Each operation performs a nonlinear function on three of a, b, c,and d.

      F(X,Y,Z) = XY v not(X) Z
      G(X,Y,Z) = XZ v Y not(Z)
      H(X,Y,Z) = X xor Y xor Z
      I(X,Y,Z) = Y xor (X v not(Z))

So MD5 Algorithm is nonlinear?

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    $\begingroup$ Welcome to Cryptography.SE. Do you know what is linear and non-linear? What operations can be linear? And, do you know what will happen a linear cryptographic algorithm? $\endgroup$ – kelalaka Apr 19 at 13:23
  • $\begingroup$ I think y=x is linear and y = x^2 is non-linear,a linear cryptographc algorithm can not be hash algorithm,I don't know what operations can be linear. $\endgroup$ – cuthead Apr 19 at 13:29
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    $\begingroup$ Usually a function $f$ is linear if $f(a+b) = f(a) + f(b)$. This is not a desirable property of any cryptographic hash function. $\endgroup$ – bmm6o Apr 19 at 15:59
  • $\begingroup$ if a hash function was linear, would it be useful? $\endgroup$ – user253751 Apr 19 at 16:35
  • $\begingroup$ A linear hash function could have an easy collision and pre-images. $\endgroup$ – kelalaka Apr 19 at 16:50

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