive
  search, example brute force.
• There are many pitfalls to avoid when encryption
  is implemented, and keys are generated. It is
  necessary to ensure each and every
  implementations security, but hard since it
  requires careful examination by experts.
• An information aspect of an evaluation of any
  specific implementation is determine that such an
  examination has been made, or can be conducted.