| 摘要 |
<p>A ciphering apparatus of common key type, wherein a plurality of rounding units are connected in cascade, the i-th rounding unit is fed with input data Li, Ri, the input data Ri are subjected to nonlinear transformation by a nonlinear function unit depending upon the key data, the exclusive-OR output of the output of the nonlinear function unit and the input data Li is outputted as data Ri+1 to the (i+1)-th rounding unit, and the input data Ri are outputted as data Li+1 to the (i+1)-th rounding unit. The nonlinear function unit includes: a key-dependent linear transforming unit for subjecting the input Ri to key-dependent linear transformation; a dividing unit for dividing the output into four data in0, in1, in2 and in3; first nonlinear transforming units for subjecting the divided data to nonlinear transformation to output data mid00, mid01, mid02 and mid03; a key-dependent linear transforming unit for correlating these transformed outputs to each other and subjecting them to linear transformation based upon the key data to output data mid10, mid11, mid12 and mid13; second nonlinear trasnforming units for subjecting the transformed outputs to nonlinear transformation to output data out0, out1, out2 and out3; and a coupling unit for coupling the transformed outputs to output data Y.</p> |
