Why does Neumann think cryptography isn't the solution? What did Peter G. Neumann mean by:


  If you think cryptography is the answer to your problem, then you don't know what your problem is.


(eg: quoted in the New York Times, February 20 2001)
That New York Times article actually continues after that quote:

Dr. Neumann explained that there are always ways to get around cryptography barriers and that these methods have nothing to do with breaking codes.
&quot;It's like the voting machines,&quot; he said. &quot;You'd like to have some integrity in the electoral process and now folks are coming out of the woodwork saying, `We have this perfect algorithm for privacy and security.' &quot;

So it's very clear that this is the difference between secure systems and just the cryptographic algorithms.
That said, if things are managed right then cryptography certainly has its benefits.

As another example, nobody will argue that TLS doesn't have its advantages. But even there, the huge number of Certificate Authorities and the enormous amount of trust put on them and the browser manufacturers threatens the system, even though the TLS protocol is relatively secure when implemented correctly.