It's a very Fermat's Last Theorem type story.

So we worked hard on the problem.

And we thought at times that maybe it was impossible.

Diffie and Hellman had a set of conditions that they'd like to meet, that the public key and the private key were separate.

You couldn't tell one from the other.

And one undid what the other did, but it was infeasible seeing only the public key to come up with the private key.

So that was the basic idea of public key cryptography at the time.

Were there kind of interesting attempts to break the scheme? Were there interesting attempts at trying to prove that the scheme is secure?