ustc_sec_2015_08.sh

#!/bin/bash
feistel(){
  declare -i i l="$1" r="$2" t magic=225052
  for ((i=0; i<16; i++)); do
    printf '0x%08x,\t' "$i" "$magic" "$(( (magic + 8) & 31))" "$(( ((magic + r) << 8) & 0xFFFFFFFF ))" "$(( (magic * (b+4)) & 0xFFFFFFFF))" "$(( (26172 * r) & 0xFFFFFFFF))" "$a"
    echo
    t=r
    l=l
    r=t
    # round function
    ((r = (l ^ ((magic + l) << 8) ^ b ^ (2 * magic) ^ (l << ((magic+8) & 31)) ^ (magic * (b+4)) ^ (25998 * l + 174 * l)) &0xffffffff))
    # new key (rotate)
    ((magic = (i%3 == 1 ? ((magic << 1) | (magic >> 31)) : ((magic << 2)  | (magic >> 30))) & 0xFFFFFFFF))
  done
  echo $out_2,$out_1,dec=$magic
}
feistel 1 2