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Table 6 Impossible subspace trails for SIMON. For simplicities, we denote 0000 by 0 and arbitrary four bits by ?

From: Searching for impossible subspace trails and improved impossible differential characteristics for SIMON-like block ciphers

  Rounds Impossible subspace trails
SIMON32 11 \((\textbf {0}|\textbf {0}|\textbf {0}|\textbf {0},0*00|\textbf {0}|\textbf {0}|000*) \nrightarrow (0*00|\textbf {0}|1000|000*,\textbf {0}|\textbf {0}|\textbf {0}|\textbf {0})\)
   (0|0|0|0,0*00 |0|1000|000*) \(\nrightarrow \) (0*00 |0|0|000*, 0|0|0|0)
SIMON48 12 (0|0|0|0|0|0,0|0|0|0|0|000*) \(\nrightarrow \) (1000 |0|0|000* |0*00 |0***,
   0|0|0|0|y0|000*)
   (0|0|0|0|0|000*,1000 |0|0|000* |0*00 |0***) \(\nrightarrow \) (0|0|0|0|0|
   000*, 0|0|0|0|0|0)
SIMON64 13 (0|0|0|0|0|0|0|0,0*00 |0|0|0|0|0|0|000*) \(\nrightarrow \) (0*00 |0|1000|
   000* |0*00 |0*** |*00* |?,*000 |0|0|0|0|000* |0*00 |0***)
   (*000 |0|0|0|0|000* |0*00 |0***,0*00 |0|1000|000* |0*00 |
   0*** |*00* |?) \(\nrightarrow \) (0*00 |0|0|0|0|0|0|000*, 0|0|0|0|0|0|0|0)
SIMON96 16 (0|0|0|0|0|0|0|0|0|0|0|0,0*00 |0|0|0|0|0|0|0|0|0|0|000*)
   \(\nrightarrow \) (*010 |0|0|0|0|000* |0*00 |0*** |*00* |?|0*** |?,0*00 |
   0|0|0|0|0|0|000* |0*00 |0*** |*00* |?)
   (0*00 |0|0|0|0|0|0|000* |0*00 |0*** |*00* |?,*010 |0|0|0|0|
   000* |0*00 |0*** |*00* |?|0*** |?) \(\nrightarrow \) (0*00 |0|0|0|0|0|0|0|
   0|0|0|000*, 0|0|0|0|0|0|0|0|0|0|0|0)
SIMON128 19 (0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0,0*00 |0|0|0|0|0|0|0|0|
   0|0|0|0|0|0|000*) \(\nrightarrow \) (1*00 |0|0|0|0|0|0|000* |0*00 |0*** |
   *00* |?|0*** |?|?|?,*000 |0|0|0|0|0|0|0|0|000* |0*00 |0*** |
   *00* |?|0*** |?)
   (0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0,0*00 |0|0|0|0|0|0|0|0|0|
   0|0|0|0|0|000*) \(\nrightarrow \) (1*00 |0|0|0|0|0|0|000* |0*00 |0*** |
   *00* |?|0*** |?|?|?,*010 |0|0|0|0|0|0|0|0|000* |0*00 |0*** |
   *00* |?|0*** |?)
   (*000 |0|0|0|0|0|0|0|0|000* |0*00 |0*** |*00* |?|0*** |?,
   1*00 |0|0|0|0|0|0|000* |0*00 |0*** |*00* |?|0*** |?|?|?) \(\nrightarrow \)
   (0|0|0|0|0|0|0|0|0|0|0|0|0|0|0,0*00 |0|0|0|0|0|0|0|0|
   0|0|0|0|0|0|000*)
   (*010 |0|0|0|0|0|0|0|0|000* |0*00 |0*** |*00* |?|0*** |?,
   1*00 |0|0|0|0|0|0|000* |0*00 |0*** |*00* |?|0*** |?|?|?) \(\nrightarrow \)
   (0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0,0*00 |0|0|0|0|0|0|0|0|
   0|0|0|0|0|0|000*)