Generating S-box

• Properties:

  • differential characteristics
  • linear characteristics
  • nonlinear order

• Generated from DES S-box in a deterministic manner.

• Algorithm

sbox[32][16] contain 8 DES S-box; serpent[16] is random 4-bit array

index := 0

repeat

currentsbox:= index mod 32;

for i:=0 to 15 do

j:= sbox[(currentsbox+1) mod 32][serpent[i]];

swapentries (sbox[currentsbox][i], sbox[currentsbox][j]);

if sbox[currentsbox][.] has the desired properties, save it;

index := index+1;

until 8 S-box have been generated

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