viff

changeset 1096:072920ec7f69

Optimization: Use lin_comb() instead of Matrix class in byte_sub().
author Marcel Keller Fri, 30 Jan 2009 14:19:54 +0100 e5bb773fb1fe 50056a810951 viff/aes.py 1 files changed, 17 insertions(+), 12 deletions(-) [+]
line diff
```     1.1 --- a/viff/aes.py	Fri Jan 30 12:33:30 2009 +0100
1.2 +++ b/viff/aes.py	Fri Jan 30 14:19:54 2009 +0100
1.3 @@ -88,15 +88,15 @@
1.4          self.runtime = runtime
1.5          self.use_exponentiation = use_exponentiation
1.6
1.7 -    # matrix for byte_sub
1.8 -    A = Matrix([[1,0,0,0,1,1,1,1],
1.9 -                [1,1,0,0,0,1,1,1],
1.10 -                [1,1,1,0,0,0,1,1],
1.11 -                [1,1,1,1,0,0,0,1],
1.12 -                [1,1,1,1,1,0,0,0],
1.13 -                [0,1,1,1,1,1,0,0],
1.14 -                [0,0,1,1,1,1,1,0],
1.15 -                [0,0,0,1,1,1,1,1]])
1.16 +    # matrix for byte_sub, the last column is the translation vector
1.17 +    A = Matrix([[1,0,0,0,1,1,1,1, 1],
1.18 +                [1,1,0,0,0,1,1,1, 1],
1.19 +                [1,1,1,0,0,0,1,1, 0],
1.20 +                [1,1,1,1,0,0,0,1, 0],
1.21 +                [1,1,1,1,1,0,0,0, 0],
1.22 +                [0,1,1,1,1,1,0,0, 1],
1.23 +                [0,0,1,1,1,1,1,0, 1],
1.24 +                [0,0,0,1,1,1,1,1, 0]])
1.25
1.26      def byte_sub(self, state, use_lin_comb=True):
1.27          """ByteSub operation of Rijndael.
1.28 @@ -158,14 +158,19 @@
1.29              for i in range(len(row)):
1.30                  bits = bit_decompose(invert(row[i]))
1.31
1.32 -                # caution: order is lsb first
1.33 -                vector = AES.A * Matrix(zip(bits)) + Matrix(zip([1,1,0,0,0,1,1,0]))
1.34 -                bits = zip(*vector.rows)[0]
1.35 +                # include the translation in the matrix multiplication
1.36 +                # (see definition of AES.A)
1.37 +                bits.append(GF256(1))
1.38
1.39                  if (use_lin_comb):
1.40 +                    bits = [self.runtime.lin_comb(AES.A.rows[j], bits)
1.41 +                            for j in range(len(bits) - 1)]
1.42                      row[i] = self.runtime.lin_comb(
1.43                          [2**j for j in range(len(bits))], bits)
1.44                  else:
1.45 +                    # caution: order is lsb first
1.46 +                    vector = AES.A * Matrix(zip(bits))
1.47 +                    bits = zip(*vector.rows)[0]
1.48                      row[i] = reduce(lambda x,y: x + y,
1.49                                      [bits[j] * 2**j for j in range(len(bits))])
1.50
```