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Construction

Number of rounds for SKINNY-n-t, with n-bit internal state and t-bit tweakey state.

Tweakey Size t
Block Size n n 2n 3n
64 32 36 40
128 40 48 56

The SKINNY round function applies five different transformations: SubCells (SC), AddConstants (AC), AddRoundTweakey (ART), ShiftRows (SR) and MixColumns (MC). SKINNY Round

  • Tweakey Schedule
  • SubCells (SC): Depending on the block size, a 4-bit Sbox (for 64-bit block) or a 8-bit Sbox (for 128-bit block) is used.
  • AddConstants (AC): Some round-dependent constants are XORed to the first nibbles/bytes column of the cipher internal state.
  • AddRoundTweakey (ART): Half a block is extracted from the tweakey state and XORed to the cipher internal state. The tweakey nibbles/bytes are permuted and updated with simple LFSRs.
  • ShiftRows (SR): The nibbles/bytes of the cipher internal state are rotated to the right row-wise by some specified number of positions.
  • MixColumns (MC): Each nibbles/bytes column of the cipher internal state are multiplied by a binary matrix.